Re: [PATCH V3 1/4] ufs: dt-bindings: Document gear and rate limit properties

On 26-Aug-25 9:05 PM, Bart Van Assche wrote:

On 8/26/25 8:08 AM, Ram Kumar Dwivedi wrote:

quoted

+  limit-hs-gear:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    minimum: 1
+    maximum: 5
+    default: 5
+    description:
+      Restricts the maximum HS gear used in both TX and RX directions,
+      typically for hardware or power constraints in automotive use cases.

The UFSHCI 5.0 spec will add gear 6 soon. So why to restrict the maximum
gear to 5?

quoted

+  limit-rate:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    enum: [1, 2]
+    default: 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.

As far as I know no numeric values are associated with these rates in
the UFSHCI 4.1 standard nor in any of the previous versions of this
standard. Does the .yaml syntax support something like "enum: [A, B]"?

Hi Bart,

As per the MIPI UniPro spec:

In Section 5.7.12.3.2, the hs_series is defined as:
hs_series = Flags[3] + 1;

In Section 5.7.7.1, Flags[3] is described as:
Set to ‘0’ for Series A and ‘1’ for Series B (PA_HSSeries).

While issuing the DME command from the UFS driver to set the rate,
the values 1 and 2 are passed as arguments for Rate A and Rate B
respectively. Additionally, the hs_rate variable is of type u32.

Thanks,
Ram

Thanks,

Bart.