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

On 21/06/2025 12:20, Konrad Dybcio wrote:

On 6/18/25 9:43 AM, Krzysztof Kozlowski wrote:

quoted

On 18/06/2025 09:28, Sarthak Garg wrote:

quoted

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 <redacted>
---
 .../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.

I don't understand why you're rejecting a common solution to a problem
that surely exists outside this one specific chip from one specific
vendor, which may be caused by a multitude of design choices, including
erratic board (not SoC) electrical design

No one brought any arguments so far that common solution is needed. The
only argument provided - sm8550 - is showing this is soc design.

I don't reject common solution. I provided review at v1 to which no one
responded, no one argued, no one provided other arguments.

Best regards,
Krzysztof