[1/3] arm64: dts: qcom: sdm630: fix UART1 pin bias

There is no "bias-no-pull" property.  Assume intentions were disabling
bias.

Fixes: b190fb010664 ("arm64: dts: qcom: sdm630: Add sdm630 dts file")
Cc: <stable@vger.kernel.org>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

---

Not tested on hardware.
---
 arch/arm64/boot/dts/qcom/sdm630.dtsi | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Hi,

On Fri, Sep 30, 2022 at 11:22 AM Krzysztof Kozlowski
<krzysztof.kozlowski@linaro.org> wrote:
>
> The pin configuration (done with generic pin controller helpers and
> as expressed by bindings) requires children nodes with either:
> 1. "pins" property and the actual configuration,
> 2. another set of nodes with above point.
>
> The qup_spi2_default pin configuration used second method - with a
> "pinmux" child.
>
> Fixes: 8d23a0040475 ("arm64: dts: qcom: db845c: add Low speed expansion i2c and spi nodes")
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
>
> ---
>
> Not tested on hardware.
> ---
>  arch/arm64/boot/dts/qcom/sdm845-db845c.dts | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/boot/dts/qcom/sdm845-db845c.dts b/arch/arm64/boot/dts/qcom/sdm845-db845c.dts
> index 132417e2d11e..a157eab66dee 100644
> --- a/arch/arm64/boot/dts/qcom/sdm845-db845c.dts
> +++ b/arch/arm64/boot/dts/qcom/sdm845-db845c.dts
> @@ -1123,7 +1123,9 @@ &wifi {
>
>  /* PINCTRL - additions to nodes defined in sdm845.dtsi */
>  &qup_spi2_default {
> -       drive-strength = <16>;
> +       pinmux {
> +               drive-strength = <16>;
> +       };

The convention on Qualcomm boards of this era is that muxing (setting
the function) is done under a "pinmux" node and, unless some of the
pins need to be treated differently like for the UARTs, configuration
(bias, drive strength, etc) is done under a "pinconf" subnode. I
believe that the "pinconf" subnode also needs to replicate the list of
pins, or at least that's what we did everywhere else on sdm845 /
sc7180.

Thus to match conventions, I assume you'd do:

&qup_spi2_default {
  pinconf {
    pins = "gpio27", "gpio28", "gpio29", "gpio30";
    drive-strength = <16>;
  };
};

We've since moved away from this to a less cumbersome approach, but
for "older" boards like db845c we should probably match the existing
convention, or have a flag day and change all sdm845 boards over to
the new convention.

-Doug

On 30/09/2022 22:19, Doug Anderson wrote:
> Hi,
> 
> On Fri, Sep 30, 2022 at 11:22 AM Krzysztof Kozlowski
> <krzysztof.kozlowski@linaro.org> wrote:
>>
>> There is no "bias-no-pull" property.  Assume intentions were disabling
>> bias.
>>
>> Fixes: b190fb010664 ("arm64: dts: qcom: sdm630: Add sdm630 dts file")
>> Cc: <stable@vger.kernel.org>
>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
>>
>> ---
>>
>> Not tested on hardware.
>> ---
>>  arch/arm64/boot/dts/qcom/sdm630.dtsi | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> This does change behavior and has the potential to break someone.
> Thus, without a bug report or someone to give a tested-by I'm at least
> moderately worried about this going to stable@

Indeed. I can drop Cc-stable, but AUTOSEL can still pick it up because
of Fixes tag. Fixes tag is here important to indicate we are having a
bug before.

> 
> I would also note that convention on Qualcomm SoCs that I've worked on
> was that bias shouldn't be specified in the SoC dtsi file and should
> be left to board files. This is talked a bit about in a previous email
> thread [1].

Uh, that makes a lot of sense. It is almost always a property of a board.

> 
> That being said, it does look like this was the intention of the
> original commit, so thus:
> 
> Reviewed-by: Douglas Anderson <dianders@chromium.org>

Thanks.

I can also drop the property entirely to match existing behavior (not
the intention).

> 
> [1] https://lore.kernel.org/lkml/CAD=FV=VUL4GmjaibAMhKNdpEso_Hg_R=XeMaqah1LSj_9-Ce4Q@mail.gmail.com/

Best regards,
Krzysztof

On 03/10/2022 17:40, Doug Anderson wrote:
>>>>
>>>> diff --git a/arch/arm64/boot/dts/qcom/sdm845-db845c.dts b/arch/arm64/boot/dts/qcom/sdm845-db845c.dts
>>>> index 132417e2d11e..a157eab66dee 100644
>>>> --- a/arch/arm64/boot/dts/qcom/sdm845-db845c.dts
>>>> +++ b/arch/arm64/boot/dts/qcom/sdm845-db845c.dts
>>>> @@ -1123,7 +1123,9 @@ &wifi {
>>>>
>>>>  /* PINCTRL - additions to nodes defined in sdm845.dtsi */
>>>>  &qup_spi2_default {
>>>> -       drive-strength = <16>;
>>>> +       pinmux {
>>>> +               drive-strength = <16>;
>>>> +       };
>>>
>>> The convention on Qualcomm boards of this era is that muxing (setting
>>> the function) is done under a "pinmux" node and, unless some of the
>>> pins need to be treated differently like for the UARTs, configuration
>>> (bias, drive strength, etc) is done under a "pinconf" subnode.
>>
>> Yes, although this was not expressed in bindings.
>>
>>> I
>>> believe that the "pinconf" subnode also needs to replicate the list of
>>> pins, or at least that's what we did everywhere else on sdm845 /
>>> sc7180.
>>
>> Yes.
>>
>>>
>>> Thus to match conventions, I assume you'd do:
>>>
>>> &qup_spi2_default {
>>>   pinconf {
>>
>> No, because I want a convention of all pinctrl bindings and drivers, not
>> convention of old pinctrl ones. The new ones are already moved or being
>> moved to "-state" and "-pins". In the same time I am also unifying the
>> requirement of "function" property - enforcing it in each node, thus
>> "pinconf" will not be valid anymore.
> 
> Regardless of where we want to end up, it feels like as of ${SUBJECT}
> patch this should match existing conventions in this file. If a later
> patch wants to change the conventions in this file then it can, but
> having just this one patch leaving things in an inconsistent state
> isn't great IMO...
> 
> If this really has to be one-off then the subnode shouldn't be called
> "pinmux". A subnode called "pinmux" implies that it just has muxing
> information in it. After your patch this is called "pinmux" but has
> _configuration_ in it.
> 

It is a poor argument to keep some convention which is both
undocumented, not kept in this file and known only to some folks
(although that's effect of lack of documentation). Even the bindings do
not say it should be "pinconf" but they mention "config" in example. The
existing sdm845.dts uses config - so why now there should be "pinconf"?
By this "convention" we have both "pinmux" and "mux", perfect. Several
other pins do not have pinmux/mux/config at all.

This convention was never implemented, so there is nothing to keep/match.

Changing it to "config" (because this is the most used "convention" in
the file and bindings) would also mean to add useless "pins" which will
be in next patch removed.

Best regards,
Krzysztof

Hi,

On Mon, Oct 3, 2022 at 10:57 AM Krzysztof Kozlowski
<krzysztof.kozlowski@linaro.org> wrote:
>
> On 03/10/2022 17:40, Doug Anderson wrote:
> >>>>
> >>>> diff --git a/arch/arm64/boot/dts/qcom/sdm845-db845c.dts b/arch/arm64/boot/dts/qcom/sdm845-db845c.dts
> >>>> index 132417e2d11e..a157eab66dee 100644
> >>>> --- a/arch/arm64/boot/dts/qcom/sdm845-db845c.dts
> >>>> +++ b/arch/arm64/boot/dts/qcom/sdm845-db845c.dts
> >>>> @@ -1123,7 +1123,9 @@ &wifi {
> >>>>
> >>>>  /* PINCTRL - additions to nodes defined in sdm845.dtsi */
> >>>>  &qup_spi2_default {
> >>>> -       drive-strength = <16>;
> >>>> +       pinmux {
> >>>> +               drive-strength = <16>;
> >>>> +       };
> >>>
> >>> The convention on Qualcomm boards of this era is that muxing (setting
> >>> the function) is done under a "pinmux" node and, unless some of the
> >>> pins need to be treated differently like for the UARTs, configuration
> >>> (bias, drive strength, etc) is done under a "pinconf" subnode.
> >>
> >> Yes, although this was not expressed in bindings.
> >>
> >>> I
> >>> believe that the "pinconf" subnode also needs to replicate the list of
> >>> pins, or at least that's what we did everywhere else on sdm845 /
> >>> sc7180.
> >>
> >> Yes.
> >>
> >>>
> >>> Thus to match conventions, I assume you'd do:
> >>>
> >>> &qup_spi2_default {
> >>>   pinconf {
> >>
> >> No, because I want a convention of all pinctrl bindings and drivers, not
> >> convention of old pinctrl ones. The new ones are already moved or being
> >> moved to "-state" and "-pins". In the same time I am also unifying the
> >> requirement of "function" property - enforcing it in each node, thus
> >> "pinconf" will not be valid anymore.
> >
> > Regardless of where we want to end up, it feels like as of ${SUBJECT}
> > patch this should match existing conventions in this file. If a later
> > patch wants to change the conventions in this file then it can, but
> > having just this one patch leaving things in an inconsistent state
> > isn't great IMO...
> >
> > If this really has to be one-off then the subnode shouldn't be called
> > "pinmux". A subnode called "pinmux" implies that it just has muxing
> > information in it. After your patch this is called "pinmux" but has
> > _configuration_ in it.
> >
>
> It is a poor argument to keep some convention which is both
> undocumented, not kept in this file and known only to some folks
> (although that's effect of lack of documentation). Even the bindings do
> not say it should be "pinconf" but they mention "config" in example. The
> existing sdm845.dts uses config - so why now there should be "pinconf"?
> By this "convention" we have both "pinmux" and "mux", perfect. Several
> other pins do not have pinmux/mux/config at all.
>
> This convention was never implemented, so there is nothing to keep/match.
>
> Changing it to "config" (because this is the most used "convention" in
> the file and bindings) would also mean to add useless "pins" which will
> be in next patch removed.

I certainly won't make the argument that the old convention was great
or even that consistently followed. That's why it changed. ...but to
me it's more that a patch should stand on its own and not only make
sense in the context of future patches. After applying ${SUBJECT}
patch you end up with a node called "pinmux" that has more than just
muxing information in it. That seems less than ideal.

-Doug