linux-kernel - [PATCH V2 1/4] ufs: dt-bindings: Document gear and rate limit properties

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Message-ID: <20250821101609.20235-2-quic_rdwivedi@quicinc.com>
Date: Thu, 21 Aug 2025 15:46:06 +0530
From: Ram Kumar Dwivedi <quic_rdwivedi@...cinc.com>
To: <mani@...nel.org>, <alim.akhtar@...sung.com>, <avri.altman@....com>,
        <bvanassche@....org>, <robh@...nel.org>, <krzk+dt@...nel.org>,
        <conor+dt@...nel.org>, <andersson@...nel.org>,
        <konradybcio@...nel.org>, <agross@...nel.org>,
        <James.Bottomley@...senPartnership.com>, <martin.petersen@...cle.com>
CC: <linux-arm-msm@...r.kernel.org>, <linux-scsi@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH V2 1/4] ufs: dt-bindings: Document gear and rate limit properties

Add optional "limit-hs-gear" and "limit-rate" properties to the
UFS controller common binding. These properties allow limiting
the maximum HS gear and rate.

This is useful in cases where the customer board may have signal
integrity, clock configuration or layout issues that prevent reliable
operation at higher gears. Such limitations are especially critical in
those platforms, where stability is prioritized over peak performance.

Signed-off-by: Ram Kumar Dwivedi <quic_rdwivedi@...cinc.com>
---
 .../devicetree/bindings/ufs/ufs-common.yaml      | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/Documentation/devicetree/bindings/ufs/ufs-common.yaml b/Documentation/devicetree/bindings/ufs/ufs-common.yaml
index 31fe7f30ff5b..baa978389ec7 100644
--- a/Documentation/devicetree/bindings/ufs/ufs-common.yaml
+++ b/Documentation/devicetree/bindings/ufs/ufs-common.yaml
@@ -89,6 +89,22 @@ properties:
 
   msi-parent: true
 
+  limit-hs-gear:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    minimum: 1
+    maximum: 5
+    description:
+      Restricts the maximum HS gear used in both TX and RX directions,
+      typically for hardware or power constraints in automotive use cases.
+
+  limit-rate:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    enum: [1, 2]
+    description:
+      Restricts the UFS controller to Rate A (1) or Rate B (2) for both
+      TX and RX directions, often required in automotive environments due
+      to hardware limitations.
+
 dependencies:
   freq-table-hz: [ clocks ]
   operating-points-v2: [ clocks, clock-names ]
-- 
2.50.1