[v2,RESEND,1/5] dt-bindings: soc: samsung: Add Exynos USI bindings

Add constants for choosing USIv2 configuration mode in device tree.
Those are further used in USI driver to figure out which value to write
into SW_CONF register. Also document USIv2 IP-core bindings.

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
---
Changes in v2:
  - Combined dt-bindings doc and dt-bindings header patches
  - Added i2c node to example in bindings doc
  - Added mentioning of shared internal circuits
  - Added USI_V2_NONE value to bindings header

 .../bindings/soc/samsung/exynos-usi.yaml      | 135 ++++++++++++++++++
 include/dt-bindings/soc/samsung,exynos-usi.h  |  17 +++
 2 files changed, 152 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml
 create mode 100644 include/dt-bindings/soc/samsung,exynos-usi.h

On Tue, 30 Nov 2021 13:13:21 +0200, Sam Protsenko wrote:
> Add constants for choosing USIv2 configuration mode in device tree.
> Those are further used in USI driver to figure out which value to write
> into SW_CONF register. Also document USIv2 IP-core bindings.
> 
> Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
> ---
> Changes in v2:
>   - Combined dt-bindings doc and dt-bindings header patches
>   - Added i2c node to example in bindings doc
>   - Added mentioning of shared internal circuits
>   - Added USI_V2_NONE value to bindings header
> 
>  .../bindings/soc/samsung/exynos-usi.yaml      | 135 ++++++++++++++++++
>  include/dt-bindings/soc/samsung,exynos-usi.h  |  17 +++
>  2 files changed, 152 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml
>  create mode 100644 include/dt-bindings/soc/samsung,exynos-usi.h
> 

My bot found errors running 'make DT_CHECKER_FLAGS=-m dt_binding_check'
on your patch (DT_CHECKER_FLAGS is new in v5.13):

yamllint warnings/errors:

dtschema/dtc warnings/errors:
Documentation/devicetree/bindings/soc/samsung/exynos-usi.example.dts:35.39-42.15: Warning (unique_unit_address): /example-0/usi@138200c0/serial@13820000: duplicate unit-address (also used in node /example-0/usi@138200c0/i2c@13820000)
Documentation/devicetree/bindings/soc/samsung/exynos-usi.example.dt.yaml:0:0: /example-0/usi@138200c0/i2c@13820000: failed to match any schema with compatible: ['samsung,exynosautov9-hsi2c']

doc reference errors (make refcheckdocs):

See https://patchwork.ozlabs.org/patch/1561571

This check can fail if there are any dependencies. The base for a patch
series is generally the most recent rc1.

If you already ran 'make dt_binding_check' and didn't see the above
error(s), then make sure 'yamllint' is installed and dt-schema is up to
date:

pip3 install dtschema --upgrade

Please check and re-submit.

On Tue, Nov 30, 2021 at 01:13:21PM +0200, Sam Protsenko wrote:
> Add constants for choosing USIv2 configuration mode in device tree.
> Those are further used in USI driver to figure out which value to write
> into SW_CONF register. Also document USIv2 IP-core bindings.
> 
> Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
> ---
> Changes in v2:
>   - Combined dt-bindings doc and dt-bindings header patches
>   - Added i2c node to example in bindings doc
>   - Added mentioning of shared internal circuits
>   - Added USI_V2_NONE value to bindings header
> 
>  .../bindings/soc/samsung/exynos-usi.yaml      | 135 ++++++++++++++++++
>  include/dt-bindings/soc/samsung,exynos-usi.h  |  17 +++
>  2 files changed, 152 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml
>  create mode 100644 include/dt-bindings/soc/samsung,exynos-usi.h
> 
> diff --git a/Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml b/Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml
> new file mode 100644
> index 000000000000..a822bc62b3cd
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml
> @@ -0,0 +1,135 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/soc/samsung/exynos-usi.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Samsung's Exynos USI (Universal Serial Interface) binding
> +
> +maintainers:
> +  - Sam Protsenko <semen.protsenko@linaro.org>
> +  - Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
> +
> +description: |
> +  USI IP-core provides selectable serial protocol (UART, SPI or High-Speed I2C).
> +  USI shares almost all internal circuits within each protocol, so only one
> +  protocol can be chosen at a time. USI is modeled as a node with zero or more
> +  child nodes, each representing a serial sub-node device. The mode setting
> +  selects which particular function will be used.
> +
> +  Refer to next bindings documentation for information on protocol subnodes that
> +  can exist under USI node:
> +
> +  [1] Documentation/devicetree/bindings/serial/samsung_uart.yaml
> +  [2] Documentation/devicetree/bindings/i2c/i2c-exynos5.txt
> +  [3] Documentation/devicetree/bindings/spi/spi-samsung.txt
> +
> +properties:
> +  $nodename:
> +    pattern: "^usi@[0-9a-f]+$"
> +
> +  compatible:
> +    const: samsung,exynos-usi-v2

Use SoC based compatibles.

> +
> +  reg:
> +    maxItems: 1
> +
> +  clocks:
> +    items:
> +      - description: Bus (APB) clock
> +      - description: Operating clock for UART/SPI/I2C protocol
> +
> +  clock-names:
> +    items:
> +      - const: pclk
> +      - const: ipclk
> +
> +  ranges: true
> +
> +  "#address-cells":
> +    const: 1
> +
> +  "#size-cells":
> +    const: 1
> +
> +  samsung,sysreg:
> +    $ref: /schemas/types.yaml#/definitions/phandle-array
> +    description:
> +      Should be phandle/offset pair. The phandle to System Register syscon node
> +      (for the same domain where this USI controller resides) and the offset
> +      of SW_CONF register for this USI controller.
> +
> +  samsung,mode:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description:
> +      Selects USI function (which serial protocol to use). Refer to
> +      <include/dt-bindings/soc/samsung,exynos-usi.h> for valid USI mode values.

This seems to be redundant. Just check which child is enabled.

> +
> +  samsung,clkreq-on:
> +    type: boolean
> +    description:
> +      Enable this property if underlying protocol requires the clock to be
> +      continuously provided without automatic gating. As suggested by SoC
> +      manual, it should be set in case of SPI/I2C slave, UART Rx and I2C
> +      multi-master mode. Usually this property is needed if USI mode is set
> +      to "UART".
> +
> +      This property is optional.
> +
> +patternProperties:
> +  # All other properties should be child nodes
> +  "^.*@[0-9a-f]+$":

Only 'serial', 'spi', or 'i2c' are valid.

> +    type: object
> +    description: Child node describing underlying USI serial protocol
> +
> +required:
> +  - compatible
> +  - reg
> +  - clocks
> +  - clock-names
> +  - ranges
> +  - "#address-cells"
> +  - "#size-cells"
> +  - samsung,sysreg
> +  - samsung,mode
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/interrupt-controller/arm-gic.h>
> +    #include <dt-bindings/soc/samsung,exynos-usi.h>
> +
> +    usi0: usi@138200c0 {
> +        compatible = "samsung,exynos-usi-v2";
> +        reg = <0x138200c0 0x20>;
> +        samsung,sysreg = <&sysreg_peri 0x1010>;
> +        samsung,mode = <USI_V2_UART>;
> +        samsung,clkreq-on; /* needed for UART mode */
> +        #address-cells = <1>;
> +        #size-cells = <1>;
> +        ranges;
> +        clocks = <&cmu_peri 32>, <&cmu_peri 31>;
> +        clock-names = "pclk", "ipclk";
> +        status = "disabled";

Why are you disabling your example? Remove status.

> +
> +        serial_0: serial@13820000 {
> +            compatible = "samsung,exynos850-uart";
> +            reg = <0x13820000 0xc0>;
> +            interrupts = <GIC_SPI 227 IRQ_TYPE_LEVEL_HIGH>;
> +            clocks = <&cmu_peri 32>, <&cmu_peri 31>;
> +            clock-names = "uart", "clk_uart_baud0";
> +            status = "disabled";
> +        };
> +
> +        hsi2c_0: i2c@13820000 {
> +            compatible = "samsung,exynosautov9-hsi2c";
> +            reg = <0x13820000 0xc0>;
> +            interrupts = <GIC_SPI 227 IRQ_TYPE_LEVEL_HIGH>;
> +            #address-cells = <1>;
> +            #size-cells = <0>;
> +            clocks = <&cmu_peri 32>, <&cmu_peri 31>;
> +            clock-names = "hsi2c_pclk", "hsi2c";
> +            status = "disabled";
> +        };
> +    };
> diff --git a/include/dt-bindings/soc/samsung,exynos-usi.h b/include/dt-bindings/soc/samsung,exynos-usi.h
> new file mode 100644
> index 000000000000..a01af169d249
> --- /dev/null
> +++ b/include/dt-bindings/soc/samsung,exynos-usi.h
> @@ -0,0 +1,17 @@
> +/* SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) */
> +/*
> + * Copyright (c) 2021 Linaro Ltd.
> + * Author: Sam Protsenko <semen.protsenko@linaro.org>
> + *
> + * Device Tree bindings for Samsung Exynos USI (Universal Serial Interface).
> + */
> +
> +#ifndef __DT_BINDINGS_SAMSUNG_EXYNOS_USI_H
> +#define __DT_BINDINGS_SAMSUNG_EXYNOS_USI_H
> +
> +#define USI_V2_NONE		0
> +#define USI_V2_UART		1
> +#define USI_V2_SPI		2
> +#define USI_V2_I2C		3
> +
> +#endif /* __DT_BINDINGS_SAMSUNG_EXYNOS_USI_H */
> -- 
> 2.30.2
> 
>

On 30/11/2021 18:43, Rob Herring wrote:
> On Tue, 30 Nov 2021 13:13:21 +0200, Sam Protsenko wrote:
>> Add constants for choosing USIv2 configuration mode in device tree.
>> Those are further used in USI driver to figure out which value to write
>> into SW_CONF register. Also document USIv2 IP-core bindings.
>>
>> Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
>> ---
>> Changes in v2:
>>   - Combined dt-bindings doc and dt-bindings header patches
>>   - Added i2c node to example in bindings doc
>>   - Added mentioning of shared internal circuits
>>   - Added USI_V2_NONE value to bindings header
>>
>>  .../bindings/soc/samsung/exynos-usi.yaml      | 135 ++++++++++++++++++
>>  include/dt-bindings/soc/samsung,exynos-usi.h  |  17 +++
>>  2 files changed, 152 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml
>>  create mode 100644 include/dt-bindings/soc/samsung,exynos-usi.h
>>
> 
> My bot found errors running 'make DT_CHECKER_FLAGS=-m dt_binding_check'
> on your patch (DT_CHECKER_FLAGS is new in v5.13):
> 
> yamllint warnings/errors:
> 
> dtschema/dtc warnings/errors:
> Documentation/devicetree/bindings/soc/samsung/exynos-usi.example.dts:35.39-42.15: Warning (unique_unit_address): /example-0/usi@138200c0/serial@13820000: duplicate unit-address (also used in node /example-0/usi@138200c0/i2c@13820000)

Rob,

The checker complains about two nodes with same unit-address, even
though the node name is different. Does it mean that our idea of
embedding two children in USI and having enabled only one (used one) is
wrong?

  usi0: usi@138200c0 {
    // enabled device/child
    serial@13820000 {
      status = "okay";
    };

    // disabled device, keep for reference and for boards which
    // would like to use it
    i2c@13820000 {
      status = "disabled";
    };
  };


Best regards,
Krzysztof

On Tue, Nov 30, 2021 at 2:04 PM Krzysztof Kozlowski
<krzysztof.kozlowski@canonical.com> wrote:
>
> On 30/11/2021 18:43, Rob Herring wrote:
> > On Tue, 30 Nov 2021 13:13:21 +0200, Sam Protsenko wrote:
> >> Add constants for choosing USIv2 configuration mode in device tree.
> >> Those are further used in USI driver to figure out which value to write
> >> into SW_CONF register. Also document USIv2 IP-core bindings.
> >>
> >> Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
> >> ---
> >> Changes in v2:
> >>   - Combined dt-bindings doc and dt-bindings header patches
> >>   - Added i2c node to example in bindings doc
> >>   - Added mentioning of shared internal circuits
> >>   - Added USI_V2_NONE value to bindings header
> >>
> >>  .../bindings/soc/samsung/exynos-usi.yaml      | 135 ++++++++++++++++++
> >>  include/dt-bindings/soc/samsung,exynos-usi.h  |  17 +++
> >>  2 files changed, 152 insertions(+)
> >>  create mode 100644 Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml
> >>  create mode 100644 include/dt-bindings/soc/samsung,exynos-usi.h
> >>
> >
> > My bot found errors running 'make DT_CHECKER_FLAGS=-m dt_binding_check'
> > on your patch (DT_CHECKER_FLAGS is new in v5.13):
> >
> > yamllint warnings/errors:
> >
> > dtschema/dtc warnings/errors:
> > Documentation/devicetree/bindings/soc/samsung/exynos-usi.example.dts:35.39-42.15: Warning (unique_unit_address): /example-0/usi@138200c0/serial@13820000: duplicate unit-address (also used in node /example-0/usi@138200c0/i2c@13820000)
>
> Rob,
>
> The checker complains about two nodes with same unit-address, even
> though the node name is different. Does it mean that our idea of
> embedding two children in USI and having enabled only one (used one) is
> wrong?

IIRC, we allow for this exact scenario, and there was a change in dtc
for it. So I'm not sure why this triggered.

Rob

On Thu, Dec 2, 2021 at 5:01 AM Sam Protsenko <semen.protsenko@linaro.org> wrote:
>
> On Wed, 1 Dec 2021 at 18:20, Rob Herring <robh@kernel.org> wrote:
> >
> > On Tue, Nov 30, 2021 at 2:04 PM Krzysztof Kozlowski
> > <krzysztof.kozlowski@canonical.com> wrote:
> > >
> > > On 30/11/2021 18:43, Rob Herring wrote:
> > > > On Tue, 30 Nov 2021 13:13:21 +0200, Sam Protsenko wrote:
> > > >> Add constants for choosing USIv2 configuration mode in device tree.
> > > >> Those are further used in USI driver to figure out which value to write
> > > >> into SW_CONF register. Also document USIv2 IP-core bindings.
> > > >>
> > > >> Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
> > > >> ---
> > > >> Changes in v2:
> > > >>   - Combined dt-bindings doc and dt-bindings header patches
> > > >>   - Added i2c node to example in bindings doc
> > > >>   - Added mentioning of shared internal circuits
> > > >>   - Added USI_V2_NONE value to bindings header
> > > >>
> > > >>  .../bindings/soc/samsung/exynos-usi.yaml      | 135 ++++++++++++++++++
> > > >>  include/dt-bindings/soc/samsung,exynos-usi.h  |  17 +++
> > > >>  2 files changed, 152 insertions(+)
> > > >>  create mode 100644 Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml
> > > >>  create mode 100644 include/dt-bindings/soc/samsung,exynos-usi.h
> > > >>
> > > >
> > > > My bot found errors running 'make DT_CHECKER_FLAGS=-m dt_binding_check'
> > > > on your patch (DT_CHECKER_FLAGS is new in v5.13):
> > > >
> > > > yamllint warnings/errors:
> > > >
> > > > dtschema/dtc warnings/errors:
> > > > Documentation/devicetree/bindings/soc/samsung/exynos-usi.example.dts:35.39-42.15: Warning (unique_unit_address): /example-0/usi@138200c0/serial@13820000: duplicate unit-address (also used in node /example-0/usi@138200c0/i2c@13820000)
> > >
> > > Rob,
> > >
> > > The checker complains about two nodes with same unit-address, even
> > > though the node name is different. Does it mean that our idea of
> > > embedding two children in USI and having enabled only one (used one) is
> > > wrong?
> >
> > IIRC, we allow for this exact scenario, and there was a change in dtc
> > for it. So I'm not sure why this triggered.
> >
>
> It's triggered from WARNING(unique_unit_address, ...), because it
> calls static void check_unique_unit_address_common() function with
> disable_check=false. I guess we should interpret that this way: the
> warning makes sense in regular case, when having the same unit address
> for two nodes is wrong. So the warning is reasonable, it's just not
> relevant in this particular case. What can be done:
>
>   1. We can introduce some specific property to mark nodes with
> duplicated address as intentional. check_unique_unit_address_common()
> can be extended then to omit checking the nodes if that property is
> present.
>   2. We can just ignore that warning in this particular case (and
> similar cases).
>   3. We can add some disambiguation note to that warning message, like
> "if it's intentional -- please ignore this message"
>
> I'm all for option (3), as it's the easiest one, and still reasonable.
> Rob, what do you think? Can we just ignore that warning in further
> versions of this patch series?

Just change the dtc flags to '-Wno-unique_unit_address
-Wunique_unit_address_if_enabled' for both examples and dtbs.

Rob

On Thu, 2 Dec 2021 at 22:44, Rob Herring <robh@kernel.org> wrote:
>
> On Thu, Dec 2, 2021 at 5:01 AM Sam Protsenko <semen.protsenko@linaro.org> wrote:
> >
> > On Wed, 1 Dec 2021 at 18:20, Rob Herring <robh@kernel.org> wrote:
> > >
> > > On Tue, Nov 30, 2021 at 2:04 PM Krzysztof Kozlowski
> > > <krzysztof.kozlowski@canonical.com> wrote:
> > > >
> > > > On 30/11/2021 18:43, Rob Herring wrote:
> > > > > On Tue, 30 Nov 2021 13:13:21 +0200, Sam Protsenko wrote:
> > > > >> Add constants for choosing USIv2 configuration mode in device tree.
> > > > >> Those are further used in USI driver to figure out which value to write
> > > > >> into SW_CONF register. Also document USIv2 IP-core bindings.
> > > > >>
> > > > >> Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
> > > > >> ---
> > > > >> Changes in v2:
> > > > >>   - Combined dt-bindings doc and dt-bindings header patches
> > > > >>   - Added i2c node to example in bindings doc
> > > > >>   - Added mentioning of shared internal circuits
> > > > >>   - Added USI_V2_NONE value to bindings header
> > > > >>
> > > > >>  .../bindings/soc/samsung/exynos-usi.yaml      | 135 ++++++++++++++++++
> > > > >>  include/dt-bindings/soc/samsung,exynos-usi.h  |  17 +++
> > > > >>  2 files changed, 152 insertions(+)
> > > > >>  create mode 100644 Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml
> > > > >>  create mode 100644 include/dt-bindings/soc/samsung,exynos-usi.h
> > > > >>
> > > > >
> > > > > My bot found errors running 'make DT_CHECKER_FLAGS=-m dt_binding_check'
> > > > > on your patch (DT_CHECKER_FLAGS is new in v5.13):
> > > > >
> > > > > yamllint warnings/errors:
> > > > >
> > > > > dtschema/dtc warnings/errors:
> > > > > Documentation/devicetree/bindings/soc/samsung/exynos-usi.example.dts:35.39-42.15: Warning (unique_unit_address): /example-0/usi@138200c0/serial@13820000: duplicate unit-address (also used in node /example-0/usi@138200c0/i2c@13820000)
> > > >
> > > > Rob,
> > > >
> > > > The checker complains about two nodes with same unit-address, even
> > > > though the node name is different. Does it mean that our idea of
> > > > embedding two children in USI and having enabled only one (used one) is
> > > > wrong?
> > >
> > > IIRC, we allow for this exact scenario, and there was a change in dtc
> > > for it. So I'm not sure why this triggered.
> > >
> >
> > It's triggered from WARNING(unique_unit_address, ...), because it
> > calls static void check_unique_unit_address_common() function with
> > disable_check=false. I guess we should interpret that this way: the
> > warning makes sense in regular case, when having the same unit address
> > for two nodes is wrong. So the warning is reasonable, it's just not
> > relevant in this particular case. What can be done:
> >
> >   1. We can introduce some specific property to mark nodes with
> > duplicated address as intentional. check_unique_unit_address_common()
> > can be extended then to omit checking the nodes if that property is
> > present.
> >   2. We can just ignore that warning in this particular case (and
> > similar cases).
> >   3. We can add some disambiguation note to that warning message, like
> > "if it's intentional -- please ignore this message"
> >
> > I'm all for option (3), as it's the easiest one, and still reasonable.
> > Rob, what do you think? Can we just ignore that warning in further
> > versions of this patch series?
>
> Just change the dtc flags to '-Wno-unique_unit_address
> -Wunique_unit_address_if_enabled' for both examples and dtbs.
>

Thanks. Submitted that separately from this series: [1].

[1] https://lkml.org/lkml/2021/12/3/762

> Rob

On Tue, 30 Nov 2021 at 21:31, Rob Herring <robh@kernel.org> wrote:
>
> On Tue, Nov 30, 2021 at 01:13:21PM +0200, Sam Protsenko wrote:
> > Add constants for choosing USIv2 configuration mode in device tree.
> > Those are further used in USI driver to figure out which value to write
> > into SW_CONF register. Also document USIv2 IP-core bindings.
> >
> > Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
> > ---
> > Changes in v2:
> >   - Combined dt-bindings doc and dt-bindings header patches
> >   - Added i2c node to example in bindings doc
> >   - Added mentioning of shared internal circuits
> >   - Added USI_V2_NONE value to bindings header
> >
> >  .../bindings/soc/samsung/exynos-usi.yaml      | 135 ++++++++++++++++++
> >  include/dt-bindings/soc/samsung,exynos-usi.h  |  17 +++
> >  2 files changed, 152 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml
> >  create mode 100644 include/dt-bindings/soc/samsung,exynos-usi.h
> >
> > diff --git a/Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml b/Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml
> > new file mode 100644
> > index 000000000000..a822bc62b3cd
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml
> > @@ -0,0 +1,135 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/soc/samsung/exynos-usi.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Samsung's Exynos USI (Universal Serial Interface) binding
> > +
> > +maintainers:
> > +  - Sam Protsenko <semen.protsenko@linaro.org>
> > +  - Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
> > +
> > +description: |
> > +  USI IP-core provides selectable serial protocol (UART, SPI or High-Speed I2C).
> > +  USI shares almost all internal circuits within each protocol, so only one
> > +  protocol can be chosen at a time. USI is modeled as a node with zero or more
> > +  child nodes, each representing a serial sub-node device. The mode setting
> > +  selects which particular function will be used.
> > +
> > +  Refer to next bindings documentation for information on protocol subnodes that
> > +  can exist under USI node:
> > +
> > +  [1] Documentation/devicetree/bindings/serial/samsung_uart.yaml
> > +  [2] Documentation/devicetree/bindings/i2c/i2c-exynos5.txt
> > +  [3] Documentation/devicetree/bindings/spi/spi-samsung.txt
> > +
> > +properties:
> > +  $nodename:
> > +    pattern: "^usi@[0-9a-f]+$"
> > +
> > +  compatible:
> > +    const: samsung,exynos-usi-v2
>
> Use SoC based compatibles.
>

In this particular case, I'd really prefer to have it like this. Most
likely we'll only have USIv1 and USIv1 in the end, and I think that
would be more clear to have USI version in compatible, rather than SoC
name. Please let me know if you have a strong opinion on this one --
if so I'll re-send.

> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  clocks:
> > +    items:
> > +      - description: Bus (APB) clock
> > +      - description: Operating clock for UART/SPI/I2C protocol
> > +
> > +  clock-names:
> > +    items:
> > +      - const: pclk
> > +      - const: ipclk
> > +
> > +  ranges: true
> > +
> > +  "#address-cells":
> > +    const: 1
> > +
> > +  "#size-cells":
> > +    const: 1
> > +
> > +  samsung,sysreg:
> > +    $ref: /schemas/types.yaml#/definitions/phandle-array
> > +    description:
> > +      Should be phandle/offset pair. The phandle to System Register syscon node
> > +      (for the same domain where this USI controller resides) and the offset
> > +      of SW_CONF register for this USI controller.
> > +
> > +  samsung,mode:
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    description:
> > +      Selects USI function (which serial protocol to use). Refer to
> > +      <include/dt-bindings/soc/samsung,exynos-usi.h> for valid USI mode values.
>
> This seems to be redundant. Just check which child is enabled.
>

I think it's not that easy. Soon we'll have USIv1 support added, and
that has some weird configurations, like having dual I2C mode (two
child I2C nodes must be enabled) and UART+I2C mode, etc. Looks like it
might take some not very elegant logic to figure out which exactly
mode value should be written in SW_CONF register in that way, it's
much easier to just specify mode in USI node. Also, that reflects
hardware better: we actually write that specified mode to SW_CONF
register. Also, later we might want to be able to switch that mode via
SysFS, e.g. for testing purposes. Current design seems to be better
suited for some things like that.

Please let me know if you have a strong opinion on this one, or it's
ok to leave it as is.

All other comments are addressed and will be present in v3. Thanks for
the review!

> > +
> > +  samsung,clkreq-on:
> > +    type: boolean
> > +    description:
> > +      Enable this property if underlying protocol requires the clock to be
> > +      continuously provided without automatic gating. As suggested by SoC
> > +      manual, it should be set in case of SPI/I2C slave, UART Rx and I2C
> > +      multi-master mode. Usually this property is needed if USI mode is set
> > +      to "UART".
> > +
> > +      This property is optional.
> > +
> > +patternProperties:
> > +  # All other properties should be child nodes
> > +  "^.*@[0-9a-f]+$":
>
> Only 'serial', 'spi', or 'i2c' are valid.
>
> > +    type: object
> > +    description: Child node describing underlying USI serial protocol
> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +  - clocks
> > +  - clock-names
> > +  - ranges
> > +  - "#address-cells"
> > +  - "#size-cells"
> > +  - samsung,sysreg
> > +  - samsung,mode
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > +  - |
> > +    #include <dt-bindings/interrupt-controller/arm-gic.h>
> > +    #include <dt-bindings/soc/samsung,exynos-usi.h>
> > +
> > +    usi0: usi@138200c0 {
> > +        compatible = "samsung,exynos-usi-v2";
> > +        reg = <0x138200c0 0x20>;
> > +        samsung,sysreg = <&sysreg_peri 0x1010>;
> > +        samsung,mode = <USI_V2_UART>;
> > +        samsung,clkreq-on; /* needed for UART mode */
> > +        #address-cells = <1>;
> > +        #size-cells = <1>;
> > +        ranges;
> > +        clocks = <&cmu_peri 32>, <&cmu_peri 31>;
> > +        clock-names = "pclk", "ipclk";
> > +        status = "disabled";
>
> Why are you disabling your example? Remove status.
>
> > +
> > +        serial_0: serial@13820000 {
> > +            compatible = "samsung,exynos850-uart";
> > +            reg = <0x13820000 0xc0>;
> > +            interrupts = <GIC_SPI 227 IRQ_TYPE_LEVEL_HIGH>;
> > +            clocks = <&cmu_peri 32>, <&cmu_peri 31>;
> > +            clock-names = "uart", "clk_uart_baud0";
> > +            status = "disabled";
> > +        };
> > +
> > +        hsi2c_0: i2c@13820000 {
> > +            compatible = "samsung,exynosautov9-hsi2c";
> > +            reg = <0x13820000 0xc0>;
> > +            interrupts = <GIC_SPI 227 IRQ_TYPE_LEVEL_HIGH>;
> > +            #address-cells = <1>;
> > +            #size-cells = <0>;
> > +            clocks = <&cmu_peri 32>, <&cmu_peri 31>;
> > +            clock-names = "hsi2c_pclk", "hsi2c";
> > +            status = "disabled";
> > +        };
> > +    };
> > diff --git a/include/dt-bindings/soc/samsung,exynos-usi.h b/include/dt-bindings/soc/samsung,exynos-usi.h
> > new file mode 100644
> > index 000000000000..a01af169d249
> > --- /dev/null
> > +++ b/include/dt-bindings/soc/samsung,exynos-usi.h
> > @@ -0,0 +1,17 @@
> > +/* SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) */
> > +/*
> > + * Copyright (c) 2021 Linaro Ltd.
> > + * Author: Sam Protsenko <semen.protsenko@linaro.org>
> > + *
> > + * Device Tree bindings for Samsung Exynos USI (Universal Serial Interface).
> > + */
> > +
> > +#ifndef __DT_BINDINGS_SAMSUNG_EXYNOS_USI_H
> > +#define __DT_BINDINGS_SAMSUNG_EXYNOS_USI_H
> > +
> > +#define USI_V2_NONE          0
> > +#define USI_V2_UART          1
> > +#define USI_V2_SPI           2
> > +#define USI_V2_I2C           3
> > +
> > +#endif /* __DT_BINDINGS_SAMSUNG_EXYNOS_USI_H */
> > --
> > 2.30.2
> >
> >

On Fri, Dec 3, 2021 at 1:36 PM Sam Protsenko <semen.protsenko@linaro.org> wrote:
>
> On Tue, 30 Nov 2021 at 21:31, Rob Herring <robh@kernel.org> wrote:
> >
> > On Tue, Nov 30, 2021 at 01:13:21PM +0200, Sam Protsenko wrote:
> > > Add constants for choosing USIv2 configuration mode in device tree.
> > > Those are further used in USI driver to figure out which value to write
> > > into SW_CONF register. Also document USIv2 IP-core bindings.
> > >
> > > Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
> > > ---
> > > Changes in v2:
> > >   - Combined dt-bindings doc and dt-bindings header patches
> > >   - Added i2c node to example in bindings doc
> > >   - Added mentioning of shared internal circuits
> > >   - Added USI_V2_NONE value to bindings header
> > >
> > >  .../bindings/soc/samsung/exynos-usi.yaml      | 135 ++++++++++++++++++
> > >  include/dt-bindings/soc/samsung,exynos-usi.h  |  17 +++
> > >  2 files changed, 152 insertions(+)
> > >  create mode 100644 Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml
> > >  create mode 100644 include/dt-bindings/soc/samsung,exynos-usi.h
> > >
> > > diff --git a/Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml b/Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml
> > > new file mode 100644
> > > index 000000000000..a822bc62b3cd
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml
> > > @@ -0,0 +1,135 @@
> > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/soc/samsung/exynos-usi.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: Samsung's Exynos USI (Universal Serial Interface) binding
> > > +
> > > +maintainers:
> > > +  - Sam Protsenko <semen.protsenko@linaro.org>
> > > +  - Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
> > > +
> > > +description: |
> > > +  USI IP-core provides selectable serial protocol (UART, SPI or High-Speed I2C).
> > > +  USI shares almost all internal circuits within each protocol, so only one
> > > +  protocol can be chosen at a time. USI is modeled as a node with zero or more
> > > +  child nodes, each representing a serial sub-node device. The mode setting
> > > +  selects which particular function will be used.
> > > +
> > > +  Refer to next bindings documentation for information on protocol subnodes that
> > > +  can exist under USI node:
> > > +
> > > +  [1] Documentation/devicetree/bindings/serial/samsung_uart.yaml
> > > +  [2] Documentation/devicetree/bindings/i2c/i2c-exynos5.txt
> > > +  [3] Documentation/devicetree/bindings/spi/spi-samsung.txt
> > > +
> > > +properties:
> > > +  $nodename:
> > > +    pattern: "^usi@[0-9a-f]+$"
> > > +
> > > +  compatible:
> > > +    const: samsung,exynos-usi-v2
> >
> > Use SoC based compatibles.
> >
>
> In this particular case, I'd really prefer to have it like this. Most
> likely we'll only have USIv1 and USIv1 in the end, and I think that
> would be more clear to have USI version in compatible, rather than SoC
> name. Please let me know if you have a strong opinion on this one --
> if so I'll re-send.

Fine if you have some evidence the ratio of versions to SoC are much
more than 1:1 and the versions correspond to something (IOW, you
aren't making them up).

We went down the version # path with QCom and in the end about every
SoC had a different version.

>
> > > +
> > > +  reg:
> > > +    maxItems: 1
> > > +
> > > +  clocks:
> > > +    items:
> > > +      - description: Bus (APB) clock
> > > +      - description: Operating clock for UART/SPI/I2C protocol
> > > +
> > > +  clock-names:
> > > +    items:
> > > +      - const: pclk
> > > +      - const: ipclk
> > > +
> > > +  ranges: true
> > > +
> > > +  "#address-cells":
> > > +    const: 1
> > > +
> > > +  "#size-cells":
> > > +    const: 1
> > > +
> > > +  samsung,sysreg:
> > > +    $ref: /schemas/types.yaml#/definitions/phandle-array
> > > +    description:
> > > +      Should be phandle/offset pair. The phandle to System Register syscon node
> > > +      (for the same domain where this USI controller resides) and the offset
> > > +      of SW_CONF register for this USI controller.
> > > +
> > > +  samsung,mode:
> > > +    $ref: /schemas/types.yaml#/definitions/uint32
> > > +    description:
> > > +      Selects USI function (which serial protocol to use). Refer to
> > > +      <include/dt-bindings/soc/samsung,exynos-usi.h> for valid USI mode values.
> >
> > This seems to be redundant. Just check which child is enabled.
> >
>
> I think it's not that easy. Soon we'll have USIv1 support added, and
> that has some weird configurations, like having dual I2C mode (two
> child I2C nodes must be enabled) and UART+I2C mode, etc.

So you are going to turn around and make this an array? If you already
know you have changes, I'd rather review this all at once.

> Looks like it
> might take some not very elegant logic to figure out which exactly
> mode value should be written in SW_CONF register in that way, it's
> much easier to just specify mode in USI node. Also, that reflects
> hardware better: we actually write that specified mode to SW_CONF
> register.

You just have to compare the child node names or compatibles.

> Also, later we might want to be able to switch that mode via
> SysFS, e.g. for testing purposes. Current design seems to be better
> suited for some things like that.

The binding should have no impact on that. If for testing, use debugfs.

> Please let me know if you have a strong opinion on this one, or it's
> ok to leave it as is.
>
> All other comments are addressed and will be present in v3. Thanks for
> the review!

On Fri, 3 Dec 2021 at 22:40, Rob Herring <robh@kernel.org> wrote:
>
> On Fri, Dec 3, 2021 at 1:36 PM Sam Protsenko <semen.protsenko@linaro.org> wrote:
> >
> > On Tue, 30 Nov 2021 at 21:31, Rob Herring <robh@kernel.org> wrote:
> > >
> > > On Tue, Nov 30, 2021 at 01:13:21PM +0200, Sam Protsenko wrote:
> > > > Add constants for choosing USIv2 configuration mode in device tree.
> > > > Those are further used in USI driver to figure out which value to write
> > > > into SW_CONF register. Also document USIv2 IP-core bindings.
> > > >
> > > > Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
> > > > ---
> > > > Changes in v2:
> > > >   - Combined dt-bindings doc and dt-bindings header patches
> > > >   - Added i2c node to example in bindings doc
> > > >   - Added mentioning of shared internal circuits
> > > >   - Added USI_V2_NONE value to bindings header
> > > >
> > > >  .../bindings/soc/samsung/exynos-usi.yaml      | 135 ++++++++++++++++++
> > > >  include/dt-bindings/soc/samsung,exynos-usi.h  |  17 +++
> > > >  2 files changed, 152 insertions(+)
> > > >  create mode 100644 Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml
> > > >  create mode 100644 include/dt-bindings/soc/samsung,exynos-usi.h
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml b/Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml
> > > > new file mode 100644
> > > > index 000000000000..a822bc62b3cd
> > > > --- /dev/null
> > > > +++ b/Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml
> > > > @@ -0,0 +1,135 @@
> > > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > > +%YAML 1.2
> > > > +---
> > > > +$id: http://devicetree.org/schemas/soc/samsung/exynos-usi.yaml#
> > > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > > +
> > > > +title: Samsung's Exynos USI (Universal Serial Interface) binding
> > > > +
> > > > +maintainers:
> > > > +  - Sam Protsenko <semen.protsenko@linaro.org>
> > > > +  - Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
> > > > +
> > > > +description: |
> > > > +  USI IP-core provides selectable serial protocol (UART, SPI or High-Speed I2C).
> > > > +  USI shares almost all internal circuits within each protocol, so only one
> > > > +  protocol can be chosen at a time. USI is modeled as a node with zero or more
> > > > +  child nodes, each representing a serial sub-node device. The mode setting
> > > > +  selects which particular function will be used.
> > > > +
> > > > +  Refer to next bindings documentation for information on protocol subnodes that
> > > > +  can exist under USI node:
> > > > +
> > > > +  [1] Documentation/devicetree/bindings/serial/samsung_uart.yaml
> > > > +  [2] Documentation/devicetree/bindings/i2c/i2c-exynos5.txt
> > > > +  [3] Documentation/devicetree/bindings/spi/spi-samsung.txt
> > > > +
> > > > +properties:
> > > > +  $nodename:
> > > > +    pattern: "^usi@[0-9a-f]+$"
> > > > +
> > > > +  compatible:
> > > > +    const: samsung,exynos-usi-v2
> > >
> > > Use SoC based compatibles.
> > >
> >
> > In this particular case, I'd really prefer to have it like this. Most
> > likely we'll only have USIv1 and USIv1 in the end, and I think that
> > would be more clear to have USI version in compatible, rather than SoC
> > name. Please let me know if you have a strong opinion on this one --
> > if so I'll re-send.
>
> Fine if you have some evidence the ratio of versions to SoC are much
> more than 1:1 and the versions correspond to something (IOW, you
> aren't making them up).
>

Yes, it's documented in TRM for different SoCs (USI version 2), and
there are even dedicated registers where you can read the USI IP-core
version. Right now we only know about two USI versions: v1 and v2 (can
be found for example from different published Samsung downstream
kernels, and from TRMs). So the USI block is standardized and
versioned.

> We went down the version # path with QCom and in the end about every
> SoC had a different version.
>
> >
> > > > +
> > > > +  reg:
> > > > +    maxItems: 1
> > > > +
> > > > +  clocks:
> > > > +    items:
> > > > +      - description: Bus (APB) clock
> > > > +      - description: Operating clock for UART/SPI/I2C protocol
> > > > +
> > > > +  clock-names:
> > > > +    items:
> > > > +      - const: pclk
> > > > +      - const: ipclk
> > > > +
> > > > +  ranges: true
> > > > +
> > > > +  "#address-cells":
> > > > +    const: 1
> > > > +
> > > > +  "#size-cells":
> > > > +    const: 1
> > > > +
> > > > +  samsung,sysreg:
> > > > +    $ref: /schemas/types.yaml#/definitions/phandle-array
> > > > +    description:
> > > > +      Should be phandle/offset pair. The phandle to System Register syscon node
> > > > +      (for the same domain where this USI controller resides) and the offset
> > > > +      of SW_CONF register for this USI controller.
> > > > +
> > > > +  samsung,mode:
> > > > +    $ref: /schemas/types.yaml#/definitions/uint32
> > > > +    description:
> > > > +      Selects USI function (which serial protocol to use). Refer to
> > > > +      <include/dt-bindings/soc/samsung,exynos-usi.h> for valid USI mode values.
> > >
> > > This seems to be redundant. Just check which child is enabled.
> > >
> >
> > I think it's not that easy. Soon we'll have USIv1 support added, and
> > that has some weird configurations, like having dual I2C mode (two
> > child I2C nodes must be enabled) and UART+I2C mode, etc.
>
> So you are going to turn around and make this an array? If you already
> know you have changes, I'd rather review this all at once.
>

No, I'd imagine that would be just a bunch of new dt-bindings
constants, for USI_V1. For example, for USI_V2 you already can see
these:

    #define USI_V2_NONE        0
    #define USI_V2_UART        1
    #define USI_V2_SPI        2
    #define USI_V2_I2C        3

and for USI_V1 it would probably be something like this, judging from [1]:

    #define USI_V1_NONE        4
    #define USI_V1_I2C0  5
    #define USI_V1_I2C1  6
    #define USI_V1_I2C0_I2C1_DUAL  7
    #define USI_V1_SPI  8
    #define USI_V1_UART  9
    #define USI_V1_UART_I2C1_DUAL  10

Guess in that case parsing enabled nodes and figuring out which mode
we have, and which value should be written into SW_CONF -- might be
not trivial. Having explicit "mode" property simplifies things.

[1] https://github.com/ibanezbass/universal7885/blob/oneui/drivers/soc/samsung/usi.c

> > Looks like it
> > might take some not very elegant logic to figure out which exactly
> > mode value should be written in SW_CONF register in that way, it's
> > much easier to just specify mode in USI node. Also, that reflects
> > hardware better: we actually write that specified mode to SW_CONF
> > register.
>
> You just have to compare the child node names or compatibles.
>

For USIv1 that would allow for some invalid combinations (e.g.
UART+I2C1 is possible, but SPI+I2C1 can't be configured). Also, the
list of supported compatibles might grow in future, which will have us
constantly add the list to the driver. And node names might be not
valid (e.g. you can see @hsi2c names are used in some dts's instead of
@i2c; also downstream kernels might have all kinds of names -- not a
strong point, but still).

Anyway, it can be implemented, and maybe I'm a bit biased here; so if
I still didn't convince you that benefits of having "mode" property
outweigh the disadvantages, please let me know -- I can send it in
next submission.

> > Also, later we might want to be able to switch that mode via
> > SysFS, e.g. for testing purposes. Current design seems to be better
> > suited for some things like that.
>
> The binding should have no impact on that. If for testing, use debugfs.
>
> > Please let me know if you have a strong opinion on this one, or it's
> > ok to leave it as is.
> >
> > All other comments are addressed and will be present in v3. Thanks for
> > the review!

On 03/12/2021 21:40, Rob Herring wrote:
> On Fri, Dec 3, 2021 at 1:36 PM Sam Protsenko <semen.protsenko@linaro.org> wrote:
>>
>> On Tue, 30 Nov 2021 at 21:31, Rob Herring <robh@kernel.org> wrote:
>>>
>>> On Tue, Nov 30, 2021 at 01:13:21PM +0200, Sam Protsenko wrote:
>>>> Add constants for choosing USIv2 configuration mode in device tree.
>>>> Those are further used in USI driver to figure out which value to write
>>>> into SW_CONF register. Also document USIv2 IP-core bindings.
>>>>
>>>> Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
>>>> ---
>>>> Changes in v2:
>>>>   - Combined dt-bindings doc and dt-bindings header patches
>>>>   - Added i2c node to example in bindings doc
>>>>   - Added mentioning of shared internal circuits
>>>>   - Added USI_V2_NONE value to bindings header
>>>>
>>>>  .../bindings/soc/samsung/exynos-usi.yaml      | 135 ++++++++++++++++++
>>>>  include/dt-bindings/soc/samsung,exynos-usi.h  |  17 +++
>>>>  2 files changed, 152 insertions(+)
>>>>  create mode 100644 Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml
>>>>  create mode 100644 include/dt-bindings/soc/samsung,exynos-usi.h
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml b/Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml
>>>> new file mode 100644
>>>> index 000000000000..a822bc62b3cd
>>>> --- /dev/null
>>>> +++ b/Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml
>>>> @@ -0,0 +1,135 @@
>>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>>> +%YAML 1.2
>>>> +---
>>>> +$id: http://devicetree.org/schemas/soc/samsung/exynos-usi.yaml#
>>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>>> +
>>>> +title: Samsung's Exynos USI (Universal Serial Interface) binding
>>>> +
>>>> +maintainers:
>>>> +  - Sam Protsenko <semen.protsenko@linaro.org>
>>>> +  - Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
>>>> +
>>>> +description: |
>>>> +  USI IP-core provides selectable serial protocol (UART, SPI or High-Speed I2C).
>>>> +  USI shares almost all internal circuits within each protocol, so only one
>>>> +  protocol can be chosen at a time. USI is modeled as a node with zero or more
>>>> +  child nodes, each representing a serial sub-node device. The mode setting
>>>> +  selects which particular function will be used.
>>>> +
>>>> +  Refer to next bindings documentation for information on protocol subnodes that
>>>> +  can exist under USI node:
>>>> +
>>>> +  [1] Documentation/devicetree/bindings/serial/samsung_uart.yaml
>>>> +  [2] Documentation/devicetree/bindings/i2c/i2c-exynos5.txt
>>>> +  [3] Documentation/devicetree/bindings/spi/spi-samsung.txt
>>>> +
>>>> +properties:
>>>> +  $nodename:
>>>> +    pattern: "^usi@[0-9a-f]+$"
>>>> +
>>>> +  compatible:
>>>> +    const: samsung,exynos-usi-v2
>>>
>>> Use SoC based compatibles.
>>>
>>
>> In this particular case, I'd really prefer to have it like this. Most
>> likely we'll only have USIv1 and USIv1 in the end, and I think that
>> would be more clear to have USI version in compatible, rather than SoC
>> name. Please let me know if you have a strong opinion on this one --
>> if so I'll re-send.
> 
> Fine if you have some evidence the ratio of versions to SoC are much
> more than 1:1 and the versions correspond to something (IOW, you
> aren't making them up).
> 
> We went down the version # path with QCom and in the end about every
> SoC had a different version.

I am against v1/v2 versions. The documentation in Samsung was always
poor in that matter. There were mistakes or confusions so it wasn't
always obvious which IP-block version comes with which SoC. Not
mentioning that several contributors do not have access to Samsung
datasheets and they submit code based on GPL compliance packages, so
they won't know which version they have for given SoC.

OTOH there is no single benefit of using USI v1/v2, except "liking".

Best regards,
Krzysztof

On 04/12/2021 01:18, Sam Protsenko wrote:
> On Fri, 3 Dec 2021 at 22:40, Rob Herring <robh@kernel.org> wrote:
>>
>> On Fri, Dec 3, 2021 at 1:36 PM Sam Protsenko <semen.protsenko@linaro.org> wrote:
>>>
>>> On Tue, 30 Nov 2021 at 21:31, Rob Herring <robh@kernel.org> wrote:
>>>>
>>>> On Tue, Nov 30, 2021 at 01:13:21PM +0200, Sam Protsenko wrote:
>>>>> Add constants for choosing USIv2 configuration mode in device tree.
>>>>> Those are further used in USI driver to figure out which value to write
>>>>> into SW_CONF register. Also document USIv2 IP-core bindings.
>>>>>
>>>>> Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
>>>>> ---
>>>>> Changes in v2:
>>>>>   - Combined dt-bindings doc and dt-bindings header patches
>>>>>   - Added i2c node to example in bindings doc
>>>>>   - Added mentioning of shared internal circuits
>>>>>   - Added USI_V2_NONE value to bindings header
>>>>>
>>>>>  .../bindings/soc/samsung/exynos-usi.yaml      | 135 ++++++++++++++++++
>>>>>  include/dt-bindings/soc/samsung,exynos-usi.h  |  17 +++
>>>>>  2 files changed, 152 insertions(+)
>>>>>  create mode 100644 Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml
>>>>>  create mode 100644 include/dt-bindings/soc/samsung,exynos-usi.h
>>>>>
>>>>> diff --git a/Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml b/Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml
>>>>> new file mode 100644
>>>>> index 000000000000..a822bc62b3cd
>>>>> --- /dev/null
>>>>> +++ b/Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml
>>>>> @@ -0,0 +1,135 @@
>>>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>>>> +%YAML 1.2
>>>>> +---
>>>>> +$id: http://devicetree.org/schemas/soc/samsung/exynos-usi.yaml#
>>>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>>>> +
>>>>> +title: Samsung's Exynos USI (Universal Serial Interface) binding
>>>>> +
>>>>> +maintainers:
>>>>> +  - Sam Protsenko <semen.protsenko@linaro.org>
>>>>> +  - Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
>>>>> +
>>>>> +description: |
>>>>> +  USI IP-core provides selectable serial protocol (UART, SPI or High-Speed I2C).
>>>>> +  USI shares almost all internal circuits within each protocol, so only one
>>>>> +  protocol can be chosen at a time. USI is modeled as a node with zero or more
>>>>> +  child nodes, each representing a serial sub-node device. The mode setting
>>>>> +  selects which particular function will be used.
>>>>> +
>>>>> +  Refer to next bindings documentation for information on protocol subnodes that
>>>>> +  can exist under USI node:
>>>>> +
>>>>> +  [1] Documentation/devicetree/bindings/serial/samsung_uart.yaml
>>>>> +  [2] Documentation/devicetree/bindings/i2c/i2c-exynos5.txt
>>>>> +  [3] Documentation/devicetree/bindings/spi/spi-samsung.txt
>>>>> +
>>>>> +properties:
>>>>> +  $nodename:
>>>>> +    pattern: "^usi@[0-9a-f]+$"
>>>>> +
>>>>> +  compatible:
>>>>> +    const: samsung,exynos-usi-v2
>>>>
>>>> Use SoC based compatibles.
>>>>
>>>
>>> In this particular case, I'd really prefer to have it like this. Most
>>> likely we'll only have USIv1 and USIv1 in the end, and I think that
>>> would be more clear to have USI version in compatible, rather than SoC
>>> name. Please let me know if you have a strong opinion on this one --
>>> if so I'll re-send.
>>
>> Fine if you have some evidence the ratio of versions to SoC are much
>> more than 1:1 and the versions correspond to something (IOW, you
>> aren't making them up).
>>
> 
> Yes, it's documented in TRM for different SoCs (USI version 2), and
> there are even dedicated registers where you can read the USI IP-core
> version. Right now we only know about two USI versions: v1 and v2 (can
> be found for example from different published Samsung downstream
> kernels, and from TRMs). So the USI block is standardized and
> versioned.

There is no version register for USIv1 and it does not look at all as
standardized. At least not documented. Just because later Samsung
introduced some logic behind it, it's not a proof it is standardized.
It's not. Standard comes with specification and there is no such.
Description of current implementation is not a specification.

Best regards,
Krzysztof

On Sat, 4 Dec 2021 at 13:28, Krzysztof Kozlowski
<krzysztof.kozlowski@canonical.com> wrote:
>
> On 03/12/2021 21:40, Rob Herring wrote:
> > On Fri, Dec 3, 2021 at 1:36 PM Sam Protsenko <semen.protsenko@linaro.org> wrote:
> >>
> >> On Tue, 30 Nov 2021 at 21:31, Rob Herring <robh@kernel.org> wrote:
> >>>
> >>> On Tue, Nov 30, 2021 at 01:13:21PM +0200, Sam Protsenko wrote:
> >>>> Add constants for choosing USIv2 configuration mode in device tree.
> >>>> Those are further used in USI driver to figure out which value to write
> >>>> into SW_CONF register. Also document USIv2 IP-core bindings.
> >>>>
> >>>> Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
> >>>> ---
> >>>> Changes in v2:
> >>>>   - Combined dt-bindings doc and dt-bindings header patches
> >>>>   - Added i2c node to example in bindings doc
> >>>>   - Added mentioning of shared internal circuits
> >>>>   - Added USI_V2_NONE value to bindings header
> >>>>
> >>>>  .../bindings/soc/samsung/exynos-usi.yaml      | 135 ++++++++++++++++++
> >>>>  include/dt-bindings/soc/samsung,exynos-usi.h  |  17 +++
> >>>>  2 files changed, 152 insertions(+)
> >>>>  create mode 100644 Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml
> >>>>  create mode 100644 include/dt-bindings/soc/samsung,exynos-usi.h
> >>>>
> >>>> diff --git a/Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml b/Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml
> >>>> new file mode 100644
> >>>> index 000000000000..a822bc62b3cd
> >>>> --- /dev/null
> >>>> +++ b/Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml
> >>>> @@ -0,0 +1,135 @@
> >>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> >>>> +%YAML 1.2
> >>>> +---
> >>>> +$id: http://devicetree.org/schemas/soc/samsung/exynos-usi.yaml#
> >>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> >>>> +
> >>>> +title: Samsung's Exynos USI (Universal Serial Interface) binding
> >>>> +
> >>>> +maintainers:
> >>>> +  - Sam Protsenko <semen.protsenko@linaro.org>
> >>>> +  - Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
> >>>> +
> >>>> +description: |
> >>>> +  USI IP-core provides selectable serial protocol (UART, SPI or High-Speed I2C).
> >>>> +  USI shares almost all internal circuits within each protocol, so only one
> >>>> +  protocol can be chosen at a time. USI is modeled as a node with zero or more
> >>>> +  child nodes, each representing a serial sub-node device. The mode setting
> >>>> +  selects which particular function will be used.
> >>>> +
> >>>> +  Refer to next bindings documentation for information on protocol subnodes that
> >>>> +  can exist under USI node:
> >>>> +
> >>>> +  [1] Documentation/devicetree/bindings/serial/samsung_uart.yaml
> >>>> +  [2] Documentation/devicetree/bindings/i2c/i2c-exynos5.txt
> >>>> +  [3] Documentation/devicetree/bindings/spi/spi-samsung.txt
> >>>> +
> >>>> +properties:
> >>>> +  $nodename:
> >>>> +    pattern: "^usi@[0-9a-f]+$"
> >>>> +
> >>>> +  compatible:
> >>>> +    const: samsung,exynos-usi-v2
> >>>
> >>> Use SoC based compatibles.
> >>>
> >>
> >> In this particular case, I'd really prefer to have it like this. Most
> >> likely we'll only have USIv1 and USIv1 in the end, and I think that
> >> would be more clear to have USI version in compatible, rather than SoC
> >> name. Please let me know if you have a strong opinion on this one --
> >> if so I'll re-send.
> >
> > Fine if you have some evidence the ratio of versions to SoC are much
> > more than 1:1 and the versions correspond to something (IOW, you
> > aren't making them up).
> >
> > We went down the version # path with QCom and in the end about every
> > SoC had a different version.
>
> I am against v1/v2 versions. The documentation in Samsung was always
> poor in that matter. There were mistakes or confusions so it wasn't
> always obvious which IP-block version comes with which SoC. Not
> mentioning that several contributors do not have access to Samsung
> datasheets and they submit code based on GPL compliance packages, so
> they won't know which version they have for given SoC.
>
> OTOH there is no single benefit of using USI v1/v2, except "liking".
>

Ok, I'll do as you ask. In general I agree, but I still think in this
particular case using "usi" in compatible is feasible. Anyway, I have
no strong opinion on this one, and it's easy to rework.

> Best regards,
> Krzysztof