linux-kernel - [PATCH 7/7] scsi: ufs-qcom: Delay specific time before gate ref clk

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Message-Id: <1581123030-12023-8-git-send-email-cang@codeaurora.org>
Date:   Fri,  7 Feb 2020 16:50:29 -0800
From:   Can Guo <cang@...eaurora.org>
To:     asutoshd@...eaurora.org, nguyenb@...eaurora.org,
        hongwus@...eaurora.org, rnayak@...eaurora.org,
        linux-scsi@...r.kernel.org, kernel-team@...roid.com,
        saravanak@...gle.com, salyzyn@...gle.com, cang@...eaurora.org
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-arm-msm@...r.kernel.org (open list:ARM/QUALCOMM SUPPORT),
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH 7/7] scsi: ufs-qcom: Delay specific time before gate ref clk

After enter hibern8, as UFS JEDEC ver 3.0 requires, a specific gating wait
time is required before disable the device reference clock. If it is not
specified, use the old delay.

Signed-off-by: Can Guo <cang@...eaurora.org>
Reviewed-by: Asutosh Das <asutoshd@...eaurora.org>
Reviewed-by: Hongwu Su <hongwus@...eaurora.org>

diff --git a/drivers/scsi/ufs/ufs-qcom.c b/drivers/scsi/ufs/ufs-qcom.c
index 85d7c17..db14a83 100644
--- a/drivers/scsi/ufs/ufs-qcom.c
+++ b/drivers/scsi/ufs/ufs-qcom.c
@@ -845,11 +845,27 @@ static void ufs_qcom_dev_ref_clk_ctrl(struct ufs_qcom_host *host, bool enable)
 		/*
 		 * If we are here to disable this clock it might be immediately
 		 * after entering into hibern8 in which case we need to make
-		 * sure that device ref_clk is active at least 1us after the
+		 * sure that device ref_clk is active for specific time after
 		 * hibern8 enter.
 		 */
-		if (!enable)
-			udelay(1);
+		if (!enable) {
+			unsigned long gating_wait;
+
+			gating_wait = host->hba->dev_info.clk_gating_wait_us;
+			if (!gating_wait) {
+				udelay(1);
+			} else {
+				/*
+				 * bRefClkGatingWaitTime defines the minimum
+				 * time for which the reference clock is
+				 * required by device during transition from
+				 * HS-MODE to LS-MODE or HIBERN8 state. Give it
+				 * more delay to be on the safe side.
+				 */
+				gating_wait += 10;
+				usleep_range(gating_wait, gating_wait + 10);
+			}
+		}
 
 		writel_relaxed(temp, host->dev_ref_clk_ctrl_mmio);
 
-- 
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