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[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>
This commit is contained in:
Dave Jones 2005-10-21 17:21:03 -04:00 committed by Linus Torvalds
parent 3078fcc1d1
commit 0213df7431
1 changed files with 19 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

30
arch/i386/kernel/cpu/cpufreq/powernow-k8.c
View File

@ -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 @@ static int query_current_values_with_pending_wait(struct powernow_k8_data *data)
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 @@ static int write_new_fid(struct powernow_k8_data *data, u32 fid)
{
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 @@ static int write_new_fid(struct powernow_k8_data *data, u32 fid)
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 @@ static int write_new_vid(struct powernow_k8_data *data, u32 vid)
{
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 @@ static int write_new_vid(struct powernow_k8_data *data, u32 vid)
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",