[PATCH] PPC32: Fix cpu voltage change delay

[Paul Mackerras]

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@xxxxxxxxx>

diff -urN linux-2.5/arch/ppc/platforms/pmac_cpufreq.c pmac-2.5/arch/ppc/platforms/pmac_cpufreq.c
--- linux-2.5/arch/ppc/platforms/pmac_cpufreq.c	2004-09-24 15:23:06.000000000 +1000
+++ pmac-2.5/arch/ppc/platforms/pmac_cpufreq.c	2004-10-10 11:23:43.000000000 +1000
@@ -140,11 +140,8 @@
 	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 @@
 	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;
-
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