linux-kernel - [PATCH v1] scsi: ufs: change msleep to usleep

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Message-ID: <BN7PR08MB5684BBB44FD0E43501558A20DBCF0@BN7PR08MB5684.namprd08.prod.outlook.com>
Date:   Mon, 15 Jul 2019 11:21:10 +0000
From:   "Bean Huo (beanhuo)" <beanhuo@...ron.com>
To:     Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        Pedro Sousa <pedrom.sousa@...opsys.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>
CC:     "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        Evan Green <evgreen@...omium.org>,
        Stanley Chu <stanley.chu@...iatek.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>
Subject: [PATCH v1] scsi: ufs: change msleep to usleep_range

From: Bean Huo <beanhuo@...ron.com>

This patch is to change msleep() to usleep_range() based on
Documentation/timers/timers-howto.txt. It suggests using
usleep_range() for small msec(1ms - 20ms) since msleep()
will often sleep longer than desired value.

After changing, booting time will be 5ms-10ms faster than before.
I tested this change on two different platforms, one has 5ms faster,
another one is about 10ms. I think this is different on different
platform.

Actually, from UFS host side, 1ms-5ms delay is already sufficient for
its initialization of the local UIC layer.

Fixes: 7a3e97b0dc4b ([SCSI] ufshcd: UFS Host controller driver)
Signed-off-by: Bean Huo <beanhuo@...ron.com>
---
 drivers/scsi/ufs/ufshcd.c | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index a208589426b1..21f7b3b8026c 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -4213,12 +4213,6 @@ static int ufshcd_hba_execute_hce(struct ufs_hba *hba)
 {
 	int retry;
 
-	/*
-	 * msleep of 1 and 5 used in this function might result in msleep(20),
-	 * but it was necessary to send the UFS FPGA to reset mode during
-	 * development and testing of this driver. msleep can be changed to
-	 * mdelay and retry count can be reduced based on the controller.
-	 */
 	if (!ufshcd_is_hba_active(hba))
 		/* change controller state to "reset state" */
 		ufshcd_hba_stop(hba, true);
@@ -4241,7 +4235,7 @@ static int ufshcd_hba_execute_hce(struct ufs_hba *hba)
 	 * instruction might be read back.
 	 * This delay can be changed based on the controller.
 	 */
-	msleep(1);
+	usleep_range(1000, 1100);
 
 	/* wait for the host controller to complete initialization */
 	retry = 10;
@@ -4253,7 +4247,7 @@ static int ufshcd_hba_execute_hce(struct ufs_hba *hba)
 				"Controller enable failed\n");
 			return -EIO;
 		}
-		msleep(5);
+		usleep_range(5000, 5100);
 	}
 
 	/* enable UIC related interrupts */
-- 
2.7.4