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: <20241216-reburial-turmoil-4825bbee6aa8@spud>
Date: Mon, 16 Dec 2024 19:50:53 +0000
From: Conor Dooley <conor@...nel.org>
To: Frieder Schrempf <frieder.schrempf@...tron.de>
Cc: Frieder Schrempf <frieder@...s.de>,
	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 Tue, Dec 10, 2024 at 04:36:41PM +0100, Frieder Schrempf wrote:
> 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).

That's fine, as long as it is a match for the old behaviour. Sorry for
the delay responding, I was unexpectedly AFK last week.

> 
> 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
> >>
> 

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