[CPUFREQ] Sync p4-clockmod MSR access across logical CPUs.

As noted and debugged by Rutger Nijlunsing and verified in section 13.15.3 of Intel's
IA32 Intel Architecture Software Developer's Manual, Volume 3, the p4-clockmod
msr needs to be set to the same value on all logical CPUs ("siblings") to
function "properly".

This patch implements this, and uses cpufreq_p4_get instead of a local copy in
cpufreq_p4_setdc. The latter function now only does the actual setting, all
other (notification, verification and set_cpus_allowed()) stuff is done in
cpufreq_p4_target.

diff --git a/arch/i386/kernel/cpu/cpufreq/p4-clockmod.c b/arch/i386/kernel/cpu/cpufreq/p4-clockmod.c
index 75428239386657e59e6b0ca8d6b2117b440d194d..b521aa70a4e3431c641cc9dc814f883e47addba5 100644 (file)
--- a/arch/i386/kernel/cpu/cpufreq/p4-clockmod.c
+++ b/arch/i386/kernel/cpu/cpufreq/p4-clockmod.c
@@ -52,55 +52,15 @@ enum {
 static int has_N44_O17_errata[NR_CPUS];
 static unsigned int stock_freq;
 static struct cpufreq_driver p4clockmod_driver;
+static unsigned int cpufreq_p4_get(unsigned int cpu);
 
 static int cpufreq_p4_setdc(unsigned int cpu, unsigned int newstate)
 {
        u32 l, h;
-       cpumask_t cpus_allowed, affected_cpu_map;
-       struct cpufreq_freqs freqs;
-       int j;
 
-       if (!cpu_online(cpu) || (newstate > DC_DISABLE) || 
-               (newstate == DC_RESV))
+       if (!cpu_online(cpu) || (newstate > DC_DISABLE) || (newstate == DC_RESV))
                return -EINVAL;
 
-       /* switch to physical CPU where state is to be changed*/
-       cpus_allowed = current->cpus_allowed;
-
-       /* only run on CPU to be set, or on its sibling */
-#ifdef CONFIG_SMP
-       affected_cpu_map = cpu_sibling_map[cpu];
-#else
-       affected_cpu_map = cpumask_of_cpu(cpu);
-#endif
-       set_cpus_allowed(current, affected_cpu_map);
-        BUG_ON(!cpu_isset(smp_processor_id(), affected_cpu_map));
-
-       /* get current state */
-       rdmsr(MSR_IA32_THERM_CONTROL, l, h);
-       if (l & 0x10) {
-               l = l >> 1;
-               l &= 0x7;
-       } else
-               l = DC_DISABLE;
-       
-       if (l == newstate) {
-               set_cpus_allowed(current, cpus_allowed);
-               return 0;
-       } else if (l == DC_RESV) {
-               printk(KERN_ERR PFX "BIG FAT WARNING: currently in invalid setting\n");
-       }
-
-       /* notifiers */
-       freqs.old = stock_freq * l / 8;
-       freqs.new = stock_freq * newstate / 8;
-       for_each_cpu(j) {
-               if (cpu_isset(j, affected_cpu_map)) {
-                       freqs.cpu = j;
-                       cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
-               }
-       }
-
        rdmsr(MSR_IA32_THERM_STATUS, l, h);
 #if 0
        if (l & 0x01)
@@ -126,16 +86,6 @@ static int cpufreq_p4_setdc(unsigned int cpu, unsigned int newstate)
                wrmsr(MSR_IA32_THERM_CONTROL, l, h);
        }
 
-       set_cpus_allowed(current, cpus_allowed);
-
-       /* notifiers */
-       for_each_cpu(j) {
-               if (cpu_isset(j, affected_cpu_map)) {
-                       freqs.cpu = j;
-                       cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
-               }
-       }
-
        return 0;
 }
 
@@ -159,11 +109,59 @@ static int cpufreq_p4_target(struct cpufreq_policy *policy,
                             unsigned int relation)
 {
        unsigned int    newstate = DC_RESV;
+       struct cpufreq_freqs freqs;
+       cpumask_t cpus_allowed, affected_cpu_map;
+       int i;
 
        if (cpufreq_frequency_table_target(policy, &p4clockmod_table[0], target_freq, relation, &newstate))
                return -EINVAL;
 
-       cpufreq_p4_setdc(policy->cpu, p4clockmod_table[newstate].index);
+       freqs.old = cpufreq_p4_get(policy->cpu);
+       freqs.new = stock_freq * p4clockmod_table[newstate].index / 8;
+
+       if (freqs.new == freqs.old)
+               return 0;
+
+       /* switch to physical CPU where state is to be changed*/
+       cpus_allowed = current->cpus_allowed;
+
+       /* only run on CPU to be set, or on its sibling */
+#ifdef CONFIG_SMP
+       affected_cpu_map = cpu_sibling_map[policy->cpu];
+#else
+       affected_cpu_map = cpumask_of_cpu(policy->cpu);
+#endif
+
+       /* notifiers */
+       for_each_cpu(i) {
+               if (cpu_isset(i, affected_cpu_map)) {
+                       freqs.cpu = i;
+                       cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
+               }
+       }
+
+       /* run on each logical CPU, see section 13.15.3 of IA32 Intel Architecture Software
+        * Developer's Manual, Volume 3 
+        */
+       for_each_cpu(i) {
+               if (cpu_isset(i, affected_cpu_map)) {
+                       cpumask_t this_cpu = cpumask_of_cpu(i);
+
+                       set_cpus_allowed(current, this_cpu);
+                       BUG_ON(smp_processor_id() != i);
+
+                       cpufreq_p4_setdc(i, p4clockmod_table[newstate].index);
+               }
+       }
+       set_cpus_allowed(current, cpus_allowed);
+
+       /* notifiers */
+       for_each_cpu(i) {
+               if (cpu_isset(i, affected_cpu_map)) {
+                       freqs.cpu = i;
+                       cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
+               }
+       }
 
        return 0;
 }
@@ -271,13 +269,9 @@ static unsigned int cpufreq_p4_get(unsigned int cpu)
        cpumask_t cpus_allowed, affected_cpu_map;
        u32 l, h;
 
-       /* only run on CPU to be set, or on its sibling */
        cpus_allowed = current->cpus_allowed;
-#ifdef CONFIG_SMP
-        affected_cpu_map = cpu_sibling_map[cpu];
-#else
         affected_cpu_map = cpumask_of_cpu(cpu);
-#endif
+
        set_cpus_allowed(current, affected_cpu_map);
         BUG_ON(!cpu_isset(smp_processor_id(), affected_cpu_map));