Re: [PATCH V4 2/4] dt-bindings: mmc: controller: Add max-sd-hs-frequency property
From: Krzysztof Kozlowski <krzk@kernel.org>
Date: 2025-08-01 09:00:45
Also in:
linux-arm-msm, linux-mmc, lkml
On 01/08/2025 10:45, Sarthak Garg wrote:
quoted hunk ↗ jump to hunk
Some platforms may require limiting the maximum frequency used in SD High-Speed (HS) mode due to board-level hardware constraints. For example, certain boards may include level shifters or other components that cannot reliably operate at the default 50 MHz HS frequency. 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. 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..6c2529b976d1 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:
Use standard unit suffixes. s/frequency/hz/
+ $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 board-specific limitations, + such as level shifters or others where the card cannot reliably + operate at the default 50 MHz HS frequency.
Don't repeat constraints in free form text. default: