Re: [PATCH v2 1/1] cpufreq: fix the target freq not in the range of policy->min & max
From: Viresh Kumar <viresh.kumar@linaro.org>
Date: 2021-06-29 06:18:06
Also in:
linux-arm-kernel, linux-mediatek, lkml
On 27-06-21, 00:23, TungChen Shih wrote:
The function cpufreq_driver_resolve_freq() should return the lowest
Don't add extra spaces at the beginning of paragraphs here.
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->maxRight so the problem does exist, and not only with cpufreq_driver_resolve_freq(), but __cpufreq_driver_target() as well. I have a sent a patchset to update both of these to start sharing some code and we need to fix this for both now.
quoted hunk ↗ jump to hunk
Signed-off-by: TungChen Shih <redacted> --- 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--; + }
This doesn't look clean to be honest. Rafael, does it make sense to update cpufreq_frequency_table_target() (and its internal routines) to take policy bounds in consideration, or something else ? -- viresh