Re: [PATCH v1 1/1] scsi: ufshcd: Properly set the device Icc Level

[nguyenb]

On 2020-09-15 06:37, Bjorn Andersson wrote:
> On Tue 15 Sep 03:49 CDT 2020, nguyenb@xxxxxxxxxxxxxx wrote:
>
> > On 2020-09-14 19:54, Bjorn Andersson wrote:
> > > On Tue 01 Sep 01:19 UTC 2020, Bao D. Nguyen wrote:
> > >
> > > > UFS version 3.0 and later devices require Vcc and Vccq power supplies
> > > > with Vccq2 being optional. While earlier UFS version 2.0 and 2.1
> > > > devices, the Vcc and Vccq2 are required with Vccq being optional.
> > > > Check the required power supplies used by the device
> > > > and set the device's supported Icc level properly.
> > > >
> > > > Signed-off-by: Can Guo <cang@xxxxxxxxxxxxxx>
> > > > Signed-off-by: Asutosh Das <asutoshd@xxxxxxxxxxxxxx>
> > > > Signed-off-by: Bao D. Nguyen <nguyenb@xxxxxxxxxxxxxx>
> > > > ---
> > > >  drivers/scsi/ufs/ufshcd.c | 5 +++--
> > > >  1 file changed, 3 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> > > > index 06e2439..fdd1d3e 100644
> > > > --- a/drivers/scsi/ufs/ufshcd.c
> > > > +++ b/drivers/scsi/ufs/ufshcd.c
> > > > @@ -6845,8 +6845,9 @@ static u32
> > > > ufshcd_find_max_sup_active_icc_level(struct ufs_hba *hba,
> > > >  {
> > > >  	u32 icc_level = 0;
> > > >
> > > > -	if (!hba->vreg_info.vcc || !hba->vreg_info.vccq ||
> > > > -						!hba->vreg_info.vccq2) {
> > > > +	if (!hba->vreg_info.vcc ||
> > >
> > > How did you test this?
> > >
> > > devm_regulator_get() never returns NULL, so afaict this conditional will
> > > never be taken with either the old or new version of the code.
> > Thanks for your comment. The call flow is as follows:
> > ufshcd_pltfrm_init->ufshcd_parse_regulator_info->ufshcd_populate_vreg
> > In the ufshcd_populate_vreg() function, it looks for DT entries 
> > "%s-supply"
> > For UFS3.0+ devices, "vccq2-supply" is optional, so the vendor may 
> > choose
> > not to provide vccq2-supply in the DT.
> > As a result, a NULL is returned to hba->vreg_info.vccq2.
> > Same for UFS2.0 and UFS2.1 devices, a NULL may be returned to
> > hba->vreg_info.vccq if vccq-supply is not provided in the DT.
> > The current code only checks for !hba->vreg_info.vccq OR
> > !hba->vreg_info.vccq2. It will skip the setting for icc_level
> > if either vccq or vccq2 is not provided in the DT.
> > >
>
> Thanks for the pointers, I now see that the there will only be struct
> ufs_vreg objects allocated for the items that has an associated
> %s-supply.
>
> FYI, the idiomatic way to handle optional regulators is to use
> regulator_get_optional(), which will return -ENODEV for regulators not
> specified.
Thanks for the regulator_get_optional() suggestion. Do you have a strong 
opinion about
using regulator_get_optional() or would my proposal be ok? With 
regulator_get_optional(),
we need to make 3 calls and check each result while the current 
implementation is also reliable
simple quick check for NULL without any potential problem.

Thanks,
Bao
> Regards,
> Bjorn
>
> > > Regards,
> > > Bjorn
> > >
> > > > +		(!hba->vreg_info.vccq && hba->dev_info.wspecversion >= 0x300) ||
> > > > +		(!hba->vreg_info.vccq2 && hba->dev_info.wspecversion < 0x300)) {
> > > >  		dev_err(hba->dev,
> > > >  			"%s: Regulator capability was not set, actvIccLevel=%d",
> > > >  							__func__, icc_level);
> > > > --
> > > > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
> > > > Forum,
> > > > a Linux Foundation Collaborative Project
> > > >