Commit f0cbefe6 authored by Stefan Richter's avatar Stefan Richter Committed by Ben Collins
Browse files

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



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

Signed-off-by: default avatarStefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: default avatarBen Collins <bcollins@ubuntu.com>
parent 31a379e1

drivers/ieee1394/csr.c

+10 −21
Original line number Diff line number Diff line
@@ -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)

 *

 * 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).

 * LO == fractions of a second in units of 125usec (bits 19:31)

 *

 * 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;



	/* 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;

	unsigned long usecs =

		(csr->split_timeout_hi & 0x07) * USEC_PER_SEC +

		(csr->split_timeout_lo >> 19) * 125L;



	/* 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);

}