On 9/3/2025 1:52 PM, Krzysztof Kozlowski wrote:
On 03/09/2025 10:04, Sarthak Garg wrote:
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 <quic_sartgarg@xxxxxxxxxxx>
---
.../devicetree/bindings/mmc/mmc-controller-common.yaml | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/Documentation/devicetree/bindings/mmc/mmc-controller-common.yaml b/Documentation/devicetree/bindings/mmc/mmc-controller-common.yaml
index 9a7235439759..d6b785cb2bd9 100644
--- a/Documentation/devicetree/bindings/mmc/mmc-controller-common.yaml
+++ b/Documentation/devicetree/bindings/mmc/mmc-controller-common.yaml
@@ -93,6 +93,14 @@ properties:
minimum: 400000
maximum: 384000000
+ max-sd-hs-hz:
+ 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.
+ default: 50000000
no minimum/maximum? If 50 MHz is default, isn't it also an actual max?
Best regards,
Krzysztof
I realized I had misinterpreted your earlier comment, which led to the
removal of min/max. I’ll reintroduce them with the following values:
+ minimum: 400000
+ maximum: 50000000
+ default: 50000000
Regarding your comment on V4 — "Don't repeat constraints in free form
text" — just to clarify: are you suggesting that I remove the sentence:
"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."
If so, I’ll go ahead and remove it from the bindings.
Best regards,
Sarthak
