linux-kernel - Re: [PATCH] cpufreq: freq_table: Initialize cpuinfo.max

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Date:   Tue, 16 Nov 2021 10:27:33 -0500
From:   Thara Gopinath <thara.gopinath@...aro.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>,
        Steev Klimaszewski <steev@...i.org>
Cc:     rafael@...nel.org, bjorn.andersson@...aro.org,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH] cpufreq: freq_table: Initialize cpuinfo.max_freq to
 correct max frequency.



On 11/15/21 10:59 PM, Viresh Kumar wrote:
> On 15-11-21, 19:23, Steev Klimaszewski wrote:
>> Hi Thara,
>>
>> On 11/15/21 1:50 PM, Thara Gopinath wrote:
>>> cpuinfo.max_freq reflects the maximum supported frequency of cpus in a
>>> cpufreq policy. When cpus support boost frequency and if boost is disabled
>>> during boot up (which is the default), cpuinfo.max_freq does not reflect
>>> boost frequency as the maximum supported frequency till boost is explicitly
>>> enabled via sysfs interface later. This also means that policy reports two
>>> different cpuinfo.max_freq before and after turning on boost.  Fix this by
>>> separating out setting of policy->max and cpuinfo.max_freq in
>>> cpufreq_frequency_table_cpuinfo.
>>>
>>> e.g. of the problem. Qualcomm sdm845 supports boost frequency for gold
>>> cluster (cpus 4-7). After boot up (boost disabled),
>>>
>>> 1.  cat /sys/devices/system/cpu/cpufreq/policy4/cpuinfo_max_freq 2649600
>>> <- This is wrong because boost frequency is
>>>
>>> 2.  echo 1 > /sys/devices/system/cpu/cpufreq/boost  <- Enable boost cat
>>> /sys/devices/system/cpu/cpufreq/policy4/cpuinfo_max_freq 2803200	<-
>>> max freq reflects boost freq.
>>>
>>> 3.  echo 0 > /sys/devices/system/cpu/cpufreq/boost <- Disable boost cat
>>> /sys/devices/system/cpu/cpufreq/policy4/cpuinfo_max_freq 2803200	<-
>>> Discrepancy with step 1 as in both cases boost is disabled.
>>>
>>> Note that the other way to fix this is to set cpuinfo.max_freq in Soc
>>> cpufreq driver during initialization. Fixing it in
>>> cpufreq_frequency_table_cpuinfo seems more generic solution
>>>
>>> Signed-off-by: Thara Gopinath <thara.gopinath@...aro.org>
>>> ---
>>>    drivers/cpufreq/freq_table.c | 8 ++++++--
>>>    1 file changed, 6 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/cpufreq/freq_table.c b/drivers/cpufreq/freq_table.c
>>> index 67e56cf638ef..6784f94124df 100644
>>> --- a/drivers/cpufreq/freq_table.c
>>> +++ b/drivers/cpufreq/freq_table.c
>>> @@ -35,11 +35,15 @@ int cpufreq_frequency_table_cpuinfo(struct cpufreq_policy *policy,
>>>    	struct cpufreq_frequency_table *pos;
>>>    	unsigned int min_freq = ~0;
>>>    	unsigned int max_freq = 0;
>>> +	unsigned int cpuinfo_max_freq = 0;
>>>    	unsigned int freq;
>>>    	cpufreq_for_each_valid_entry(pos, table) {
>>>    		freq = pos->frequency;
>>> +		if (freq > cpuinfo_max_freq)
>>> +			cpuinfo_max_freq = freq;
>>> +
>>>    		if (!cpufreq_boost_enabled()
>>>    		    && (pos->flags & CPUFREQ_BOOST_FREQ))
>>>    			continue;
>>> @@ -57,8 +61,8 @@ int cpufreq_frequency_table_cpuinfo(struct cpufreq_policy *policy,
>>>    	 * If the driver has set its own cpuinfo.max_freq above max_freq, leave
>>>    	 * it as is.
>>>    	 */
>>> -	if (policy->cpuinfo.max_freq < max_freq)
>>> -		policy->max = policy->cpuinfo.max_freq = max_freq;
>>> +	if (policy->cpuinfo.max_freq < cpuinfo_max_freq)
>>> +		policy->cpuinfo.max_freq = cpuinfo_max_freq;
> 
> You need to keep the check of policy->max here and update policy->max,
> else you will never run at boost freq. I think this is what Steev
> reported as well ?

Hi Viresh,
	policy->max is unconditionally set to max_freq in the line before "if 
(policy->cpuinfo.max_freq < max_freq)". So this is not the issue Steev 
is reporting.
	policy->max = max_freq


> 
> So basically something like this:
> 
> 	if (policy->max < max_freq)
> 		policy->max = max_freq;
> 
> 	if (policy->cpuinfo.max_freq < cpuinfo_max_freq)
> 		policy->cpuinfo.max_freq = cpuinfo_max_freq;
> 

-- 
Warm Regards
Thara (She/Her/Hers)