This is a note to let you know that I've just added the patch titled
cpufreq: Make policy min/max hard requirements
to the 5.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
cpufreq-make-policy-min-max-hard-requirements.patch
and it can be found in the queue-5.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 8f00330a1e8710fce315f5560a8dd129bf0abc64
Author: Vincent Donnefort <vincent.donnefort@xxxxxxx>
Date: Wed Sep 8 15:05:26 2021 +0100
cpufreq: Make policy min/max hard requirements
[ Upstream commit 15171769069408789a72f9aa9a52cc931b839b56 ]
When applying the policy min/max limits, the requested frequency is
simply clamped to not be out of range. It means, however, if one of the
boundaries isn't an available frequency, the frequency resolution can
return a value out of those limits, depending on the relation used.
e.g. freq{0,1,2} being available frequencies.
freq0 policy->min freq1 policy->max freq2
| | | | |
17kHz 18kHz 19kHz 20kHz 21kHz
__resolve_freq(21kHz, CPUFREQ_RELATION_L) -> 21kHz (out of bounds)
__resolve_freq(17kHz, CPUFREQ_RELATION_H) -> 17kHz (out of bounds)
If, during the policy init, we resolve the requested min/max to existing
frequencies, we ensure that any CPUFREQ_RELATION_* would resolve to a
frequency which is inside the policy min/max range.
Making the policy limits rigid helps to introduce the inefficient
frequencies support. Resolving an inefficient frequency to an efficient
one should not transgress policy->max (which can be set for thermal
reason) and having a value we can trust simplify this comparison.
Signed-off-by: Vincent Donnefort <vincent.donnefort@xxxxxxx>
Acked-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 45f3416988f1a..2c003d193c69b 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -2514,8 +2514,15 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
if (ret)
return ret;
+ /*
+ * Resolve policy min/max to available frequencies. It ensures
+ * no frequency resolution will neither overshoot the requested maximum
+ * nor undershoot the requested minimum.
+ */
policy->min = new_data.min;
policy->max = new_data.max;
+ policy->min = __resolve_freq(policy, policy->min, CPUFREQ_RELATION_L);
+ policy->max = __resolve_freq(policy, policy->max, CPUFREQ_RELATION_H);
trace_cpu_frequency_limits(policy);
policy->cached_target_freq = UINT_MAX;
