[PATCH] cpufreq: fix pending powernow timer stuck condition
AMD recently discovered that on some hardware, there is a race condition
possible when a C-state change request goes onto the bus at the same
time as a P-state change request.
Both requests happen, but the southbridge hardware only acknowledges the
C-state change. The PowerNow! driver is then stuck in a loop, waiting
for the P-state change acknowledgement. The driver eventually times
out, but can no longer perform P-state changes.
It turns out the solution is to resend the P-state change, which the
southbridge will acknowledge normally.
Thanks to Johannes Winkelmann for reporting this and testing the fix.
Signed-off-by: Mark Langsdorf <mark.langsdorf@amd.com>
Signed-off-by: Dave Jones <davej@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/i386/kernel/cpu/cpufreq/powernow-k8.c b/arch/i386/kernel/cpu/cpufreq/powernow-k8.c
index ab6e061..ec3a9e3 100644
--- a/arch/i386/kernel/cpu/cpufreq/powernow-k8.c
+++ b/arch/i386/kernel/cpu/cpufreq/powernow-k8.c
@@ -44,7 +44,7 @@
#define PFX "powernow-k8: "
#define BFX PFX "BIOS error: "
-#define VERSION "version 1.50.3"
+#define VERSION "version 1.50.4"
#include "powernow-k8.h"
/* serialize freq changes */
@@ -111,8 +111,8 @@
u32 i = 0;
do {
- if (i++ > 0x1000000) {
- printk(KERN_ERR PFX "detected change pending stuck\n");
+ if (i++ > 10000) {
+ dprintk("detected change pending stuck\n");
return 1;
}
rdmsr(MSR_FIDVID_STATUS, lo, hi);
@@ -159,6 +159,7 @@
{
u32 lo;
u32 savevid = data->currvid;
+ u32 i = 0;
if ((fid & INVALID_FID_MASK) || (data->currvid & INVALID_VID_MASK)) {
printk(KERN_ERR PFX "internal error - overflow on fid write\n");
@@ -170,10 +171,13 @@
dprintk("writing fid 0x%x, lo 0x%x, hi 0x%x\n",
fid, lo, data->plllock * PLL_LOCK_CONVERSION);
- wrmsr(MSR_FIDVID_CTL, lo, data->plllock * PLL_LOCK_CONVERSION);
-
- if (query_current_values_with_pending_wait(data))
- return 1;
+ do {
+ wrmsr(MSR_FIDVID_CTL, lo, data->plllock * PLL_LOCK_CONVERSION);
+ if (i++ > 100) {
+ printk(KERN_ERR PFX "internal error - pending bit very stuck - no further pstate changes possible\n");
+ retrun 1;
+ }
+ } while (query_current_values_with_pending_wait(data));
count_off_irt(data);
@@ -197,6 +201,7 @@
{
u32 lo;
u32 savefid = data->currfid;
+ int i = 0;
if ((data->currfid & INVALID_FID_MASK) || (vid & INVALID_VID_MASK)) {
printk(KERN_ERR PFX "internal error - overflow on vid write\n");
@@ -208,10 +213,13 @@
dprintk("writing vid 0x%x, lo 0x%x, hi 0x%x\n",
vid, lo, STOP_GRANT_5NS);
- wrmsr(MSR_FIDVID_CTL, lo, STOP_GRANT_5NS);
-
- if (query_current_values_with_pending_wait(data))
- return 1;
+ do {
+ wrmsr(MSR_FIDVID_CTL, lo, STOP_GRANT_5NS);
+ if (i++ > 100) {
+ printk(KERN_ERR PFX "internal error - pending bit very stuck - no further pstate changes possible\n");
+ return 1;
+ }
+ } while (query_current_values_with_pending_wait(data));
if (savefid != data->currfid) {
printk(KERN_ERR PFX "fid changed on vid trans, old 0x%x new 0x%x\n",