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authorViresh Kumar <viresh.kumar@linaro.org>2013-12-03 11:20:46 +0530
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2014-01-06 14:17:25 +0100
commitd3916691c90dfc9f08328d5cef8181e9ea508c55 (patch)
treee32b3422823ef3a64a42c1c72785a169fff20a9c /drivers/cpufreq
parentae6b427132ba39d023e332e7d920e9931ff05313 (diff)
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cpufreq: Make sure CPU is running on a freq from freq-table
Sometimes boot loaders set CPU frequency to a value outside of frequency table present with cpufreq core. In such cases CPU might be unstable if it has to run on that frequency for long duration of time and so its better to set it to a frequency which is specified in freq-table. This also makes cpufreq stats inconsistent as cpufreq-stats would fail to register because current frequency of CPU isn't found in freq-table. Because we don't want this change to affect boot process badly, we go for the next freq which is >= policy->cur ('cur' must be set by now, otherwise we will end up setting freq to lowest of the table as 'cur' is initialized to zero). In case current frequency doesn't match any frequency from freq-table, we throw warnings to user, so that user can get this fixed in their bootloaders or freq-tables. Reported-by: Carlos Hernandez <ceh@ti.com> Reported-and-tested-by: Nishanth Menon <nm@ti.com> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers/cpufreq')
-rw-r--r--drivers/cpufreq/cpufreq.c40
-rw-r--r--drivers/cpufreq/freq_table.c22
2 files changed, 62 insertions, 0 deletions
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index d533c20..3509ca0 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1073,6 +1073,46 @@ static int __cpufreq_add_dev(struct device *dev, struct subsys_interface *sif,
}
}
+ /*
+ * Sometimes boot loaders set CPU frequency to a value outside of
+ * frequency table present with cpufreq core. In such cases CPU might be
+ * unstable if it has to run on that frequency for long duration of time
+ * and so its better to set it to a frequency which is specified in
+ * freq-table. This also makes cpufreq stats inconsistent as
+ * cpufreq-stats would fail to register because current frequency of CPU
+ * isn't found in freq-table.
+ *
+ * Because we don't want this change to effect boot process badly, we go
+ * for the next freq which is >= policy->cur ('cur' must be set by now,
+ * otherwise we will end up setting freq to lowest of the table as 'cur'
+ * is initialized to zero).
+ *
+ * We are passing target-freq as "policy->cur - 1" otherwise
+ * __cpufreq_driver_target() would simply fail, as policy->cur will be
+ * equal to target-freq.
+ */
+ if ((cpufreq_driver->flags & CPUFREQ_NEED_INITIAL_FREQ_CHECK)
+ && has_target()) {
+ /* Are we running at unknown frequency ? */
+ ret = cpufreq_frequency_table_get_index(policy, policy->cur);
+ if (ret == -EINVAL) {
+ /* Warn user and fix it */
+ pr_warn("%s: CPU%d: Running at unlisted freq: %u KHz\n",
+ __func__, policy->cpu, policy->cur);
+ ret = __cpufreq_driver_target(policy, policy->cur - 1,
+ CPUFREQ_RELATION_L);
+
+ /*
+ * Reaching here after boot in a few seconds may not
+ * mean that system will remain stable at "unknown"
+ * frequency for longer duration. Hence, a BUG_ON().
+ */
+ BUG_ON(ret);
+ pr_warn("%s: CPU%d: Unlisted initial frequency changed to: %u KHz\n",
+ __func__, policy->cpu, policy->cur);
+ }
+ }
+
/* related cpus should atleast have policy->cpus */
cpumask_or(policy->related_cpus, policy->related_cpus, policy->cpus);
diff --git a/drivers/cpufreq/freq_table.c b/drivers/cpufreq/freq_table.c
index 3458d27..a8ac042 100644
--- a/drivers/cpufreq/freq_table.c
+++ b/drivers/cpufreq/freq_table.c
@@ -178,7 +178,29 @@ int cpufreq_frequency_table_target(struct cpufreq_policy *policy,
}
EXPORT_SYMBOL_GPL(cpufreq_frequency_table_target);
+int cpufreq_frequency_table_get_index(struct cpufreq_policy *policy,
+ unsigned int freq)
+{
+ struct cpufreq_frequency_table *table;
+ int i;
+
+ table = cpufreq_frequency_get_table(policy->cpu);
+ if (unlikely(!table)) {
+ pr_debug("%s: Unable to find frequency table\n", __func__);
+ return -ENOENT;
+ }
+
+ for (i = 0; table[i].frequency != CPUFREQ_TABLE_END; i++) {
+ if (table[i].frequency == freq)
+ return i;
+ }
+
+ return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(cpufreq_frequency_table_get_index);
+
static DEFINE_PER_CPU(struct cpufreq_frequency_table *, cpufreq_show_table);
+
/**
* show_available_freqs - show available frequencies for the specified CPU
*/
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