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[v2,0/4] reset: gpio: ASoC: shared GPIO resets

Message ID 20240105155918.279657-1-krzysztof.kozlowski@linaro.org
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Series reset: gpio: ASoC: shared GPIO resets | expand

Message

Krzysztof Kozlowski Jan. 5, 2024, 3:59 p.m. UTC 
Hi,

Changes in v2
=============
1. wsa884x.c: add missing return in wsa884x_get_reset(), correct comment.
2. qcom,wsa8840.yaml: fix oneOf syntax.
3. reset/core.c:
   - Revise approach based on Bartosz comments: parse the reset-gpios phandle
     with arguments, do not use deprecated API and do not rely on gpio_desc
     pointer.
   - Create a list of instantiated platform devices to avoid any duplicates.
   - After creating reset-gpio platform device, try to get new reset controller
     or return EPROBE_DEFER.
   - Drop the "cookie" member and add new "of_args" to "struct
     reset_controller_dev".
4. reset-gpio.c:
   - Fix smatch warning on platdata evaluation.
   - Parse GPIO args and store them in rc.of_args.

Description
===========

We have at least few cases where hardware engineers decided to use one
powerdown/shutdown/reset GPIO line for multiple devices:

1. WSA884x (this and previous patch):
https://lore.kernel.org/all/b7aeda24-d638-45b7-8e30-80d287f498f8@sirena.org.uk/
2. https://lore.kernel.org/all/20231027033104.1348921-1-chris.packham@alliedtelesis.co.nz/
3. https://lore.kernel.org/lkml/20191030120440.3699-1-peter.ujfalusi@ti.com/
4. https://lore.kernel.org/all/20211018234923.1769028-1-sean.anderson@seco.com/
5. https://social.treehouse.systems/@marcan/111268780311634160

I try to solve my case, hopefuly Chris' (2), partially Sean's (4) and maybe
Hectors (5), using Rob's suggestion:

https://lore.kernel.org/all/YXi5CUCEi7YmNxXM@robh.at.kernel.org/

Best regards,
Krzysztof

Cc: Chris Packham <chris.packham@alliedtelesis.co.nz>
Cc: Bartosz Golaszewski <brgl@bgdev.pl>
Cc: Sean Anderson <sean.anderson@seco.com>

Krzysztof Kozlowski (4):
  reset: gpio: Add GPIO-based reset controller
  reset: Instantiate reset GPIO controller for shared reset-gpios
  ASoC: dt-bindings: qcom,wsa8840: Add reset-gpios for shared line
  ASoC: codecs: wsa884x: Allow sharing reset GPIO

 .../bindings/sound/qcom,wsa8840.yaml          |  11 +-
 MAINTAINERS                                   |   5 +
 drivers/reset/Kconfig                         |   9 +
 drivers/reset/Makefile                        |   1 +
 drivers/reset/core.c                          | 176 ++++++++++++++++--
 drivers/reset/reset-gpio.c                    | 121 ++++++++++++
 include/linux/reset-controller.h              |   4 +
 sound/soc/codecs/wsa884x.c                    |  53 +++++-
 8 files changed, 356 insertions(+), 24 deletions(-)
 create mode 100644 drivers/reset/reset-gpio.c

Comments

Krzysztof Kozlowski Jan. 6, 2024, 3:28 p.m. UTC | #1 
On 05/01/2024 17:39, Biju Das wrote:
> Hi Krzysztof Kozlowski,
> 
> Thanks for the patch.
> 
>> -----Original Message-----
>> From: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
>> Sent: Friday, January 5, 2024 3:59 PM
>> Subject: [PATCH v2 1/4] reset: gpio: Add GPIO-based reset controller
>>
>> Add a simple driver to control GPIO-based resets using the reset
>> controller API for the cases when the GPIOs are shared and reset should be
>> coordinated.  The driver is expected to be used by reset core framework
>> for ad-hoc reset controllers.
>>
>> Cc: Bartosz Golaszewski <brgl@bgdev.pl>
>> Cc: Sean Anderson <sean.anderson@seco.com>
>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
>> ---
>>  MAINTAINERS                |   5 ++
>>  drivers/reset/Kconfig      |   9 +++
>>  drivers/reset/Makefile     |   1 +
>>  drivers/reset/reset-gpio.c | 121 +++++++++++++++++++++++++++++++++++++
>>  4 files changed, 136 insertions(+)
>>  create mode 100644 drivers/reset/reset-gpio.c
>>
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index 7fe27cd60e1b..a0fbd4814bc7 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -8866,6 +8866,11 @@ F:	Documentation/i2c/muxes/i2c-mux-gpio.rst
>>  F:	drivers/i2c/muxes/i2c-mux-gpio.c
>>  F:	include/linux/platform_data/i2c-mux-gpio.h
>>
>> +GENERIC GPIO RESET DRIVER
>> +M:	Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
>> +S:	Maintained
>> +F:	drivers/reset/reset-gpio.c
>> +
>>  GENERIC HDLC (WAN) DRIVERS
>>  M:	Krzysztof Halasa <khc@pm.waw.pl>
>>  S:	Maintained
>> diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig index
>> ccd59ddd7610..bb1b5a326eb7 100644
>> --- a/drivers/reset/Kconfig
>> +++ b/drivers/reset/Kconfig
>> @@ -66,6 +66,15 @@ config RESET_BRCMSTB_RESCAL
>>  	  This enables the RESCAL reset controller for SATA, PCIe0, or PCIe1
>> on
>>  	  BCM7216.
>>
>> +config RESET_GPIO
>> +	tristate "GPIO reset controller"
>> +	help
>> +	  This enables a generic reset controller for resets attached via
>> +	  GPIOs.  Typically for OF platforms this driver expects "reset-
>> gpios"
>> +	  property.
>> +
>> +	  If compiled as module, it will be called reset-gpio.
>> +
>>  config RESET_HSDK
>>  	bool "Synopsys HSDK Reset Driver"
>>  	depends on HAS_IOMEM
>> diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile index
>> 8270da8a4baa..fd8b49fa46fc 100644
>> --- a/drivers/reset/Makefile
>> +++ b/drivers/reset/Makefile
>> @@ -11,6 +11,7 @@ obj-$(CONFIG_RESET_BCM6345) += reset-bcm6345.o
>>  obj-$(CONFIG_RESET_BERLIN) += reset-berlin.o
>>  obj-$(CONFIG_RESET_BRCMSTB) += reset-brcmstb.o
>>  obj-$(CONFIG_RESET_BRCMSTB_RESCAL) += reset-brcmstb-rescal.o
>> +obj-$(CONFIG_RESET_GPIO) += reset-gpio.o
>>  obj-$(CONFIG_RESET_HSDK) += reset-hsdk.o
>>  obj-$(CONFIG_RESET_IMX7) += reset-imx7.o
>>  obj-$(CONFIG_RESET_INTEL_GW) += reset-intel-gw.o diff --git
>> a/drivers/reset/reset-gpio.c b/drivers/reset/reset-gpio.c new file mode
>> 100644 index 000000000000..cf0a867cbc5f
>> --- /dev/null
>> +++ b/drivers/reset/reset-gpio.c
>> @@ -0,0 +1,121 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +
>> +#include <linux/gpio/consumer.h>
>> +#include <linux/mod_devicetable.h>
>> +#include <linux/module.h>
>> +#include <linux/of.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/reset-controller.h>
>> +
>> +struct reset_gpio_priv {
>> +	struct reset_controller_dev rc;
>> +	struct gpio_desc *reset;
>> +};
>> +
>> +static inline struct reset_gpio_priv
>> +*rc_to_reset_gpio(struct reset_controller_dev *rc) {
>> +	return container_of(rc, struct reset_gpio_priv, rc); }
>> +
>> +static int reset_gpio_assert(struct reset_controller_dev *rc, unsigned
>> +long id) {
>> +	struct reset_gpio_priv *priv = rc_to_reset_gpio(rc);
>> +
>> +	gpiod_set_value_cansleep(priv->reset, 1);
>> +
>> +	return 0;
>> +}
>> +
>> +static int reset_gpio_deassert(struct reset_controller_dev *rc,
>> +			       unsigned long id)
>> +{
>> +	struct reset_gpio_priv *priv = rc_to_reset_gpio(rc);
>> +
>> +	gpiod_set_value_cansleep(priv->reset, 0);
>> +
>> +	return 0;
>> +}
>> +
>> +static int reset_gpio_status(struct reset_controller_dev *rc, unsigned
>> +long id) {
>> +	struct reset_gpio_priv *priv = rc_to_reset_gpio(rc);
>> +
>> +	return gpiod_get_value_cansleep(priv->reset);
>> +}
>> +
>> +static const struct reset_control_ops reset_gpio_ops = {
>> +	.assert = reset_gpio_assert,
>> +	.deassert = reset_gpio_deassert,
>> +	.status = reset_gpio_status,
>> +};
>> +
>> +static void reset_gpio_of_args_put(void *data) {
>> +	of_node_put(data);
>> +}
>> +
>> +static int reset_gpio_probe(struct platform_device *pdev) {
>> +	struct device *dev = &pdev->dev;
>> +	struct device_node **platdata = dev_get_platdata(dev);
>> +	struct of_phandle_args gpio_args;
>> +	struct reset_gpio_priv *priv;
>> +	int ret;
>> +
>> +	if (!platdata || !*platdata)
> 
> Maybe, if (!(platdata && *platdata)) which reduces 1 inversion operation.

I would not call it easier to understand... To me !A and !*A are quite
obvious and easy to read instantly because !A is obvious: check if it is
not NULL. Therefore original check is obvious: is NULL or points to
NULL? Then exit.

Now your check is a bit more complicated. It is not even frequent code
pattern which my brain used to see. You want to check if both are not
NULL and then negate it, wait, no, opposite, check if they are something
and then negate? To me it is really opposite of readable code.

Best regards,
Krzysztof
Biju Das Jan. 7, 2024, 10:46 a.m. UTC | #2 
Hi Krzysztof Kozlowski,

> -----Original Message-----
> From: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
> Sent: Saturday, January 6, 2024 3:29 PM
> Subject: Re: [PATCH v2 1/4] reset: gpio: Add GPIO-based reset controller
> 
> On 05/01/2024 17:39, Biju Das wrote:
> > Hi Krzysztof Kozlowski,
> >
> > Thanks for the patch.
> >
> >> -----Original Message-----
> >> From: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
> >> Sent: Friday, January 5, 2024 3:59 PM
> >> Subject: [PATCH v2 1/4] reset: gpio: Add GPIO-based reset controller
> >>
> >> Add a simple driver to control GPIO-based resets using the reset
> >> controller API for the cases when the GPIOs are shared and reset
> >> should be coordinated.  The driver is expected to be used by reset
> >> core framework for ad-hoc reset controllers.
> >>
> >> Cc: Bartosz Golaszewski <brgl@bgdev.pl>
> >> Cc: Sean Anderson <sean.anderson@seco.com>
> >> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
> >> ---
> >>  MAINTAINERS                |   5 ++
> >>  drivers/reset/Kconfig      |   9 +++
> >>  drivers/reset/Makefile     |   1 +
> >>  drivers/reset/reset-gpio.c | 121
> >> +++++++++++++++++++++++++++++++++++++
> >>  4 files changed, 136 insertions(+)
> >>  create mode 100644 drivers/reset/reset-gpio.c
> >>
> >> diff --git a/MAINTAINERS b/MAINTAINERS index
> >> 7fe27cd60e1b..a0fbd4814bc7 100644
> >> --- a/MAINTAINERS
> >> +++ b/MAINTAINERS
> >> @@ -8866,6 +8866,11 @@ F:	Documentation/i2c/muxes/i2c-mux-gpio.rst
> >>  F:	drivers/i2c/muxes/i2c-mux-gpio.c
> >>  F:	include/linux/platform_data/i2c-mux-gpio.h
> >>
> >> +GENERIC GPIO RESET DRIVER
> >> +M:	Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
> >> +S:	Maintained
> >> +F:	drivers/reset/reset-gpio.c
> >> +
> >>  GENERIC HDLC (WAN) DRIVERS
> >>  M:	Krzysztof Halasa <khc@pm.waw.pl>
> >>  S:	Maintained
> >> diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig index
> >> ccd59ddd7610..bb1b5a326eb7 100644
> >> --- a/drivers/reset/Kconfig
> >> +++ b/drivers/reset/Kconfig
> >> @@ -66,6 +66,15 @@ config RESET_BRCMSTB_RESCAL
> >>  	  This enables the RESCAL reset controller for SATA, PCIe0, or
> >> PCIe1 on
> >>  	  BCM7216.
> >>
> >> +config RESET_GPIO
> >> +	tristate "GPIO reset controller"
> >> +	help
> >> +	  This enables a generic reset controller for resets attached via
> >> +	  GPIOs.  Typically for OF platforms this driver expects "reset-
> >> gpios"
> >> +	  property.
> >> +
> >> +	  If compiled as module, it will be called reset-gpio.
> >> +
> >>  config RESET_HSDK
> >>  	bool "Synopsys HSDK Reset Driver"
> >>  	depends on HAS_IOMEM
> >> diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile index
> >> 8270da8a4baa..fd8b49fa46fc 100644
> >> --- a/drivers/reset/Makefile
> >> +++ b/drivers/reset/Makefile
> >> @@ -11,6 +11,7 @@ obj-$(CONFIG_RESET_BCM6345) += reset-bcm6345.o
> >>  obj-$(CONFIG_RESET_BERLIN) += reset-berlin.o
> >>  obj-$(CONFIG_RESET_BRCMSTB) += reset-brcmstb.o
> >>  obj-$(CONFIG_RESET_BRCMSTB_RESCAL) += reset-brcmstb-rescal.o
> >> +obj-$(CONFIG_RESET_GPIO) += reset-gpio.o
> >>  obj-$(CONFIG_RESET_HSDK) += reset-hsdk.o
> >>  obj-$(CONFIG_RESET_IMX7) += reset-imx7.o
> >>  obj-$(CONFIG_RESET_INTEL_GW) += reset-intel-gw.o diff --git
> >> a/drivers/reset/reset-gpio.c b/drivers/reset/reset-gpio.c new file
> >> mode
> >> 100644 index 000000000000..cf0a867cbc5f
> >> --- /dev/null
> >> +++ b/drivers/reset/reset-gpio.c
> >> @@ -0,0 +1,121 @@
> >> +// SPDX-License-Identifier: GPL-2.0
> >> +
> >> +#include <linux/gpio/consumer.h>
> >> +#include <linux/mod_devicetable.h>
> >> +#include <linux/module.h>
> >> +#include <linux/of.h>
> >> +#include <linux/platform_device.h>
> >> +#include <linux/reset-controller.h>
> >> +
> >> +struct reset_gpio_priv {
> >> +	struct reset_controller_dev rc;
> >> +	struct gpio_desc *reset;
> >> +};
> >> +
> >> +static inline struct reset_gpio_priv *rc_to_reset_gpio(struct
> >> +reset_controller_dev *rc) {
> >> +	return container_of(rc, struct reset_gpio_priv, rc); }
> >> +
> >> +static int reset_gpio_assert(struct reset_controller_dev *rc,
> >> +unsigned long id) {
> >> +	struct reset_gpio_priv *priv = rc_to_reset_gpio(rc);
> >> +
> >> +	gpiod_set_value_cansleep(priv->reset, 1);
> >> +
> >> +	return 0;
> >> +}
> >> +
> >> +static int reset_gpio_deassert(struct reset_controller_dev *rc,
> >> +			       unsigned long id)
> >> +{
> >> +	struct reset_gpio_priv *priv = rc_to_reset_gpio(rc);
> >> +
> >> +	gpiod_set_value_cansleep(priv->reset, 0);
> >> +
> >> +	return 0;
> >> +}
> >> +
> >> +static int reset_gpio_status(struct reset_controller_dev *rc,
> >> +unsigned long id) {
> >> +	struct reset_gpio_priv *priv = rc_to_reset_gpio(rc);
> >> +
> >> +	return gpiod_get_value_cansleep(priv->reset);
> >> +}
> >> +
> >> +static const struct reset_control_ops reset_gpio_ops = {
> >> +	.assert = reset_gpio_assert,
> >> +	.deassert = reset_gpio_deassert,
> >> +	.status = reset_gpio_status,
> >> +};
> >> +
> >> +static void reset_gpio_of_args_put(void *data) {
> >> +	of_node_put(data);
> >> +}
> >> +
> >> +static int reset_gpio_probe(struct platform_device *pdev) {
> >> +	struct device *dev = &pdev->dev;
> >> +	struct device_node **platdata = dev_get_platdata(dev);
> >> +	struct of_phandle_args gpio_args;
> >> +	struct reset_gpio_priv *priv;
> >> +	int ret;
> >> +
> >> +	if (!platdata || !*platdata)
> >
> > Maybe, if (!(platdata && *platdata)) which reduces 1 inversion
> operation.
> 
> I would not call it easier to understand... To me !A and !*A are quite
> obvious and easy to read instantly because !A is obvious: check if it is
> not NULL. Therefore original check is obvious: is NULL or points to NULL?
> Then exit.
> 
> Now your check is a bit more complicated. It is not even frequent code
> pattern which my brain used to see. You want to check if both are not NULL
> and then negate it, wait, no, opposite, check if they are something and
> then negate? To me it is really opposite of readable code.

I agree maybe it is not readable, even though it reduces 1 extra operation.

!(Valid pointer AND points to a non NULL value)
Then exit.

Cheers,
Biju
Krzysztof Kozlowski Jan. 7, 2024, 11:56 a.m. UTC | #3 
On 07/01/2024 11:46, Biju Das wrote:
>>>> +
>>>> +	if (!platdata || !*platdata)
>>>
>>> Maybe, if (!(platdata && *platdata)) which reduces 1 inversion
>> operation.
>>
>> I would not call it easier to understand... To me !A and !*A are quite
>> obvious and easy to read instantly because !A is obvious: check if it is
>> not NULL. Therefore original check is obvious: is NULL or points to NULL?
>> Then exit.
>>
>> Now your check is a bit more complicated. It is not even frequent code
>> pattern which my brain used to see. You want to check if both are not NULL
>> and then negate it, wait, no, opposite, check if they are something and
>> then negate? To me it is really opposite of readable code.
> 
> I agree maybe it is not readable, even though it reduces 1 extra operation.
> 

Number of operations does not matter. Code readability matters.
Compilers are nowadays smarter than us, so don't write code more
difficult to read just to optimize some instruction like this.

Best regards,
Krzysztof
Krzysztof Kozlowski Jan. 8, 2024, 9:44 a.m. UTC | #4 
On 07/01/2024 22:35, Chris Packham wrote:
> Hi Krzysztof,
> 
> On 6/01/24 04:59, Krzysztof Kozlowski wrote:
> 
> Hi,

You quoting got broken.

> 
> 
> 
> I'll try and take these for a spin on my hardware. I think I'll need to update the pca954x mux driver along similar lines to your changes to the wsa884x. Do you happen to have an example of what the reset-controller usage looks like in a devicetree? I can probably figure it out based on the code but I figured I'd ask just in case you already had an example handy.

Just add "reset-gpios" property in the device node, not the bus.

Best regards,
Krzysztof