linux-kernel - Re: [PATCH v2 03/11] dt-bindings: regulator: pca9450: Document nxp,sd-vsel-fixed-low property for LDO5

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Message-ID: <9276fad1-0e3c-4935-a62a-1580af2e0a4b@kontron.de>
Date: Tue, 10 Dec 2024 16:36:41 +0100
From: Frieder Schrempf <frieder.schrempf@...tron.de>
To: Conor Dooley <conor@...nel.org>, Frieder Schrempf <frieder@...s.de>
Cc: linux-arm-kernel@...ts.infradead.org, Marek Vasut <marex@...x.de>,
 Conor Dooley <conor+dt@...nel.org>, devicetree@...r.kernel.org,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Liam Girdwood
 <lgirdwood@...il.com>, linux-kernel@...r.kernel.org,
 Mark Brown <broonie@...nel.org>, Rob Herring <robh@...nel.org>,
 Robin Gong <yibin.gong@....com>, Joy Zou <joy.zou@....com>,
 Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Subject: Re: [PATCH v2 03/11] dt-bindings: regulator: pca9450: Document
 nxp,sd-vsel-fixed-low property for LDO5

On 28.11.24 6:33 PM, Conor Dooley wrote:
> On Wed, Nov 27, 2024 at 05:42:19PM +0100, Frieder Schrempf wrote:
>> From: Frieder Schrempf <frieder.schrempf@...tron.de>
>>
>> This new property can be used for boards which have the SD_VSEL tied
>> to a fixed low level. The voltage of LDO5 is therefore only controlled
>> by writing to the LDO5CTRL_L register.
>>
>> Signed-off-by: Frieder Schrempf <frieder.schrempf@...tron.de>
>> ---
>> Changes for v2:
>> * new patch
>> ---
>>  .../bindings/regulator/nxp,pca9450-regulator.yaml           | 6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/regulator/nxp,pca9450-regulator.yaml b/Documentation/devicetree/bindings/regulator/nxp,pca9450-regulator.yaml
>> index 5d0d684186c96..0e19c54aa5f8a 100644
>> --- a/Documentation/devicetree/bindings/regulator/nxp,pca9450-regulator.yaml
>> +++ b/Documentation/devicetree/bindings/regulator/nxp,pca9450-regulator.yaml
>> @@ -49,6 +49,12 @@ properties:
>>            Properties for single LDO5 regulator.
>>  
>>          properties:
>> +          nxp,sd-vsel-fixed-low:
>> +            type: boolean
>> +            description:
>> +              Let the driver know that SD_VSEL is hardwired to low level and
>> +              there is no GPIO to get the actual value from.
> 
> Does this mean that if you don't provide the property or a GPIO it is tied
> high or High-Z? If so, please mention it here. More likely, given the
> context of this patch, no gpio and no tied low property means the driver
> should handle things as they used to be - but you should call that out
> in your commit message to be clear.

Providing neither 'sd-vsel-gpios', nor 'nxp,sd-vsel-fixed-low' means the
driver has to assume that SD_VSEL is tied high and it has to use the
LDO5CTRL_H for voltage control.

I will make this more clear in the commit message.

This is the original/current behavior of the driver, though it doesn't
match the actual hardware as all known boards actually have the SD_VSEL
connected to the USDHC_VSELECT (which changes state whenever the USDHC
controller wants to switch IO voltage).

Getting rid of this mismatch is one of the main motivations for this series.

> 
>> +
>>            sd-vsel-gpios:
>>              description:
>>                GPIO that can be used to read the current status of the SD_VSEL
>> -- 
>> 2.46.1
>>