Re: [PATCH V3 2/4] dt-bindings: mmc: controller: Add max-sd-hs-frequency property

[Sarthak Garg]

On 6/18/2025 2:38 PM, Krzysztof Kozlowski wrote:
> On 18/06/2025 10:38, Sarthak Garg wrote:
> > On 6/18/2025 1:13 PM, Krzysztof Kozlowski wrote:
> > > On 18/06/2025 09:28, Sarthak Garg wrote:
> > > > Introduce a new optional device tree property `max-sd-hs-frequency` to
> > > > limit the maximum frequency (in Hz) used for SD cards operating in
> > > > High-Speed (HS) mode.
> > > >
> > > > This property is useful for platforms with vendor-specific hardware
> > > > constraints, such as the presence of a level shifter that cannot
> > > > reliably support the default 50 MHz HS frequency. It allows the host
> > > > driver to cap the HS mode frequency accordingly.
> > > >
> > > > Signed-off-by: Sarthak Garg <quic_sartgarg@xxxxxxxxxxx>
> > > > ---
> > > >    .../devicetree/bindings/mmc/mmc-controller-common.yaml | 10 ++++++++++
> > > >    1 file changed, 10 insertions(+)
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/mmc/mmc-controller-common.yaml b/Documentation/devicetree/bindings/mmc/mmc-controller-common.yaml
> > > > index 9a7235439759..1976f5f8c401 100644
> > > > --- a/Documentation/devicetree/bindings/mmc/mmc-controller-common.yaml
> > > > +++ b/Documentation/devicetree/bindings/mmc/mmc-controller-common.yaml
> > > > @@ -93,6 +93,16 @@ properties:
> > > >        minimum: 400000
> > > >        maximum: 384000000
> > > >    
> > > > +  max-sd-hs-frequency:
> > > > +    $ref: /schemas/types.yaml#/definitions/uint32
> > > > +    description: |
> > > > +      Maximum frequency (in Hz) to be used for SD cards operating in
> > > > +      High-Speed (HS) mode. This is useful for platforms with vendor-specific
> > > > +      limitations, such as the presence of a level shifter that cannot support
> > > > +      the default 50 MHz HS frequency or other.
> > > > +    minimum: 400000
> > > > +    maximum: 50000000
> > >
> > > This might be fine, but your DTS suggests clearly this is SoC compatible
> > > deducible, which I already said at v1.
> > >
> > > So now you send v3 which is the same as v1, so you get the same comments.
> > >
> > > Best regards,
> > > Krzysztof
> >
> > Introducing this flag no longer becomes SoC compatible because as per
> > discussions in V2 patchset with Ulf and Konrad this new property can be
> > used by any vendor who wants to limit the HS mode frequency due to any
> > reason. Thats why moved to this generic approach again in V3 as compared
> > to compatible based approach in V2.
>
> The are no arguments provided in favor, so my review from v1 stays. You
> get the same comments.
>
> Best regards,
> Krzysztof

@Ulf, @Konrad — since you previously supported the idea of a generic 
property for HS frequency limitation, could you please share your 
thoughts on whether this still seems like a valid approach?

Best regards,
Sarthak