linux-kernel - Re: [PATCH] dt-bindings: mmc: fsl-imx-esdhc: allow more compatible combinations

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Date:   Fri, 6 Jan 2023 20:33:58 +0100
From:   Andreas Kemnade <andreas@...nade.info>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     ulf.hansson@...aro.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, shawnguo@...nel.org,
        s.hauer@...gutronix.de, kernel@...gutronix.de, festevam@...il.com,
        linux-imx@....com, linux-mmc@...r.kernel.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dt-bindings: mmc: fsl-imx-esdhc: allow more compatible
 combinations

On Fri, 6 Jan 2023 09:41:01 +0100
Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> wrote:

> On 05/01/2023 22:38, Andreas Kemnade wrote:
> > Currently make dtbs_check shows lots of errors because imx*.dtsi does
> > not use single compatibles but combinations of them.
> > Allow all the combinations used there.
> > 
> > Patches fixing the dtsi files according to binding documentation were
> > submitted multiple times and are commonly rejected, so relax the rules.
> > Example:
> > https://lore.kernel.org/linux-devicetree/72e1194e10ccb4f87aed96265114f0963e805092.camel@pengutronix.de/
> > 
> > Reason: compatibility of new dtbs with old kernels or bootloaders.
> > 
> > This will significantly reduce noise on make dtbs_check.
> > 
> > Signed-off-by: Andreas Kemnade <andreas@...nade.info>
> > ---
> >  .../bindings/mmc/fsl-imx-esdhc.yaml           | 24 +++++++++++++++++++
> >  1 file changed, 24 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/mmc/fsl-imx-esdhc.yaml b/Documentation/devicetree/bindings/mmc/fsl-imx-esdhc.yaml
> > index dc6256f04b42..118ebb75f136 100644
> > --- a/Documentation/devicetree/bindings/mmc/fsl-imx-esdhc.yaml
> > +++ b/Documentation/devicetree/bindings/mmc/fsl-imx-esdhc.yaml
> > @@ -37,6 +37,30 @@ properties:
> >            - fsl,imx8mm-usdhc
> >            - fsl,imxrt1050-usdhc
> >            - nxp,s32g2-usdhc  
> 
> You must drop the items from enum above. Binding saying:
> compatible="A"
> or:
> compatible="A", "B"
> 
> is not correct. Either A is or is not compatible with B.
> 
hmm, here we have A = B + some additional features
or
A = B + some additional features and additional quirks required.

For the latter we have e.g.
A=
static const struct esdhc_soc_data usdhc_imx6sx_data = {
        .flags = ESDHC_FLAG_USDHC | ESDHC_FLAG_STD_TUNING
                        | ESDHC_FLAG_HAVE_CAP1 | ESDHC_FLAG_HS200
                        | ESDHC_FLAG_STATE_LOST_IN_LPMODE
                        | ESDHC_FLAG_BROKEN_AUTO_CMD23,
};
B=
static const struct esdhc_soc_data usdhc_imx6sl_data = {
        .flags = ESDHC_FLAG_USDHC | ESDHC_FLAG_STD_TUNING
                        | ESDHC_FLAG_HAVE_CAP1 | ESDHC_FLAG_ERR004536
                        | ESDHC_FLAG_HS200
                        | ESDHC_FLAG_BROKEN_AUTO_CMD23,
};

so there is the difference in ESDHC_FLAG_STATE_LOST_IN_LPMODE.
That might make no difference in some usage scenario (e.g. some bootloader
not doing any LPMODE), but I wonder why
we need to *enforce* specifying such half-compatible things.

Regards,
Andreas