[PATCH] cpufreq: Use a smaller freq for the policy->max when verify

[PATCH] cpufreq: Use a smaller freq for the policy->max when verify

[Xuewen Yan]

When driver use the cpufreq_frequency_table_verify() as the
cpufreq_driver->verify's callback. It may cause the policy->max
bigger than the freq_qos's max freq.

Just as follow:

unisoc:/sys/devices/system/cpu/cpufreq/policy0 # cat scaling_available_frequencies
614400 768000 988000 1228800 1469000 1586000 1690000 1833000 2002000 2093000

unisoc:/sys/devices/system/cpu/cpufreq/policy0 # echo 1900000 > scaling_max_freq
unisoc:/sys/devices/system/cpu/cpufreq/policy0 # echo 1900000 > scaling_min_freq
unisoc:/sys/devices/system/cpu/cpufreq/policy0 # cat scaling_max_freq
2002000
unisoc:/sys/devices/system/cpu/cpufreq/policy0 # cat scaling_min_freq
2002000

When user set the qos_min and qos_max as the same value, and the value
is not in the freq-table, the above scenario will occur.

This is because in cpufreq_frequency_table_verify() func, when it can not
find the freq in table, it will change the policy->max to be a bigger freq,
as above, because there is no 1.9G in the freq-table, the policy->max would
be set to 2.002G. As a result, the cpufreq_policy->max is bigger than the
user's qos_max. This is unreasonable.

So use a smaller freq when can not find the freq in fre-table, to prevent
the policy->max exceed the qos's max freq.

Signed-off-by: Xuewen Yan <xuewen.yan@unisoc.com>
---
 drivers/cpufreq/freq_table.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/cpufreq/freq_table.c b/drivers/cpufreq/freq_table.c
index c4d4643b6ca6..1d98b8cf1688 100644
--- a/drivers/cpufreq/freq_table.c
+++ b/drivers/cpufreq/freq_table.c
@@ -70,7 +70,7 @@ int cpufreq_frequency_table_verify(struct cpufreq_policy_data *policy,
 				   struct cpufreq_frequency_table *table)
 {
 	struct cpufreq_frequency_table *pos;
-	unsigned int freq, next_larger = ~0;
+	unsigned int freq, prev_smaller = 0;
 	bool found = false;
 
 	pr_debug("request for verification of policy (%u - %u kHz) for cpu %u\n",
@@ -86,12 +86,12 @@ int cpufreq_frequency_table_verify(struct cpufreq_policy_data *policy,
 			break;
 		}
 
-		if ((next_larger > freq) && (freq > policy->max))
-			next_larger = freq;
+		if ((prev_smaller < freq) && (freq <= policy->max))
+			prev_smaller = freq;
 	}
 
 	if (!found) {
-		policy->max = next_larger;
+		policy->max = prev_smaller;
 		cpufreq_verify_within_cpu_limits(policy);
 	}
 
-- 
2.25.1

Re: [PATCH] cpufreq: Use a smaller freq for the policy->max when verify

[Viresh Kumar]

On 19-03-24, 16:01, Xuewen Yan wrote:
> When driver use the cpufreq_frequency_table_verify() as the
> cpufreq_driver->verify's callback. It may cause the policy->max
> bigger than the freq_qos's max freq.
> 
> Just as follow:
> 
> unisoc:/sys/devices/system/cpu/cpufreq/policy0 # cat scaling_available_frequencies
> 614400 768000 988000 1228800 1469000 1586000 1690000 1833000 2002000 2093000
> 
> unisoc:/sys/devices/system/cpu/cpufreq/policy0 # echo 1900000 > scaling_max_freq
> unisoc:/sys/devices/system/cpu/cpufreq/policy0 # echo 1900000 > scaling_min_freq
> unisoc:/sys/devices/system/cpu/cpufreq/policy0 # cat scaling_max_freq
> 2002000
> unisoc:/sys/devices/system/cpu/cpufreq/policy0 # cat scaling_min_freq
> 2002000
> 
> When user set the qos_min and qos_max as the same value, and the value
> is not in the freq-table, the above scenario will occur.
> 
> This is because in cpufreq_frequency_table_verify() func, when it can not
> find the freq in table, it will change the policy->max to be a bigger freq,
> as above, because there is no 1.9G in the freq-table, the policy->max would
> be set to 2.002G. As a result, the cpufreq_policy->max is bigger than the
> user's qos_max. This is unreasonable.
> 
> So use a smaller freq when can not find the freq in fre-table, to prevent

                                                      freq-table

> the policy->max exceed the qos's max freq.
> 
> Signed-off-by: Xuewen Yan <xuewen.yan@unisoc.com>
> ---
>  drivers/cpufreq/freq_table.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)

Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

-- 
viresh

Re: [PATCH] cpufreq: Use a smaller freq for the policy->max when verify

[Rafael J. Wysocki]

On Wed, Mar 20, 2024 at 4:21 AM Viresh Kumar <viresh.kumar@linaro.org> wrote:
>
> On 19-03-24, 16:01, Xuewen Yan wrote:
> > When driver use the cpufreq_frequency_table_verify() as the
> > cpufreq_driver->verify's callback. It may cause the policy->max
> > bigger than the freq_qos's max freq.
> >
> > Just as follow:
> >
> > unisoc:/sys/devices/system/cpu/cpufreq/policy0 # cat scaling_available_frequencies
> > 614400 768000 988000 1228800 1469000 1586000 1690000 1833000 2002000 2093000
> >
> > unisoc:/sys/devices/system/cpu/cpufreq/policy0 # echo 1900000 > scaling_max_freq
> > unisoc:/sys/devices/system/cpu/cpufreq/policy0 # echo 1900000 > scaling_min_freq
> > unisoc:/sys/devices/system/cpu/cpufreq/policy0 # cat scaling_max_freq
> > 2002000
> > unisoc:/sys/devices/system/cpu/cpufreq/policy0 # cat scaling_min_freq
> > 2002000
> >
> > When user set the qos_min and qos_max as the same value, and the value
> > is not in the freq-table, the above scenario will occur.
> >
> > This is because in cpufreq_frequency_table_verify() func, when it can not
> > find the freq in table, it will change the policy->max to be a bigger freq,
> > as above, because there is no 1.9G in the freq-table, the policy->max would
> > be set to 2.002G. As a result, the cpufreq_policy->max is bigger than the
> > user's qos_max. This is unreasonable.
> >
> > So use a smaller freq when can not find the freq in fre-table, to prevent
>
>                                                       freq-table
>
> > the policy->max exceed the qos's max freq.
> >
> > Signed-off-by: Xuewen Yan <xuewen.yan@unisoc.com>
> > ---
> >  drivers/cpufreq/freq_table.c | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
>
> Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

Applied as 6.10 material, thanks!

Re: [PATCH] cpufreq: Use a smaller freq for the policy->max when verify

[Dhruva Gole]

Hi,

On Mar 19, 2024 at 16:01:53 +0800, Xuewen Yan wrote:
> When driver use the cpufreq_frequency_table_verify() as the
> cpufreq_driver->verify's callback. It may cause the policy->max
> bigger than the freq_qos's max freq.
> 
> Just as follow:
> 
> unisoc:/sys/devices/system/cpu/cpufreq/policy0 # cat scaling_available_frequencies
> 614400 768000 988000 1228800 1469000 1586000 1690000 1833000 2002000 2093000
> 
> unisoc:/sys/devices/system/cpu/cpufreq/policy0 # echo 1900000 > scaling_max_freq
> unisoc:/sys/devices/system/cpu/cpufreq/policy0 # echo 1900000 > scaling_min_freq
> unisoc:/sys/devices/system/cpu/cpufreq/policy0 # cat scaling_max_freq
> 2002000
> unisoc:/sys/devices/system/cpu/cpufreq/policy0 # cat scaling_min_freq
> 2002000
> 
> When user set the qos_min and qos_max as the same value, and the value
> is not in the freq-table, the above scenario will occur.
> 
> This is because in cpufreq_frequency_table_verify() func, when it can not
> find the freq in table, it will change the policy->max to be a bigger freq,
> as above, because there is no 1.9G in the freq-table, the policy->max would
> be set to 2.002G. As a result, the cpufreq_policy->max is bigger than the
> user's qos_max. This is unreasonable.

That's a good catch! Never thought of this.

> 
> So use a smaller freq when can not find the freq in fre-table, to prevent
> the policy->max exceed the qos's max freq.
> 
> Signed-off-by: Xuewen Yan <xuewen.yan@unisoc.com>
> ---
>  drivers/cpufreq/freq_table.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/cpufreq/freq_table.c b/drivers/cpufreq/freq_table.c
> index c4d4643b6ca6..1d98b8cf1688 100644
> --- a/drivers/cpufreq/freq_table.c
> +++ b/drivers/cpufreq/freq_table.c
> @@ -70,7 +70,7 @@ int cpufreq_frequency_table_verify(struct cpufreq_policy_data *policy,
>  				   struct cpufreq_frequency_table *table)
>  {
>  	struct cpufreq_frequency_table *pos;
> -	unsigned int freq, next_larger = ~0;
> +	unsigned int freq, prev_smaller = 0;
>  	bool found = false;
>  
>  	pr_debug("request for verification of policy (%u - %u kHz) for cpu %u\n",
> @@ -86,12 +86,12 @@ int cpufreq_frequency_table_verify(struct cpufreq_policy_data *policy,
>  			break;
>  		}
>  
> -		if ((next_larger > freq) && (freq > policy->max))
> -			next_larger = freq;
> +		if ((prev_smaller < freq) && (freq <= policy->max))
> +			prev_smaller = freq;
>  	}
>  
>  	if (!found) {
> -		policy->max = next_larger;
> +		policy->max = prev_smaller;
>  		cpufreq_verify_within_cpu_limits(policy);

LGTM!
Reviewed-by: Dhruva Gole <d-gole@ti.com>

-- 
Best regards,
Dhruva