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

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Date:   Thu, 03 Dec 2020 13:31:40 +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 12:15 +0000, Avri Altman wrote:
> > so, you agree the possiblity of failure  exists.
> 
> I was more relating to the lottery part.
It doesn't matter. even the possibility of winning a lottery is very
low, but still there is.
> > 
> > > Hence we need-not any extra logic protecting device management
> > > command failures.
> > 
> > what extra logic?
> > 
> > > 
> > > if reading the configuration pass correctly, and UFSHCD_CAP_WB_EN
> > > is
> > > set,
> > 
> > 
> > UFSHCD_CAP_WB_EN set is DRAM level. still in the cache.
> > 
> > > one should expect that any other functionality would work.
> > > 
> > 
> > No,  The programming will consume more power than reading, the
> > later setting will more possbile fail than reading.
> > 
> > > Otherwise, any non-standard behavior should be added with a
> > > quirk.
> > > 
> > 
> > NO, this is not what is standard or non-standard. This is
> > independent
> > of UFS device/controller. It is a software design. IMO, we didn't
> > deal
> > with programming status that is a potential bug. If having to
> > impose to
> > a component, do you think should be controller or device? Instead
> > of
> > addin a quirk, I prefer dropping this patch.
> 
> It seems you are adding some special treatment in case some device
> management command failed,
> A vanishingly unlikely event but a one that has significant impact
> over power consumption.

again, there is nothing with device. Obviously, you didn't do system
reliability testing in harsh environment. you don't believe this is WB
driver bug. I will send my next version patch with a fix-tag. even It
cannot merge. but I want to highlight it is a bug.

Thanks,
Bean