linux-kernel - [PATCH v3 1/5] scsi: ufs-mediatek: Fix imprecise waiting time for ref-clk control

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Date:   Mon, 1 Jun 2020 18:46:42 +0800
From:   Stanley Chu <stanley.chu@...iatek.com>
To:     <linux-scsi@...r.kernel.org>, <martin.petersen@...cle.com>,
        <avri.altman@....com>, <alim.akhtar@...sung.com>,
        <jejb@...ux.ibm.com>
CC:     <beanhuo@...ron.com>, <asutoshd@...eaurora.org>,
        <cang@...eaurora.org>, <matthias.bgg@...il.com>,
        <bvanassche@....org>, <linux-mediatek@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <kuohong.wang@...iatek.com>,
        <peter.wang@...iatek.com>, <chun-hung.wu@...iatek.com>,
        <andy.teng@...iatek.com>, <cc.chou@...iatek.com>,
        <chaotian.jing@...iatek.com>,
        Stanley Chu <stanley.chu@...iatek.com>
Subject: [PATCH v3 1/5] scsi: ufs-mediatek: Fix imprecise waiting time for ref-clk control

Currently ref-clk control timeout is implemented by Jiffies. However
jiffies is not accurate enough thus "false timeout" may happen.

Use more accurate delay mechanism instead, for example, ktime.

Signed-off-by: Stanley Chu <stanley.chu@...iatek.com>
Reviewed-by: Andy Teng <andy.teng@...iatek.com>
Reviewed-by: Avri Altman <avri.altman@....com>
---
 drivers/scsi/ufs/ufs-mediatek.c | 7 ++++---
 drivers/scsi/ufs/ufs-mediatek.h | 2 +-
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/scsi/ufs/ufs-mediatek.c b/drivers/scsi/ufs/ufs-mediatek.c
index d56ce8d97d4e..523ee5573921 100644
--- a/drivers/scsi/ufs/ufs-mediatek.c
+++ b/drivers/scsi/ufs/ufs-mediatek.c
@@ -120,7 +120,7 @@ static int ufs_mtk_setup_ref_clk(struct ufs_hba *hba, bool on)
 {
 	struct ufs_mtk_host *host = ufshcd_get_variant(hba);
 	struct arm_smccc_res res;
-	unsigned long timeout;
+	ktime_t timeout, time_checked;
 	u32 value;
 
 	if (host->ref_clk_enabled == on)
@@ -135,8 +135,9 @@ static int ufs_mtk_setup_ref_clk(struct ufs_hba *hba, bool on)
 	}
 
 	/* Wait for ack */
-	timeout = jiffies + msecs_to_jiffies(REFCLK_REQ_TIMEOUT_MS);
+	timeout = ktime_add_us(ktime_get(), REFCLK_REQ_TIMEOUT_US);
 	do {
+		time_checked = ktime_get();
 		value = ufshcd_readl(hba, REG_UFS_REFCLK_CTRL);
 
 		/* Wait until ack bit equals to req bit */
@@ -144,7 +145,7 @@ static int ufs_mtk_setup_ref_clk(struct ufs_hba *hba, bool on)
 			goto out;
 
 		usleep_range(100, 200);
-	} while (time_before(jiffies, timeout));
+	} while (ktime_before(time_checked, timeout));
 
 	dev_err(hba->dev, "missing ack of refclk req, reg: 0x%x\n", value);
 
diff --git a/drivers/scsi/ufs/ufs-mediatek.h b/drivers/scsi/ufs/ufs-mediatek.h
index 5bbd3e9cbae2..fc42dcbfd800 100644
--- a/drivers/scsi/ufs/ufs-mediatek.h
+++ b/drivers/scsi/ufs/ufs-mediatek.h
@@ -28,7 +28,7 @@
 #define REFCLK_REQUEST              BIT(0)
 #define REFCLK_ACK                  BIT(1)
 
-#define REFCLK_REQ_TIMEOUT_MS       3
+#define REFCLK_REQ_TIMEOUT_US       3000
 
 /*
  * Vendor specific pre-defined parameters
-- 
2.18.0