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

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Message-ID: <6xgsb7thoo7mquz3mxuyhliuqtvrbxj43nc6ga5qpcgcz4ro4u@doe2253ydjbj>
Date: Mon, 1 Sep 2025 09:37:26 +0530
From: Manivannan Sadhasivam <mani@...nel.org>
To: Bart Van Assche <bvanassche@....org>
Cc: Ram Kumar Dwivedi <quic_rdwivedi@...cinc.com>, alim.akhtar@...sung.com, 
	avri.altman@....com, robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org, 
	James.Bottomley@...senpartnership.com, martin.petersen@...cle.com, linux-scsi@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH V3 1/4] ufs: dt-bindings: Document gear and rate limit
 properties

On Thu, Aug 28, 2025 at 10:22:28AM GMT, Bart Van Assche wrote:
> On 8/28/25 9:45 AM, Ram Kumar Dwivedi wrote:
> > On 26-Aug-25 9:05 PM, Bart Van Assche wrote:
> > > On 8/26/25 8:08 AM, Ram Kumar Dwivedi wrote:
> > > > +  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.
> 
> Hi Ram,
> 
> Thanks for having looked this up.
> 
> Since it is much more common to refer to these rates as "Rate A" and
> "Rate B" rather than using numbers for these rates, please change the
> enumeration labels into something like "Rate_A" and "Rate_B".
> 

+1. Since this binding describes the HCI, let's stick to the terminologies in
UFSHCI spec.

- Mani

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