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authorMark Langsdorf <mark.langsdorf@amd.com>2009-02-03 11:46:43 -0500
committerDave Jones <davej@redhat.com>2009-02-05 12:25:26 -0500
commit732553e567c2700ba5b9bccc6ec885c75779a94b (patch)
tree1b6d7b2686244908935a1c270c86651e904c5f3f /arch/x86/kernel/cpu/cpufreq
parent1ca3abdb6a4b87246b00292f048acd344325fd12 (diff)
[CPUFREQ] powernow-k8: Get transition latency from ACPI _PSS table
At this time, the PowerNow! driver for K8 uses an experimentally derived formula to calculate transition latency. The value it provides is orders of magnitude too large on modern systems. This patch replaces the formula with ACPI _PSS latency values for more accuracy and better performance. I've tested it on two 2nd generation Opteron systems, a 3rd generation Operton system, and a Turion X2 without seeing any stability problems. Signed-off-by: Mark Langsdorf <mark.langsdorf@amd.com> Signed-off-by: Thomas Renninger <trenn@suse.de> Signed-off-by: Dave Jones <davej@redhat.com>
Diffstat (limited to 'arch/x86/kernel/cpu/cpufreq')
-rw-r--r--arch/x86/kernel/cpu/cpufreq/powernow-k8.c28
1 files changed, 22 insertions, 6 deletions
diff --git a/arch/x86/kernel/cpu/cpufreq/powernow-k8.c b/arch/x86/kernel/cpu/cpufreq/powernow-k8.c
index 5c28b37dea11..fb039cd345d8 100644
--- a/arch/x86/kernel/cpu/cpufreq/powernow-k8.c
+++ b/arch/x86/kernel/cpu/cpufreq/powernow-k8.c
@@ -939,10 +939,25 @@ static void powernow_k8_cpu_exit_acpi(struct powernow_k8_data *data)
939 free_cpumask_var(data->acpi_data.shared_cpu_map); 939 free_cpumask_var(data->acpi_data.shared_cpu_map);
940} 940}
941 941
942static int get_transition_latency(struct powernow_k8_data *data)
943{
944 int max_latency = 0;
945 int i;
946 for (i = 0; i < data->acpi_data.state_count; i++) {
947 int cur_latency = data->acpi_data.states[i].transition_latency
948 + data->acpi_data.states[i].bus_master_latency;
949 if (cur_latency > max_latency)
950 max_latency = cur_latency;
951 }
952 /* value in usecs, needs to be in nanoseconds */
953 return 1000 * max_latency;
954}
955
942#else 956#else
943static int powernow_k8_cpu_init_acpi(struct powernow_k8_data *data) { return -ENODEV; } 957static int powernow_k8_cpu_init_acpi(struct powernow_k8_data *data) { return -ENODEV; }
944static void powernow_k8_cpu_exit_acpi(struct powernow_k8_data *data) { return; } 958static void powernow_k8_cpu_exit_acpi(struct powernow_k8_data *data) { return; }
945static void powernow_k8_acpi_pst_values(struct powernow_k8_data *data, unsigned int index) { return; } 959static void powernow_k8_acpi_pst_values(struct powernow_k8_data *data, unsigned int index) { return; }
960static int get_transition_latency(struct powernow_k8_data *data) { return 0; }
946#endif /* CONFIG_X86_POWERNOW_K8_ACPI */ 961#endif /* CONFIG_X86_POWERNOW_K8_ACPI */
947 962
948/* Take a frequency, and issue the fid/vid transition command */ 963/* Take a frequency, and issue the fid/vid transition command */
@@ -1173,7 +1188,13 @@ static int __cpuinit powernowk8_cpu_init(struct cpufreq_policy *pol)
1173 if (rc) { 1188 if (rc) {
1174 goto err_out; 1189 goto err_out;
1175 } 1190 }
1176 } 1191 /* Take a crude guess here.
1192 * That guess was in microseconds, so multiply with 1000 */
1193 pol->cpuinfo.transition_latency = (
1194 ((data->rvo + 8) * data->vstable * VST_UNITS_20US) +
1195 ((1 << data->irt) * 30)) * 1000;
1196 } else /* ACPI _PSS objects available */
1197 pol->cpuinfo.transition_latency = get_transition_latency(data);
1177 1198
1178 /* only run on specific CPU from here on */ 1199 /* only run on specific CPU from here on */
1179 oldmask = current->cpus_allowed; 1200 oldmask = current->cpus_allowed;
@@ -1204,11 +1225,6 @@ static int __cpuinit powernowk8_cpu_init(struct cpufreq_policy *pol)
1204 cpumask_copy(pol->cpus, &per_cpu(cpu_core_map, pol->cpu)); 1225 cpumask_copy(pol->cpus, &per_cpu(cpu_core_map, pol->cpu));
1205 data->available_cores = pol->cpus; 1226 data->available_cores = pol->cpus;
1206 1227
1207 /* Take a crude guess here.
1208 * That guess was in microseconds, so multiply with 1000 */
1209 pol->cpuinfo.transition_latency = (((data->rvo + 8) * data->vstable * VST_UNITS_20US)
1210 + (3 * (1 << data->irt) * 10)) * 1000;
1211
1212 if (cpu_family == CPU_HW_PSTATE) 1228 if (cpu_family == CPU_HW_PSTATE)
1213 pol->cur = find_khz_freq_from_pstate(data->powernow_table, data->currpstate); 1229 pol->cur = find_khz_freq_from_pstate(data->powernow_table, data->currpstate);
1214 else 1230 else