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* [PATCH] mtd: dataflash: replace msleep with usleep_range
@ 2018-04-18  9:26 Luca Ellero
  2018-04-26 18:03 ` Boris Brezillon
  0 siblings, 1 reply; 2+ messages in thread
From: Luca Ellero @ 2018-04-18  9:26 UTC (permalink / raw)
  Cc: Luca Ellero, David Woodhouse, Brian Norris, Boris Brezillon,
	Marek Vasut, Richard Weinberger, Andrey Smirnov, Miquel Raynal,
	linux-mtd, linux-kernel

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@brickedbrain.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

^ permalink raw reply	[flat|nested] 2+ messages in thread

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2018-04-18  9:26 [PATCH] mtd: dataflash: replace msleep with usleep_range Luca Ellero
2018-04-26 18:03 ` Boris Brezillon

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