Re: [PATCH] cpufreq: conservative: Fix incorrect frequency decrease due to stale target

[Stratos Karafotis]

Hi all!

I was struggling to see your point, but I think you are right.

The requested_freq could be equal to policy->min (due to idle periods)
while the dbs_info->requested_freq could be greater than policy->min.
So, in this case it breaks out early without the chance to further 
reduce the frequency, correct?

Stratos Karafotis

On 4/21/26 15:35, Lifeng Zheng wrote:
> In cs_dbs_update(), the requested frequency is decremented by one freq_step
> for each idle period. However, this can cause divergence between
> 'requested_freq' (target for current update) and 'dbs_info->requested_freq'
> (target from previous update).
>
> When the load crosses up_threshold or down_threshold, the decision on
> whether to increase or decrease frequency should be based on the *previous*
> target (dbs_info->requested_freq), not the current one. Otherwise, the
> update step may be skipped entirely if the current target has already hit a
> boundary due to prior adjustments.
>
> Ensure that frequency scaling decisions are made using the correct
> historical target, fixing cases where frequency fails to decrease despite
> sustained idle periods.
>
> Fixes: 00bfe05889e9 ("cpufreq: conservative: Decrease frequency faster for deferred updates")
> Signed-off-by: Lifeng Zheng <zhenglifeng1@xxxxxxxxxx>
> ---
>   drivers/cpufreq/cpufreq_conservative.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/cpufreq/cpufreq_conservative.c b/drivers/cpufreq/cpufreq_conservative.c
> index df01d33993d8..f3c3b54e4bf8 100644
> --- a/drivers/cpufreq/cpufreq_conservative.c
> +++ b/drivers/cpufreq/cpufreq_conservative.c
> @@ -104,7 +104,7 @@ static unsigned int cs_dbs_update(struct cpufreq_policy *policy)
>   		dbs_info->down_skip = 0;
>   
>   		/* if we are already at full speed then break out early */
> -		if (requested_freq == policy->max)
> +		if (dbs_info->requested_freq == policy->max)
>   			goto out;
>   
>   		requested_freq += freq_step;
> @@ -127,7 +127,7 @@ static unsigned int cs_dbs_update(struct cpufreq_policy *policy)
>   		/*
>   		 * if we cannot reduce the frequency anymore, break out early
>   		 */
> -		if (requested_freq == policy->min)
> +		if (dbs_info->requested_freq == policy->min)
>   			goto out;
>   
>   		if (requested_freq > freq_step)