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[PATCH] ieee1394: fix calculation of csr->expire 

This variant of calculate_expire() is more correct and easier to read.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: Ben Collins <bcollins@ubuntu.com>
This commit is contained in:
Stefan Richter 2006-07-03 12:01:59 -04:00 committed by Ben Collins
parent 31a379e106
commit f0cbefe63c
1 changed files with 10 additions and 21 deletions
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31
drivers/ieee1394/csr.c
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@ -17,11 +17,13 @@
*
*/
#include <linux/string.h>
#include <linux/jiffies.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/param.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include "csr1212.h"
#include "ieee1394_types.h"
@ -149,31 +151,18 @@ static void host_reset(struct hpsb_host *host)
/*
* HI == seconds (bits 0:2)
* LO == fraction units of 1/8000 of a second, as per 1394 (bits 19:31)
* LO == fractions of a second in units of 125usec (bits 19:31)
*
* Convert to units and then to HZ, for comparison to jiffies.
*
* By default this will end up being 800 units, or 100ms (125usec per
* unit).
*
* NOTE: The spec says 1/8000, but also says we can compute based on 1/8192
* like CSR specifies. Should make our math less complex.
* Convert SPLIT_TIMEOUT to jiffies.
* The default and minimum as per 1394a-2000 clause 8.3.2.2.6 is 100ms.
*/
static inline void calculate_expire(struct csr_control *csr)
{
unsigned long units;
unsigned long usecs =
(csr->split_timeout_hi & 0x07) * USEC_PER_SEC +
(csr->split_timeout_lo >> 19) * 125L;
/* Take the seconds, and convert to units */
units = (unsigned long)(csr->split_timeout_hi & 0x07) << 13;
/* Add in the fractional units */
units += (unsigned long)(csr->split_timeout_lo >> 19);
/* Convert to jiffies */
csr->expire = (unsigned long)(units * HZ) >> 13UL;
/* Just to keep from rounding low */
csr->expire++;
csr->expire = usecs_to_jiffies(usecs > 100000L ? usecs : 100000L);
HPSB_VERBOSE("CSR: setting expire to %lu, HZ=%u", csr->expire, HZ);
}