linux-kernel - Re: [PATCH 2/3] scsi: ufs: Keep device power on only fWriteBoosterBufferFlushDuringHibernate == 1

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Date:   Thu, 03 Dec 2020 10:40:30 +0100
From:   Bean Huo <huobean@...il.com>
To:     Avri Altman <Avri.Altman@....com>,
        "alim.akhtar@...sung.com" <alim.akhtar@...sung.com>,
        "asutoshd@...eaurora.org" <asutoshd@...eaurora.org>,
        "jejb@...ux.ibm.com" <jejb@...ux.ibm.com>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "stanley.chu@...iatek.com" <stanley.chu@...iatek.com>,
        "beanhuo@...ron.com" <beanhuo@...ron.com>,
        "bvanassche@....org" <bvanassche@....org>,
        "tomas.winkler@...el.com" <tomas.winkler@...el.com>,
        "cang@...eaurora.org" <cang@...eaurora.org>
Cc:     "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] scsi: ufs: Keep device power on only
 fWriteBoosterBufferFlushDuringHibernate == 1

On Thu, 2020-12-03 at 07:27 +0000, Avri Altman wrote:
> > 
> > From: Bean Huo <beanhuo@...ron.com>
> > 
> > Keep device power mode as active power mode and VCC supply only if
> > fWriteBoosterBufferFlushDuringHibernate setting 1 is successful.

Hi Avri
Thanks so much taking time reiew.

> Why would it fail?

During the reliability testing in harsh environments, such as:
EMS testing, in the high/low-temperature environment. The system would
reboot itself, there will be programming failure very likely.
If we assume failure will never hit, why we capture its result
following with dev_err(). If you keep using your phone in a harsh
environment, you will see this print message.

Of course, in a normal environment, the chance of failure likes you to
win a lottery, but the possibility still exists.

> Since UFSHCD_CAP_WB_EN is toggled off on ufshcd_wb_probe If the
> device doesn't support wb,
> The check ufshcd_is_wb_allowed should suffice, isn't it?
> 

No, UFSHCD_CAP_WB_EN only tells us if the platform supports WB,
doesn't tell us fWriteBoosterBufferFlushDuringHibernate status.

Thanks,
Bean