linux-kernel - Re: [PATCH v2 1/2] spi: dt-bindings: amlogic, meson-gx-spicc: Add pinctrl names for SPI signal states

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Date:   Thu, 6 Oct 2022 17:48:49 +0200
From:   Neil Armstrong <neil.armstrong@...aro.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Amjad Ouled-Ameur <aouledameur@...libre.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Kevin Hilman <khilman@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Mark Brown <broonie@...nel.org>
Cc:     Da Xue <da@...re.computer>, linux-kernel@...r.kernel.org,
        linux-spi@...r.kernel.org, linux-amlogic@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 1/2] spi: dt-bindings: amlogic, meson-gx-spicc: Add
 pinctrl names for SPI signal states

On 06/10/2022 16:11, Krzysztof Kozlowski wrote:
> On 06/10/2022 12:57, Amjad Ouled-Ameur wrote:
>> Hi Krzysztof,
>>
>> Thank you for the review.
>>
>> On 10/5/22 10:14, Krzysztof Kozlowski wrote:
>>> On 04/10/2022 13:10, Amjad Ouled-Ameur wrote:
>>>> SPI pins of the SPICC Controller in Meson-GX needs to be controlled by
>>>> pin biais when idle. Therefore define three pinctrl names:
>>>> - default: SPI pins are controlled by spi function.
>>>> - idle-high: SCLK pin is pulled-up, but MOSI/MISO are still controlled
>>>> by spi function.
>>>> - idle-low: SCLK pin is pulled-down, but MOSI/MISO are still controlled
>>>> by spi function.
>>>>
>>>> Reported-by: Da Xue <da@...re.computer>
>>>> Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
>>>> Signed-off-by: Amjad Ouled-Ameur <aouledameur@...libre.com>
>>>> ---
>>>>    .../devicetree/bindings/spi/amlogic,meson-gx-spicc.yaml   | 15 +++++++++++++++
>>>>    1 file changed, 15 insertions(+)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/spi/amlogic,meson-gx-spicc.yaml b/Documentation/devicetree/bindings/spi/amlogic,meson-gx-spicc.yaml
>>>> index 0c10f7678178..53013e27f507 100644
>>>> --- a/Documentation/devicetree/bindings/spi/amlogic,meson-gx-spicc.yaml
>>>> +++ b/Documentation/devicetree/bindings/spi/amlogic,meson-gx-spicc.yaml
>>>> @@ -43,6 +43,14 @@ properties:
>>>>        minItems: 1
>>>>        maxItems: 2
>>>>    
>>>> +  pinctrl-0:
>>>> +    minItems: 1
>>> maxItems?
>>>
>> Will fill it in next version.
>>>> +
>>>> +  pinctrl-1:
>>>> +    maxItems: 1
>>>> +
>>>> +  pinctrl-names: true
>>> Why do you need all these in the bindings?
>>
>> SPI clock bias needs to change at runtime depending on SPI mode, here is an example of
>>
>> how this is supposed to be used ("spi_idle_low_pins" and "spi_idle_low_pins" are defined
>>
>> in the second patch of this series):
> 
> I know what it the point in general of pinctrl configuration... But the
> question is why do you need to specify them in the bindings? Core
> handles that. IOW, do you require them and missing/incomplete pinctrl
> should be reported?

Looking at other bindings, when specific pinctrl state names were requires, they were
documented.

There's some bindings with pinctrl-names for specific states like rockchip/rockchip,dw-hdmi.yaml,
mediatek/mediatek,dpi.yaml, mmc/mtk-sd.yaml or mmc/fsl-imx-esdhc.yaml

Neil


> 
> Best regards,
> Krzysztof
>