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Subject[PATCH v2 1/1] cpufreq: fix the target freq not in the range of policy->min & max
Date
    The function cpufreq_driver_resolve_freq() should return the lowest
supported freq greater than or equal to the given target_freq, subject
to policy (min/max) and driver limitations. However, the index returned
by cpufreq_frequency_table_target() won't subject to policy min/max in
some cases.

In cpufreq_frequency_table_target(), this function will try to find
an index for @target_freq in freq_table, and the frequency of selected
index should be in the range [policy->min, policy->max], which means:

policy->min <= policy->freq_table[idx].frequency <= policy->max

Though "clamp_val(target_freq, policy->min, policy->max);" would
have been called to check this condition, when policy->max or min is
not exactly one of the frequency in the frequency table,
policy->freq_table[idx].frequency may still go out of the range

For example, if our sorted freq_table is [3000, 2000, 1000], and
suppose we have:

@target_freq = 2500
@policy->min = 2000
@policy->max = 2200
@relation = CPUFREQ_RELATION_L

1. After clamp_val(target_freq, policy->min, policy->max); @target_freq
becomes 2200
2. Since we use CPUFREQ_REALTION_L, final selected freq will be 3000 which
beyonds policy->max

Signed-off-by: TungChen Shih <tung-chen.shih@mediatek.com>
---
drivers/cpufreq/cpufreq.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 802abc925b2a..8e3a17781618 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -544,8 +544,23 @@ unsigned int cpufreq_driver_resolve_freq(struct cpufreq_policy *policy,
if (cpufreq_driver->target_index) {
unsigned int idx;

+ /* to find the frequency >= target_freq */
idx = cpufreq_frequency_table_target(policy, target_freq,
CPUFREQ_RELATION_L);
+
+ /* frequency should subject to policy (min/max) */
+ if (policy->freq_table[idx].frequency > policy->max) {
+ if (policy->freq_table_sorted == CPUFREQ_TABLE_SORTED_ASCENDING)
+ idx--;
+ else
+ idx++;
+ } else if (policy->freq_table[idx].frequency < policy->min) {
+ if (policy->freq_table_sorted == CPUFREQ_TABLE_SORTED_ASCENDING)
+ idx++;
+ else
+ idx--;
+ }
+
policy->cached_resolved_idx = idx;
return policy->freq_table[idx].frequency;
}
--
2.18.0
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