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

From: Stanley Chu
Date: Sun Aug 09 2020 - 01:15:19 EST

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@xxxxxxxxxxxx>
Reviewed-by: Avri Altman <avri.altman@xxxxxxx>
Signed-off-by: Stanley Chu <stanley.chu@xxxxxxxxxxxx>
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)
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;