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SubjectRe: [PATCH v2 1/1] cpufreq: fix the target freq not in the range of policy->min & max
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->max

Right 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.

> 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--;
> + }

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

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