[PATCH v3] scsi: ufs: Fix possible infinite loop in ufshcd_hold

* [PATCH v3] scsi: ufs: Fix possible infinite loop in ufshcd_hold
@ 2020-08-09  5:07 Stanley Chu
  2020-08-18  3:12 ` Martin K. Petersen
  0 siblings, 1 reply; 2+ messages in thread
From: Stanley Chu @ 2020-08-09  5:07 UTC (permalink / raw)
  To: linux-scsi, martin.petersen, avri.altman, alim.akhtar, jejb, bvanassche
  Cc: beanhuo, asutoshd, cang, matthias.bgg, linux-mediatek,
	linux-arm-kernel, linux-kernel, kuohong.wang, peter.wang,
	chun-hung.wu, andy.teng, chaotian.jing, cc.chou, Stanley Chu

In ufshcd_suspend(), after clk-gating is suspended and link is set
as Hibern8 state, ufshcd_hold() is still possibly invoked before
ufshcd_suspend() returns. For example, MediaTek's suspend vops may
issue UIC commands which would call ufshcd_hold() during the command
issuing flow.

Now if UFSHCD_CAP_HIBERN8_WITH_CLK_GATING capability is enabled,
then ufshcd_hold() may enter infinite loops because there is no
clk-ungating work scheduled or pending. In this case, ufshcd_hold()
shall just bypass, and keep the link as Hibern8 state.

Co-Developed-by: Andy Teng <andy.teng@mediatek.com>
Reviewed-by: Avri Altman <avri.altman@wdc.com>
Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
---
Changes since v2:
    - Rebase to the latest Martin's queue branch
    - Add missing Reviewed tag since Avri's letter is not showing up in LKML and Patchwork
---
 drivers/scsi/ufs/ufshcd.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 307622284239..b4f948027b3e 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1561,6 +1561,7 @@ static void ufshcd_ungate_work(struct work_struct *work)
 int ufshcd_hold(struct ufs_hba *hba, bool async)
 {
 	int rc = 0;
+	bool flush_result;
 	unsigned long flags;
 
 	if (!ufshcd_is_clkgating_allowed(hba))
@@ -1592,7 +1593,9 @@ int ufshcd_hold(struct ufs_hba *hba, bool async)
 				break;
 			}
 			spin_unlock_irqrestore(hba->host->host_lock, flags);
-			flush_work(&hba->clk_gating.ungate_work);
+			flush_result = flush_work(&hba->clk_gating.ungate_work);
+			if (hba->clk_gating.is_suspended && !flush_result)
+				goto out;
 			spin_lock_irqsave(hba->host->host_lock, flags);
 			goto start;
 		}
-- 
2.18.0

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