linux-kernel - [PATCH 5.10 166/717] scsi: ufs: Fix clkgating on/off

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Date:   Mon, 28 Dec 2020 13:42:44 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Asutosh Das <asutoshd@...eaurora.org>,
        Can Guo <cang@...eaurora.org>,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.10 166/717] scsi: ufs: Fix clkgating on/off

From: Jaegeuk Kim <jaegeuk@...nel.org>

[ Upstream commit 8eb456be75af7e5a7ac0cd223eaa198cf7ee2ac1 ]

The following call stack prevents clk_gating at every I/O completion.  We
can remove the condition, ufshcd_any_tag_in_use(), since clkgating_work
will check it again.

ufshcd_complete_requests(struct ufs_hba *hba)
  ufshcd_transfer_req_compl()
    __ufshcd_transfer_req_compl()
      __ufshcd_release(hba)
        if (ufshcd_any_tag_in_use() == 1)
           return;
  ufshcd_tmc_handler(hba);
    blk_mq_tagset_busy_iter();

Note that this still requires work to deal with a potential race condition
when user sets clkgating.delay_ms to very small value. That can cause
preventing clkgating by the check of ufshcd_any_tag_in_use() in gate_work.

Link: https://lore.kernel.org/r/20201117165839.1643377-7-jaegeuk@kernel.org
Fixes: 7252a3603015 ("scsi: ufs: Avoid busy-waiting by eliminating tag conflicts")
Reviewed-by: Asutosh Das <asutoshd@...eaurora.org>
Reviewed-by: Can Guo <cang@...eaurora.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/scsi/ufs/ufshcd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 1ad7d6c130f5b..911aba3e7675c 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1751,7 +1751,7 @@ static void __ufshcd_release(struct ufs_hba *hba)
 
 	if (hba->clk_gating.active_reqs || hba->clk_gating.is_suspended ||
 	    hba->ufshcd_state != UFSHCD_STATE_OPERATIONAL ||
-	    ufshcd_any_tag_in_use(hba) || hba->outstanding_tasks ||
+	    hba->outstanding_tasks ||
 	    hba->active_uic_cmd || hba->uic_async_done ||
 	    hba->clk_gating.state == CLKS_OFF)
 		return;
-- 
2.27.0