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From:   Avri Altman <Avri.Altman@wdc.com>
To:     Jaegeuk Kim <jaegeuk@kernel.org>
CC:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
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        "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
Thread-Topic: [PATCH] scsi: ufs: fix livelock of ufshcd_clear_ua_wluns
Thread-Index: AQHW1O5Lq9Xt0bukCk2VnSNzzSWPAqoAjHbQgAEkMYCAABqVAIAABd2AgAAK2YA=
Date:   Mon, 21 Dec 2020 18:05:15 +0000
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>=20
>=20
> 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?
>=20
> 1. If UAC was cleared, there's no impact.
But the command is still sent.

> 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?