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authorMikulas Patocka <mpatocka@redhat.com>2014-04-08 18:04:25 -0400
committerWilly Tarreau <w@1wt.eu>2014-05-19 07:54:26 +0200
commit969d4d2cbfb9f42f40094b0a168de457e8cf3a96 (patch)
tree8addacf7eac7d17a4d737f9e89ed05597b0f838d
parent923a78074bfb799508bea3ca3700ee29da7fc58d (diff)
downloadlinux-linaro-stable-969d4d2cbfb9f42f40094b0a168de457e8cf3a96.tar.gz
powernow-k6: correctly initialize default parameters
commit d82b922a4acc1781d368aceac2f9da43b038cab2 upstream The powernow-k6 driver used to read the initial multiplier from the powernow register. However, there is a problem with this: * If there was a frequency transition before, the multiplier read from the register corresponds to the current multiplier. * If there was no frequency transition since reset, the field in the register always reads as zero, regardless of the current multiplier that is set using switches on the mainboard and that the CPU is running at. The zero value corresponds to multiplier 4.5, so as a consequence, the powernow-k6 driver always assumes multiplier 4.5. For example, if we have 550MHz CPU with bus frequency 100MHz and multiplier 5.5, the powernow-k6 driver thinks that the multiplier is 4.5 and bus frequency is 122MHz. The powernow-k6 driver then sets the multiplier to 4.5, underclocking the CPU to 450MHz, but reports the current frequency as 550MHz. There is no reliable way how to read the initial multiplier. I modified the driver so that it contains a table of known frequencies (based on parameters of existing CPUs and some common overclocking schemes) and sets the multiplier according to the frequency. If the frequency is unknown (because of unusual overclocking or underclocking), the user must supply the bus speed and maximum multiplier as module parameters. This patch should be backported to all stable kernels. If it doesn't apply cleanly, change it, or ask me to change it. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Signed-off-by: Willy Tarreau <w@1wt.eu>
-rw-r--r--arch/x86/kernel/cpu/cpufreq/powernow-k6.c76
1 files changed, 72 insertions, 4 deletions
diff --git a/arch/x86/kernel/cpu/cpufreq/powernow-k6.c b/arch/x86/kernel/cpu/cpufreq/powernow-k6.c
index 9f80a34024f8..2d9161eda69c 100644
--- a/arch/x86/kernel/cpu/cpufreq/powernow-k6.c
+++ b/arch/x86/kernel/cpu/cpufreq/powernow-k6.c
@@ -26,6 +26,14 @@
static unsigned int busfreq; /* FSB, in 10 kHz */
static unsigned int max_multiplier;
+static unsigned int param_busfreq = 0;
+static unsigned int param_max_multiplier = 0;
+
+module_param_named(max_multiplier, param_max_multiplier, uint, S_IRUGO);
+MODULE_PARM_DESC(max_multiplier, "Maximum multiplier (allowed values: 20 30 35 40 45 50 55 60)");
+
+module_param_named(bus_frequency, param_busfreq, uint, S_IRUGO);
+MODULE_PARM_DESC(bus_frequency, "Bus frequency in kHz");
/* Clock ratio multiplied by 10 - see table 27 in AMD#23446 */
static struct cpufreq_frequency_table clock_ratio[] = {
@@ -40,6 +48,27 @@ static struct cpufreq_frequency_table clock_ratio[] = {
{0, CPUFREQ_TABLE_END}
};
+static const struct {
+ unsigned freq;
+ unsigned mult;
+} usual_frequency_table[] = {
+ { 400000, 40 }, // 100 * 4
+ { 450000, 45 }, // 100 * 4.5
+ { 475000, 50 }, // 95 * 5
+ { 500000, 50 }, // 100 * 5
+ { 506250, 45 }, // 112.5 * 4.5
+ { 533500, 55 }, // 97 * 5.5
+ { 550000, 55 }, // 100 * 5.5
+ { 562500, 50 }, // 112.5 * 5
+ { 570000, 60 }, // 95 * 6
+ { 600000, 60 }, // 100 * 6
+ { 618750, 55 }, // 112.5 * 5.5
+ { 660000, 55 }, // 120 * 5.5
+ { 675000, 60 }, // 112.5 * 6
+ { 720000, 60 }, // 120 * 6
+};
+
+#define FREQ_RANGE 3000
/**
* powernow_k6_get_cpu_multiplier - returns the current FSB multiplier
@@ -163,18 +192,57 @@ static int powernow_k6_target(struct cpufreq_policy *policy,
return 0;
}
-
static int powernow_k6_cpu_init(struct cpufreq_policy *policy)
{
unsigned int i, f;
int result;
+ unsigned khz;
if (policy->cpu != 0)
return -ENODEV;
- /* get frequencies */
- max_multiplier = powernow_k6_get_cpu_multiplier();
- busfreq = cpu_khz / max_multiplier;
+ max_multiplier = 0;
+ khz = cpu_khz;
+ for (i = 0; i < ARRAY_SIZE(usual_frequency_table); i++) {
+ if (khz >= usual_frequency_table[i].freq - FREQ_RANGE &&
+ khz <= usual_frequency_table[i].freq + FREQ_RANGE) {
+ khz = usual_frequency_table[i].freq;
+ max_multiplier = usual_frequency_table[i].mult;
+ break;
+ }
+ }
+ if (param_max_multiplier) {
+ for (i = 0; (clock_ratio[i].frequency != CPUFREQ_TABLE_END); i++) {
+ if (clock_ratio[i].index == param_max_multiplier) {
+ max_multiplier = param_max_multiplier;
+ goto have_max_multiplier;
+ }
+ }
+ printk(KERN_ERR "powernow-k6: invalid max_multiplier parameter, valid parameters 20, 30, 35, 40, 45, 50, 55, 60\n");
+ return -EINVAL;
+ }
+
+ if (!max_multiplier) {
+ printk(KERN_WARNING "powernow-k6: unknown frequency %u, cannot determine current multiplier\n", khz);
+ printk(KERN_WARNING "powernow-k6: use module parameters max_multiplier and bus_frequency\n");
+ return -EOPNOTSUPP;
+ }
+
+have_max_multiplier:
+ param_max_multiplier = max_multiplier;
+
+ if (param_busfreq) {
+ if (param_busfreq >= 50000 && param_busfreq <= 150000) {
+ busfreq = param_busfreq / 10;
+ goto have_busfreq;
+ }
+ printk(KERN_ERR "powernow-k6: invalid bus_frequency parameter, allowed range 50000 - 150000 kHz\n");
+ return -EINVAL;
+ }
+
+ busfreq = khz / max_multiplier;
+have_busfreq:
+ param_busfreq = busfreq * 10;
/* table init */
for (i = 0; (clock_ratio[i].frequency != CPUFREQ_TABLE_END); i++) {