Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org,
        kernel-team@android.com
Cc:     cang@codeaurora.org, alim.akhtar@samsung.com, avri.altman@wdc.com,
        bvanassche@acm.org, Jaegeuk Kim <jaegeuk@google.com>
Subject: [PATCH v4 1/5] scsi: ufs: atomic update for clkgating_enable
Date:   Mon, 26 Oct 2020 12:51:20 -0700
Message-Id: <20201026195124.363096-2-jaegeuk@kernel.org>
In-Reply-To: <20201026195124.363096-1-jaegeuk@kernel.org>
References: <20201026195124.363096-1-jaegeuk@kernel.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

From: Jaegeuk Kim <jaegeuk@google.com>

When giving a stress test which enables/disables clkgating, we hit device
timeout sometimes. This patch avoids subtle racy condition to address it.

Note that, this requires a patch to address the device stuck by REQ_CLKS_OFF in
__ufshcd_release().

The fix is "scsi: ufs: avoid to call REQ_CLKS_OFF to CLKS_OFF".

Signed-off-by: Jaegeuk Kim <jaegeuk@google.com>
---
 drivers/scsi/ufs/ufshcd.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index cc8d5f0c3fdc..6c9269bffcbd 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1808,19 +1808,19 @@ static ssize_t ufshcd_clkgate_enable_store(struct device *dev,
 		return -EINVAL;
 
 	value = !!value;
+
+	spin_lock_irqsave(hba->host->host_lock, flags);
 	if (value == hba->clk_gating.is_enabled)
 		goto out;
 
-	if (value) {
-		ufshcd_release(hba);
-	} else {
-		spin_lock_irqsave(hba->host->host_lock, flags);
+	if (value)
+		__ufshcd_release(hba);
+	else
 		hba->clk_gating.active_reqs++;
-		spin_unlock_irqrestore(hba->host->host_lock, flags);
-	}
 
 	hba->clk_gating.is_enabled = value;
 out:
+	spin_unlock_irqrestore(hba->host->host_lock, flags);
 	return count;
 }
 
-- 
2.29.0.rc1.297.gfa9743e501-goog