linux-kernel - [PATCH] mtd: dataflash: replace msleep with usleep

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Date:   Wed, 18 Apr 2018 11:26:26 +0200
From:   Luca Ellero <luca.ellero@...ckedbrain.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Luca Ellero <luca.ellero@...ckedbrain.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Boris Brezillon <boris.brezillon@...tlin.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Richard Weinberger <richard@....at>,
        Andrey Smirnov <andrew.smirnov@...il.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] mtd: dataflash: replace msleep with usleep_range

Since msleep is based on jiffies, this 3 ms sleep becomes actually 20 ms.
Worst of all, since this sleep is used in a loop when writing, a single page
write (256 to 1024 bytes) causes 17 ms extra time.
When writing large files (for example u-boot is usually 512 KB) this delay
adds up to minutes.
See Documentation/timers/timers-howto.txt "Why not msleep for (1ms - 20ms)".

Signed-off-by: Luca Ellero <luca.ellero@...ckedbrain.com>
---
 drivers/mtd/devices/mtd_dataflash.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mtd/devices/mtd_dataflash.c b/drivers/mtd/devices/mtd_dataflash.c
index aaaeaae..3a6f450 100644
--- a/drivers/mtd/devices/mtd_dataflash.c
+++ b/drivers/mtd/devices/mtd_dataflash.c
@@ -140,7 +140,7 @@ static int dataflash_waitready(struct spi_device *spi)
 		if (status & (1 << 7))	/* RDY/nBSY */
 			return status;
 
-		msleep(3);
+		usleep_range(3000, 4000);
 	}
 }
 
-- 
2.7.4