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>

1 files changed, 22 insertions, 0 deletions

diff --git a/drivers/cpufreq/freq_table.c b/drivers/cpufreq/freq_table.c
index 3458d27f63b..a8ac0427fbf 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
  */