Re: [PATCH v2 2/4] scsi: ufs: Update VCCQ2 and VCCQ min/max voltage hard codes

[cang]

On 2019-11-19 20:41, Avri Altman wrote:
> > On 2019-11-18 15:15, Avri Altman wrote:
> > >>
> > >> From: Can Guo <cang@xxxxxxxxxxxxxx>
> > >>
> > >> Per UFS 3.0 JEDEC standard, the VCCQ2 min voltage is 1.7v and the
> > >> VCCQ voltage range is 1.14v ~ 1.26v. Update their hard codes
> > >> accordingly to make sure they work in a safe range compliant for ver
> > >> 1.0/2.0/2.1/3.0 UFS devices.
> > > So to keep it safe, we need to use largest range:
> > > min_uV = min over all spec ranges, and max_uV = max over all spec
> > > ranges.
> > > Meaning leave it as it is if we want to be backward compatible with
> > > UFS1.0.
> > >
> > > Thanks,
> > > Avri
> > >
> >
> > Hi Avri,
> >
> > Sorry I don't quite follow you here.
> > Leaving it as it is means for UFS2.1 devices, when boot up, if we call
> > regulator_set_voltage(1.65, 1.95) to setup its VCCQ2,
> > regulator_set_voltage() will
> > give you 1.65v on VCCQ2 if the voltage level of this regulator is 
> > wider, say (1.60,
> > 1.95).
> > Meaning you will finally set 1.65v to VCCQ2. But 1.65v is out of spec 
> > for UFS
> > v2.1 as it requires min voltage to be 1.7v on VCCQ2. So, the smallest 
> > range is
> > safe.
> > Of course, in real board design, the regulator's voltage level is 
> > limited/designed
> > by power team to be in a safe range, say (1.8, 1.92), so that calling
> > regulator_set_voltage(1.65, 1.95) still gives you 1.8v. But it does 
> > not mean the
> > current hard codes are compliant for all UFS devices.
> You are correct - the narrowest the range the better - as long as you
> don't cross the limits of previous spec.
> So changing 1.1 -> 1.14  and 1.65 -> 1.7 is fine.
> While at it, Vccq max in UFS3.0 is 1.26, why not change 1.3 -> 1.26,
> like you indicated in your commit log?
>
> Thanks,
> Avri

Thank you Avri, sorry I missed the change to max voltage of VCCQ, I
will update it in the next version.

Best Regards,
Can Guo.

> > Best Regards,
> > Can Guo.
> >
> > >>
> > >> Signed-off-by: Can Guo <cang@xxxxxxxxxxxxxx>
> > >> ---
> > >>  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