linux-kernel - [PATCH v1 6/6] scsi: ufs: Fix error handing during hibern8 enter

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Message-Id: <1572671016-883-7-git-send-email-cang@codeaurora.org>
Date:   Fri,  1 Nov 2019 22:03:36 -0700
From:   Can Guo <cang@...eaurora.org>
To:     asutoshd@...eaurora.org, nguyenb@...eaurora.org,
        rnayak@...eaurora.org, linux-scsi@...r.kernel.org,
        kernel-team@...roid.com, saravanak@...gle.com, salyzyn@...gle.com,
        cang@...eaurora.org
Cc:     Subhash Jadavani <subhashj@...eaurora.org>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....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>,
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v1 6/6] 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 c9ef2dd..1201578 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.
 		 */
-		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:
-- 
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