[PATCH] Allow all Opteron processors to change pstate at sametime
From: Mark Langsdorf
Date: Thu Jul 06 2006 - 16:30:17 EST
The current generation of Opteron processors do not provide a frequency
independent TSC. This causes wild gettimeofday skew on systems that
enable cpufreq while using TSC as a gtod source.
This patch provides a workaround by changing all processors to the same
frequency at the same time, so that the TSC on each processor never
increments at a different rate than the TSC on another processor.
the "powernow-k8.tscsync=1" options enables simeltameous transitions.
Other options are necessary to force the use of TSC as a gtod source.
This patch should apply cleanly to the 2.6.18-rc1 kernel.
-Mark Langsdorf
AMD, Inc.
signed-off-by: Mark Langsdorf <mark.langsdorf@xxxxxxx>
--- linux-mm2-2.6.17-rc6/arch/i386/kernel/cpu/cpufreq/powernow-k8.c.old 2006-06-12 12:22:06.000000000 -0500
+++ linux-mm2-2.6.17-rc6/arch/i386/kernel/cpu/cpufreq/powernow-k8.c 2006-06-13 15:43:39.000000000 -0500
@@ -46,13 +46,15 @@
#define PFX "powernow-k8: "
#define BFX PFX "BIOS error: "
-#define VERSION "version 2.00.00"
+#define VERSION "version 2.10.00"
#include "powernow-k8.h"
/* serialize freq changes */
static DEFINE_MUTEX(fidvid_mutex);
static struct powernow_k8_data *powernow_data[NR_CPUS];
+static int *req_state = NULL;
+static int tscsync __initdata = 0;
static int cpu_family = CPU_OPTERON;
@@ -205,6 +207,17 @@ static int write_new_fid(struct powernow
dprintk("writing fid 0x%x, lo 0x%x, hi 0x%x\n",
fid, lo, data->plllock * PLL_LOCK_CONVERSION);
+ if (tscsync) {
+ int i;
+ cpumask_t oldmask = current->cpus_allowed;
+ for_each_online_cpu(i) {
+ set_cpus_allowed(current, cpumask_of_cpu(i));
+ schedule();
+ wrmsr(MSR_FIDVID_CTL, lo & ~MSR_C_LO_INIT_FID_VID, data->plllock * PLL_LOCK_CONVERSION);
+ }
+ set_cpus_allowed(current, oldmask);
+ schedule();
+ }
do {
wrmsr(MSR_FIDVID_CTL, lo, data->plllock * PLL_LOCK_CONVERSION);
if (i++ > 100) {
@@ -247,6 +260,17 @@ static int write_new_vid(struct powernow
dprintk("writing vid 0x%x, lo 0x%x, hi 0x%x\n",
vid, lo, STOP_GRANT_5NS);
+ if (tscsync) {
+ int i;
+ cpumask_t oldmask = current->cpus_allowed;
+ for_each_online_cpu(i) {
+ set_cpus_allowed(current, cpumask_of_cpu(i));
+ schedule();
+ wrmsr(MSR_FIDVID_CTL, lo & ~MSR_C_LO_INIT_FID_VID, STOP_GRANT_5NS);
+ }
+ set_cpus_allowed(current, oldmask);
+ schedule();
+ }
do {
wrmsr(MSR_FIDVID_CTL, lo, STOP_GRANT_5NS);
if (i++ > 100) {
@@ -386,7 +410,8 @@ static int core_frequency_transition(str
}
if (data->currfid == reqfid) {
- printk(KERN_ERR PFX "ph2 null fid transition 0x%x\n", data->currfid);
+ if (!tscsync)
+ printk(KERN_ERR PFX "ph2 null fid transition 0x%x\n", data->currfid);
return 0;
}
@@ -960,9 +985,21 @@ static int transition_frequency_fidvid(s
u32 vid = 0;
int res, i;
struct cpufreq_freqs freqs;
+ cpumask_t changing_cores;
dprintk("cpu %d transition to index %u\n", smp_processor_id(), index);
+ /* if all processors are transitioning in step, find the highest
+ * current state and go to that
+ */
+
+ if (tscsync && req_state) {
+ req_state[smp_processor_id()] = index;
+ for_each_online_cpu(i)
+ if (req_state[i] < index)
+ index = req_state[i];
+ }
+
/* fid/vid correctness check for k8 */
/* fid are the lower 8 bits of the index we stored into
* the cpufreq frequency table in find_psb_table, vid
@@ -983,6 +1020,8 @@ static int transition_frequency_fidvid(s
}
if ((fid < HI_FID_TABLE_BOTTOM) && (data->currfid < HI_FID_TABLE_BOTTOM)) {
+ if (tscsync && (data->currfid == fid))
+ return 0;
printk(KERN_ERR PFX
"ignoring illegal change in lo freq table-%x to 0x%x\n",
data->currfid, fid);
@@ -994,7 +1033,11 @@ static int transition_frequency_fidvid(s
freqs.old = find_khz_freq_from_fid(data->currfid);
freqs.new = find_khz_freq_from_fid(fid);
- for_each_cpu_mask(i, *(data->available_cores)) {
+ if (tscsync)
+ changing_cores = cpu_online_map;
+ else
+ changing_cores = *(data->available_cores);
+ for_each_cpu_mask(i, changing_cores) {
freqs.cpu = i;
cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
}
@@ -1002,10 +1045,16 @@ static int transition_frequency_fidvid(s
res = transition_fid_vid(data, fid, vid);
freqs.new = find_khz_freq_from_fid(data->currfid);
- for_each_cpu_mask(i, *(data->available_cores)) {
+ for_each_cpu_mask(i, changing_cores) {
freqs.cpu = i;
cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
}
+ if (tscsync)
+ for_each_online_cpu(i)
+ if (powernow_data[i]) {
+ powernow_data[i]->currfid = data->currfid;
+ powernow_data[i]->currvid = data->currvid;
+ }
return res;
}
@@ -1054,7 +1103,7 @@ static int powernowk8_target(struct cpuf
u32 checkfid;
u32 checkvid;
unsigned int newstate;
- int ret = -EIO;
+ int ret = 0;//-EIO;
if (!data)
return -EINVAL;
@@ -1089,7 +1138,7 @@ static int powernowk8_target(struct cpuf
dprintk("targ: curr fid 0x%x, vid 0x%x\n",
data->currfid, data->currvid);
- if ((checkvid != data->currvid) || (checkfid != data->currfid)) {
+ if (!tscsync && ((checkvid != data->currvid) || (checkfid != data->currfid))) {
printk(KERN_INFO PFX
"error - out of sync, fix 0x%x 0x%x, vid 0x%x 0x%x\n",
checkfid, data->currfid, checkvid, data->currvid);
@@ -1100,7 +1149,6 @@ static int powernowk8_target(struct cpuf
goto err_out;
mutex_lock(&fidvid_mutex);
-
powernow_k8_acpi_pst_values(data, newstate);
if (cpu_family)
@@ -1137,6 +1185,32 @@ static int powernowk8_verify(struct cpuf
return cpufreq_frequency_table_verify(pol, data->powernow_table);
}
+/* On an MP system that is transitioning all cores in sync, adjust the
+ * vids for each frequency to the highest. Otherwise, systems made up
+ * of different steppings may fail.
+ */
+static void sync_tables(int curcpu)
+{
+ int j;
+ for (j = 0; j < powernow_data[curcpu]->numps; j++) {
+ int i;
+ int maxvid = 0;
+ for_each_online_cpu(i) {
+ int testvid;
+ if (!powernow_data[i] || !powernow_data[i]->powernow_table)
+ continue;
+ testvid = powernow_data[i]->powernow_table[j].index & 0xff00;
+ if (testvid > maxvid)
+ maxvid = testvid;
+ }
+ for_each_online_cpu(i) {
+ if (!powernow_data[i] || ! powernow_data[i]->powernow_table)
+ continue;
+ powernow_data[i]->powernow_table[j].index &= 0xff;
+ powernow_data[i]->powernow_table[j].index |= maxvid;
+ }
+ }
+}
/* per CPU init entry point to the driver */
static int __cpuinit powernowk8_cpu_init(struct cpufreq_policy *pol)
{
@@ -1200,6 +1274,9 @@ static int __cpuinit powernowk8_cpu_init
if (!cpu_family)
fidvid_msr_init();
+ if (tscsync && (cpu_family == CPU_OPTERON))
+ req_state[pol->cpu] = 0;
+
/* run on any CPU again */
set_cpus_allowed(current, oldmask);
@@ -1241,6 +1318,8 @@ static int __cpuinit powernowk8_cpu_init
powernow_data[pol->cpu] = data;
+ if (tscsync && (cpu_family == CPU_OPTERON))
+ sync_tables(pol->cpu);
return 0;
err_out:
@@ -1323,6 +1402,13 @@ static int __cpuinit powernowk8_init(voi
}
if (supported_cpus == num_online_cpus()) {
+ if (tscsync) {
+ req_state = kzalloc(sizeof(int)*NR_CPUS, GFP_KERNEL);
+ if (!req_state) {
+ printk(KERN_ERR PFX "Unable to allocate memory!\n");
+ return -ENOMEM;
+ }
+ }
printk(KERN_INFO PFX "Found %d %s "
"processors (" VERSION ")\n", supported_cpus,
boot_cpu_data.x86_model_id);
@@ -1337,6 +1423,9 @@ static void __exit powernowk8_exit(void)
{
dprintk("exit\n");
+ if (tscsync)
+ kfree(req_state);
+
cpufreq_unregister_driver(&cpufreq_amd64_driver);
}
@@ -1346,3 +1435,6 @@ MODULE_LICENSE("GPL");
late_initcall(powernowk8_init);
module_exit(powernowk8_exit);
+
+module_param(tscsync, int, 0);
+MODULE_PARM_DESC(tscsync, "enable tsc by synchronizing powernow-k8 changes");