linux-kernel - [PATCH v4 5/5] scsi: ufs: fix clkgating on/off correctly

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Date:   Mon, 26 Oct 2020 12:51:24 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
        kernel-team@...roid.com
Cc:     cang@...eaurora.org, alim.akhtar@...sung.com, avri.altman@....com,
        bvanassche@....org, Jaegeuk Kim <jaegeuk@...nel.org>,
        Asutosh Das <asutoshd@...eaurora.org>
Subject: [PATCH v4 5/5] scsi: ufs: fix clkgating on/off correctly

The below call stack prevents clk_gating at every IO 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 a work to deal with a potential racy 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.

Fixes: 7252a3603015 ("scsi: ufs: Avoid busy-waiting by eliminating tag conflicts")
Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
Reviewed-by: Asutosh Das <asutoshd@...eaurora.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 b8a54d09e750..86c8dee01ca9 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1746,7 +1746,7 @@ 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;
-- 
2.29.0.rc1.297.gfa9743e501-goog