linux-kernel - Re: [PATCH v1 3/5] scsi: ufs: Update VCCQ2 and VCCQ min voltage hard codes

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Date:   Wed, 13 Nov 2019 10:56:22 +0800
From:   cang@...eaurora.org
To:     Avri Altman <Avri.Altman@....com>
Cc:     asutoshd@...eaurora.org, nguyenb@...eaurora.org,
        rnayak@...eaurora.org, linux-scsi@...r.kernel.org,
        kernel-team@...roid.com, saravanak@...gle.com, salyzyn@...gle.com,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Pedro Sousa <pedrom.sousa@...opsys.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Tomas Winkler <tomas.winkler@...el.com>,
        Subhash Jadavani <subhashj@...eaurora.org>,
        Stanley Chu <stanley.chu@...iatek.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 3/5] scsi: ufs: Update VCCQ2 and VCCQ min voltage hard
 codes

On 2019-11-12 15:56, Avri Altman wrote:
>> 
>> 
>> Per UFS 3.0 JEDEC standard, the VCCQ2 min voltage is 1.7v and the VCCQ 
>> min
>> voltage is 1.14v, update their hard codes accordingly.
>> 
>> Signed-off-by: Can Guo <cang@...eaurora.org>
> AFAIK, Vccq2 is 1.7 - 1.95 in UFS2.1 as well.
> Current constants applies to UFS1.1, as indicated in the original 
> patch.
> Vccq is <1.1 - 1.3> in UFS2.1,  and <1.14 - 1.26>, so need to update
> the max as well, and
> make the assignments in ufshcd_populate_vreg depends on 
> hba->ufs_version?
> 

Hi Avri,

Thank you for the comments. I will also update max voltage of VCCQ in 
next series.

BTW, making the assignments in ufshcd_populate_vregs depends on 
hba->ufs_version is
not practical. #1. hba->ufs_version is only get after vregs and clocks 
are ON,
which is way after ufshcd_populate_vregs. #2. hba->ufs_version is the 
version
of HCI, but we need to know the version of the connected UFS device.

The purpose of this change is to make sure the voltages of VCCQ and 
VCCQ2 work in
a safe range for all ver 1.1/2.0/2.1/3.0 UFS devices that can be 
connected to a host.

Best Regards,
Can Guo.

>> ---
>>  drivers/scsi/ufs/ufs.h | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>> 
>> diff --git a/drivers/scsi/ufs/ufs.h b/drivers/scsi/ufs/ufs.h index 
>> 385bac8..9df4f4d
>> 100644
>> --- a/drivers/scsi/ufs/ufs.h
>> +++ b/drivers/scsi/ufs/ufs.h
>> @@ -500,9 +500,9 @@ struct ufs_query_res {
>>  #define UFS_VREG_VCC_MAX_UV       3600000 /* uV */
>>  #define UFS_VREG_VCC_1P8_MIN_UV    1700000 /* uV */
>>  #define UFS_VREG_VCC_1P8_MAX_UV    1950000 /* uV */
>> -#define UFS_VREG_VCCQ_MIN_UV      1100000 /* uV */
>> +#define UFS_VREG_VCCQ_MIN_UV      1140000 /* uV */
>>  #define UFS_VREG_VCCQ_MAX_UV      1300000 /* uV */
>> -#define UFS_VREG_VCCQ2_MIN_UV     1650000 /* uV */
>> +#define UFS_VREG_VCCQ2_MIN_UV     1700000 /* uV */
>>  #define UFS_VREG_VCCQ2_MAX_UV     1950000 /* uV */
>> 
>>  /*
>> --
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora 
>> Forum,
>> a Linux Foundation Collaborative Project