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drivers: libata-core: Use usleep_range() instead of msleep() for short sleeps (<20 ms) 

Since msleep() may sleep longer than intended time for values less
than 20ms, this patch allows the use of usleep_range for waits less
that 20ms. usleep_range is a finer precision implementation of
msleep and is designed to be a drop-in replacement for udelay
where a precise sleep/busy-wait is unnecessary.

More details can be found at http://lkml.org/lkml/2007/8/3/250
and in Documentation/timers/timers-howto.txt.

This change has been done to improve the performace in PIO6 mode
which is used by viking flash.

Cc: xe-kernel@external.cisco.com
Signed-off-by: Anil Veliyankara Madam <aveliyan@cisco.com>
Signed-off-by: Shikha Jain <shikjain@cisco.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
hifive-unleashed-5.1
Anil Veliyankara Madam 2016-01-07 21:18:52 -08:00 committed by Tejun Heo
parent 427cc61a44
commit 848c392086
1 changed files with 7 additions and 1 deletions
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8
drivers/ata/libata-core.c
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@ -50,6 +50,7 @@
#include <linux/blkdev.h>
#include <linux/delay.h>
#include <linux/timer.h>
#include <linux/time.h>
#include <linux/interrupt.h>
#include <linux/completion.h>
#include <linux/suspend.h>
@ -6704,7 +6705,12 @@ void ata_msleep(struct ata_port *ap, unsigned int msecs)
if (owns_eh)
ata_eh_release(ap);
msleep(msecs);
if (msecs < 20) {
unsigned long usecs = msecs * USEC_PER_MSEC;
usleep_range(usecs, usecs + 50);
} else {
msleep(msecs);
}
if (owns_eh)
ata_eh_acquire(ap);