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

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Message-Id: <20250618072818.1667097-3-quic_sartgarg@quicinc.com>
Date: Wed, 18 Jun 2025 12:58:16 +0530
From: Sarthak Garg <quic_sartgarg@...cinc.com>
To: Ulf Hansson <ulf.hansson@...aro.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>
Cc: linux-mmc@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        quic_cang@...cinc.com, quic_nguyenb@...cinc.com,
        quic_rampraka@...cinc.com, quic_pragalla@...cinc.com,
        quic_sayalil@...cinc.com, quic_nitirawa@...cinc.com,
        quic_bhaskarv@...cinc.com, kernel@....qualcomm.com,
        Sarthak Garg <quic_sartgarg@...cinc.com>
Subject: [PATCH V3 2/4] dt-bindings: mmc: controller: Add max-sd-hs-frequency property

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@...cinc.com>
---
 .../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
+
   disable-wp:
     $ref: /schemas/types.yaml#/definitions/flag
     description:
-- 
2.34.1