linux-kernel - RE: [PATCH v5 7/7] scsi: ufs: Fix error handing during hibern8 enter

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Date:   Fri, 15 Nov 2019 10:12:27 +0000
From:   Avri Altman <Avri.Altman@....com>
To:     Can Guo <cang@...eaurora.org>,
        "asutoshd@...eaurora.org" <asutoshd@...eaurora.org>,
        "nguyenb@...eaurora.org" <nguyenb@...eaurora.org>,
        "rnayak@...eaurora.org" <rnayak@...eaurora.org>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "kernel-team@...roid.com" <kernel-team@...roid.com>,
        "saravanak@...gle.com" <saravanak@...gle.com>,
        "salyzyn@...gle.com" <salyzyn@...gle.com>
CC:     Subhash Jadavani <subhashj@...eaurora.org>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Pedro Sousa <pedrom.sousa@...opsys.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Stanley Chu <stanley.chu@...iatek.com>,
        Bean Huo <beanhuo@...ron.com>,
        Tomas Winkler <tomas.winkler@...el.com>,
        Venkat Gopalakrishnan <venkatg@...eaurora.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v5 7/7] scsi: ufs: Fix error handing during hibern8 enter

 
> 
> From: Subhash Jadavani <subhashj@...eaurora.org>
> 
> During clock gating (ufshcd_gate_work()), we first put the link hibern8 by
> calling ufshcd_uic_hibern8_enter() and if ufshcd_uic_hibern8_enter() returns
> success (0) then we gate all the clocks.
> Now let’s zoom in to what ufshcd_uic_hibern8_enter() does internally:
> It calls __ufshcd_uic_hibern8_enter() and if failure is encountered, link recovery
> shall put the link back to the highest HS gear and returns success (0) to
> ufshcd_uic_hibern8_enter() which is the issue as link is still in active state due to
> recovery!
> Now ufshcd_uic_hibern8_enter() returns success to ufshcd_gate_work() and
> hence it goes ahead with gating the UFS clock while link is still in active state
> hence I believe controller would raise UIC error interrupts. But when we service
> the interrupt, clocks might have already been disabled!
> 
> This change fixes for this by returning failure from
> __ufshcd_uic_hibern8_enter() if recovery succeeds as link is still not in hibern8,
> upon receiving the error ufshcd_hibern8_enter() would initiate retry to put the
> link state back into hibern8.
> 
> Signed-off-by: Subhash Jadavani <subhashj@...eaurora.org>
> Signed-off-by: Can Guo <cang@...eaurora.org>
Reviewed-by: Avri Altman <avri.altman@....com>