[PATCH] ppc32: fix cpu voltage change delay

This patch fixes a problem where my new powerbook would sometimes hang or
crash when changing CPU speed.  We had schedule_timeout(HZ/1000) in there,
intended to provide a delay of one millisecond.  However, even with
HZ=1000, it was (I believe) only waiting for the next jiffy before
proceeding, which could be less than a millisecond.  Changing the code to
use msleep, and specifying a time of 1 jiffy + 1ms has fixed the problem.
(When I looked at the msleep code, it appeared to me that msleep(1) with
HZ=1000 would sleep for between 0 and 1ms.)

Ben also asked me to remove the code that changes the AACK delay enable,
after looking in the Darwin sources and seeing that Darwin does not change
this in its corresponding code.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/arch/ppc/platforms/pmac_cpufreq.c b/arch/ppc/platforms/pmac_cpufreq.c
index b51b37d164e7b6250bb4db7d169308460bcfcf7b..536d3829b092da14a294ad2d469a2243ec11b585 100644 (file)
--- a/arch/ppc/platforms/pmac_cpufreq.c
+++ b/arch/ppc/platforms/pmac_cpufreq.c
@@ -140,11 +140,8 @@ static int __pmac dfs_set_cpu_speed(int low_speed)
        if (low_speed == 0) {
                /* ramping up, set voltage first */
                pmac_call_feature(PMAC_FTR_WRITE_GPIO, NULL, voltage_gpio, 0x05);
-               set_current_state(TASK_UNINTERRUPTIBLE);
-               schedule_timeout(HZ/1000);
-       } else {
-               /* ramping down, enable aack delay first */
-               pmac_call_feature(PMAC_FTR_AACK_DELAY_ENABLE, NULL, 1, 0);
+               /* Make sure we sleep for at least 1ms */
+               msleep(1 + jiffies_to_msecs(1));
        }
 
        /* set frequency */
@@ -153,11 +150,7 @@ static int __pmac dfs_set_cpu_speed(int low_speed)
        if (low_speed == 1) {
                /* ramping down, set voltage last */
                pmac_call_feature(PMAC_FTR_WRITE_GPIO, NULL, voltage_gpio, 0x04);
-               set_current_state(TASK_UNINTERRUPTIBLE);
-               schedule_timeout(HZ/1000);
-       } else {
-               /* ramping up, disable aack delay last */
-               pmac_call_feature(PMAC_FTR_AACK_DELAY_ENABLE, NULL, 0, 0);
+               msleep(1 + jiffies_to_msecs(1));
        }
 
        return 0;