Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Mon, 21 Dec 2020 11:35:46 -0800
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Avri Altman <Avri.Altman@wdc.com>
Cc:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
        "kernel-team@android.com" <kernel-team@android.com>,
        "cang@codeaurora.org" <cang@codeaurora.org>,
        "alim.akhtar@samsung.com" <alim.akhtar@samsung.com>,
        "bvanassche@acm.org" <bvanassche@acm.org>,
        "martin.petersen@oracle.com" <martin.petersen@oracle.com>,
        "stanley.chu@mediatek.com" <stanley.chu@mediatek.com>
Subject: Re: [PATCH] scsi: ufs: fix livelock of ufshcd_clear_ua_wluns
Message-ID: <X+D5EhJ8QzNoeHQw@google.com>
References: <20201218033131.2624065-1-jaegeuk@kernel.org>
 <DM6PR04MB6575B8729A62E6FB9F19930CFCC10@DM6PR04MB6575.namprd04.prod.outlook.com>
 <X+C9+1p1CbssKRdO@google.com>
 <DM6PR04MB65753B9D31B3643C757E4E23FCC00@DM6PR04MB6575.namprd04.prod.outlook.com>
 <X+DZMwSHsskcEgZE@google.com>
 <DM6PR04MB657558D8353199D53586F654FCC00@DM6PR04MB6575.namprd04.prod.outlook.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <DM6PR04MB657558D8353199D53586F654FCC00@DM6PR04MB6575.namprd04.prod.outlook.com>
Precedence: bulk

On 12/21, Avri Altman wrote:
> > 
> > 
> > On 12/21, Avri Altman wrote:
> > > > > > When gate_work/ungate_work gets an error during hibern8_enter or
> > > > exit,
> > > > > >  ufshcd_err_handler()
> > > > > >    ufshcd_scsi_block_requests()
> > > > > >    ufshcd_reset_and_restore()
> > > > > >      ufshcd_clear_ua_wluns() -> stuck
> > > > > >    ufshcd_scsi_unblock_requests()
> > > > > >
> > > > > > 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.