linux-kernel - Re: [PATCH v2 2/3] scsi: ufs: Keep device active mode only fWriteBoosterBufferFlushDuringHibernate == 1

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Message-ID: <7a66077d6e5a3590d027756941850d6058ccb40c.camel@gmail.com>
Date:   Tue, 08 Dec 2020 10:41:22 +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 v2 2/3] scsi: ufs: Keep device active mode only
 fWriteBoosterBufferFlushDuringHibernate == 1

On Tue, 2020-12-08 at 09:05 +0000, Avri Altman wrote:
> > "
> > If fWriteBoosterBufferFlushDuringHibernate ==0, device will not
> > flush
> > WB, even if you keep device as "active mode" and LINK in hibernate
> > state.
> 
> OK, so what you are actually saying, is that since we are only
> toggling this flag once per
> link startup / recovery, in case of a failure, however rare - the
> host may be still keep vcc on
> for nothing, as the device will do nothing in that extra wake time. 
> Right?
> 

again, this is a BUG, BUG...
Bug is a Bug, doesn't matter it is rare or not rare. 

Tell me why we retry three times in ufshcd_query_flag_retry() in case
of failure?


> But every time ufshcd_wb_need_flush() is called we are reading some
> other flags/attributes?
> What about them? Why not protecting them as well?
> 

did you read ufshcd_wb_need_flush() fully? they have been properly
protected.

> Sorry - the whole idea doesn't make any sense to me.
> 

Thanks very much for sharing your opinion, I am very happy to hear your
opinion. Because you don't believe this is a bug, I will ask other UFS
guys to review, let Martin make the last decision.


Thanks agaion for your review.

Bean