linux-kernel - RE: [PATCH v4 7/7] scsi: ufs: Fix error handing during hibern8 enter

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Message-ID: <MN2PR04MB699130F410CDE9BFB5815CC0FC710@MN2PR04MB6991.namprd04.prod.outlook.com>
Date:   Thu, 14 Nov 2019 11:06:25 +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 v4 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() which on detecting the LINERESET,
> initiates the full recovery and puts the link back to 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>
> ---
>  drivers/scsi/ufs/ufshcd.c | 19 ++++++++++++++-----
>  1 file changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c index
> 7a5a904..934c27a 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -3891,15 +3891,24 @@ static int __ufshcd_uic_hibern8_enter(struct
> ufs_hba *hba)
>                              ktime_to_us(ktime_sub(ktime_get(), start)), ret);
> 
>         if (ret) {
> +               int err;
> +
>                 dev_err(hba->dev, "%s: hibern8 enter failed. ret = %d\n",
>                         __func__, ret);
> 
>                 /*
> -                * If link recovery fails then return error so that caller
> -                * don't retry the hibern8 enter again.
> +                * If link recovery fails then return error code (-ENOLINK)
> +                * returned ufshcd_link_recovery().
> +                * If link recovery succeeds then return -EAGAIN to attempt
> +                * hibern8 enter retry again.
You no longer returning -ENOLINK, and either way retrying, regardless of the error code.
Better check that the commit log is still telling the correct story, taking into consideration all those recent fixes and all.

>                  */
> -               if (ufshcd_link_recovery(hba))
> -                       ret = -ENOLINK;
> +               err = ufshcd_link_recovery(hba);
> +               if (err) {
> +                       dev_err(hba->dev, "%s: link recovery failed", __func__);
> +                       ret = err;
> +               } else {
> +                       ret = -EAGAIN;
> +               }
>         } else
>                 ufshcd_vops_hibern8_notify(hba, UIC_CMD_DME_HIBER_ENTER,
>                                                                 POST_CHANGE); @@ -3913,7 +3922,7 @@
> static int ufshcd_uic_hibern8_enter(struct ufs_hba *hba)
> 
>         for (retries = UIC_HIBERN8_ENTER_RETRIES; retries > 0; retries--) {
>                 ret = __ufshcd_uic_hibern8_enter(hba);
> -               if (!ret || ret == -ENOLINK)
> +               if (!ret)
>                         goto out;
>         }
>  out:
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project