linux-kernel - Re: [PATCH v1 1/2] scsi: dt-bindings: ufs: Add vcc-voltage-level for UFS

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Message-ID: <748d238a3d9e53834a498c6f37f9f3c9@codeaurora.org>
Date:   Tue, 15 Sep 2020 01:14:47 -0700
From:   nguyenb@...eaurora.org
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     cang@...eaurora.org, asutoshd@...eaurora.org,
        martin.petersen@...cle.com, linux-scsi@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        Avri Altman <Avri.Altman@....com>,
        Vinod Koul <vkoul@...nel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 1/2] scsi: dt-bindings: ufs: Add vcc-voltage-level for
 UFS

On 2020-09-14 21:41, Bjorn Andersson wrote:
> On Tue 01 Sep 01:00 CDT 2020, Bao D. Nguyen wrote:
> 
>> UFS's specifications supports a range of Vcc operating
>> voltage levels. Add documentation for the UFS's Vcc voltage
>> levels setting.
>> 
>> Signed-off-by: Can Guo <cang@...eaurora.org>
>> Signed-off-by: Asutosh Das <asutoshd@...eaurora.org>
>> Signed-off-by: Bao D. Nguyen <nguyenb@...eaurora.org>
>> ---
>>  Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt | 2 ++
>>  1 file changed, 2 insertions(+)
>> 
>> diff --git a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt 
>> b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
>> index 415ccdd..7257b32 100644
>> --- a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
>> +++ b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
>> @@ -23,6 +23,8 @@ Optional properties:
>>                            with "phys" attribute, provides phandle to 
>> UFS PHY node
>>  - vdd-hba-supply        : phandle to UFS host controller supply 
>> regulator node
>>  - vcc-supply            : phandle to VCC supply regulator node
>> +- vcc-voltage-level     : specifies voltage levels for VCC supply.
>> +                          Should be specified in pairs (min, max), 
>> units uV.
> 
> What exactly are these pairs representing?
The pair is the min and max Vcc voltage request to the PMIC chip.
As a result, the regulator output voltage would only be in this range.

> 
> Is this supposed to be 3 pairs of (min,max) for vcc, vcc and vccq2 to 
> be
> passed into a regulator_set_voltage() for each regulator?
Yes, that's right. I should include the other power supplies in this 
change as well.
> 
> Or are these some sort of "operating points" for the vcc-supply?
> 
> Regards,
> Bjorn
> 
>>  - vccq-supply           : phandle to VCCQ supply regulator node
>>  - vccq2-supply          : phandle to VCCQ2 supply regulator node
>>  - vcc-supply-1p8        : For embedded UFS devices, valid VCC range 
>> is 1.7-1.95V
>> --
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora 
>> Forum,
>> a Linux Foundation Collaborative Project
>>