linux-kernel - RE: [PATCH] scsi: ufs: fix livelock of ufshcd_clear_ua

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Date:   Mon, 21 Dec 2020 20:13:59 +0000
From:   Avri Altman <Avri.Altman@....com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "kernel-team@...roid.com" <kernel-team@...roid.com>,
        "cang@...eaurora.org" <cang@...eaurora.org>,
        "alim.akhtar@...sung.com" <alim.akhtar@...sung.com>,
        "bvanassche@....org" <bvanassche@....org>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "stanley.chu@...iatek.com" <stanley.chu@...iatek.com>
Subject: RE: [PATCH] scsi: ufs: fix livelock of ufshcd_clear_ua_wluns

> > > > > > > In order to avoid it, ufshcd_clear_ua_wluns() can be called per
> > > recovery
> > > > > > > flows
> > > > > > > such as suspend/resume, link_recovery, and error_handler.
> > > > > > Not sure that suspend/resume are UAC events?
> > > > >
> > > > > Could you elaborate a bit? The goal is to clear UAC after UFS reset
> > > happens.
> > > > So why calling it on every suspend and resume?
> > >
> > > 1. If UAC was cleared, there's no impact.
> > But the command is still sent.
> 
> No, ufshcd_clear_ua_wluns() will return by hba->wlun_dev_clr_ua.
> 
> >
> > > 2. ufshcd_link_recovery() can reset UFS directly by ufs_mtk_resume().
> > > 3. ufshcd_suspend can call ufshcd_host_reset_and_restore() as well.
> > Seems excessive IMO.
> > Why not selectively send when indeed required, e.g. on reset?
> 
> I think hba->wlun_dev_clr_ua is the indicator whether there was a reset or
> not.
Ahha - I missed that.  Thanks for clarifying it.
OK Then.

Thanks,
Avri