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

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Message-ID: <20200915133729.GD670377@yoga>
Date:   Tue, 15 Sep 2020 08:37:29 -0500
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     nguyenb@...eaurora.org
Cc:     cang@...eaurora.org, asutoshd@...eaurora.org,
        martin.petersen@...cle.com, linux-scsi@...r.kernel.org,
        linux-arm-msm@...r.kernel.org,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        Stanley Chu <stanley.chu@...iatek.com>,
        Bean Huo <beanhuo@...ron.com>,
        Bart Van Assche <bvanassche@....org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 1/1] scsi: ufshcd: Properly set the device Icc Level

On Tue 15 Sep 03:49 CDT 2020, nguyenb@...eaurora.org 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@...eaurora.org>
> > > Signed-off-by: Asutosh Das <asutoshd@...eaurora.org>
> > > Signed-off-by: Bao D. Nguyen <nguyenb@...eaurora.org>
> > > ---
> > >  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.

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
> > >