Re: [PATCH] cpufreq: qcom-hw: Fix cpufreq_driver->get() for non-LMH systems

[Konrad Dybcio <konrad.dybcio@linaro.org>]

On 2.02.2023 23:35, Konrad Dybcio wrote:
> 
> 
> On 2.02.2023 23:00, Douglas Anderson wrote:
>> On a sc7180-based Chromebook, when I go to
>> /sys/devices/system/cpu/cpu0/cpufreq I can see:
>>
>>   cpuinfo_cur_freq:2995200
>>   cpuinfo_max_freq:1804800
>>   scaling_available_frequencies:300000 576000 ... 1708800 1804800
>>   scaling_cur_freq:1804800
>>   scaling_max_freq:1804800
>>
>> As you can see the `cpuinfo_cur_freq` is bogus. It turns out that this
>> bogus info started showing up as of commit 205f5e984d30 ("cpufreq:
>> qcom-hw: Fix the frequency returned by cpufreq_driver->get()"). That
>> commit seems to assume that everyone is on the LMH bandwagon, but
>> sc7180 isn't.
>>
>> Let's go back to the old code in the case where LMH isn't used.
>>
>> Fixes: 205f5e984d30 ("cpufreq: qcom-hw: Fix the frequency returned by cpufreq_driver->get()")
>> Signed-off-by: Douglas Anderson <dianders@chromium.org>
>> ---
> Actually I hit the exact same issue when working on CPRh-aware
> cpufreq with manual OSM programming.. LMh gets enabled by the firmware
> on most recent platforms, but it's not the case for some old-timers.
> 
Ignore this email, I can't read.

Konrad
> I figured that adding a bool broken_lmh_freq in driver data would be
> a good middleground between reverting that patch and ignoring the
> issue, because it *does* matter what this function reports on LMh-
> enabled platforms (yes, the subsystems are bluepilled between each
> other and OSM/EPSS does not know the *real* throttled frequency),
> but obviously we don't want to report 2.99Ghz otherwise..
> 
> I think 7280 had an issue where a SoC-specific compatible was not
> introduced when the DT part was first merged, same goes for 6115.
> 6115 does have firmware-enabled LMh, not sure about 7280. In case
> you wanted to go that route, I think it would be suitable to add
> a blacklist of retroactively-broken platforms (match-by-machine-
> compatible; don't scream at me bindings folks, I guess that's the
> least messy solution) in addition to either matching the SoC-specific
> compatible to epss_broken_lmh_driver_data.
> 
> Or we can forget about old DTs and just bind qcom,sc7180-cpufreq-hw
> (and 7280, maybe? please check.) to this new driver data without
> checking the machine compatible.
> 
> 
> 
> Konrad
>>
>>  drivers/cpufreq/qcom-cpufreq-hw.c | 24 +++++++++++++-----------
>>  1 file changed, 13 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/cpufreq/qcom-cpufreq-hw.c b/drivers/cpufreq/qcom-cpufreq-hw.c
>> index 9505a812d6a1..957cf6bb8c05 100644
>> --- a/drivers/cpufreq/qcom-cpufreq-hw.c
>> +++ b/drivers/cpufreq/qcom-cpufreq-hw.c
>> @@ -143,40 +143,42 @@ static unsigned long qcom_lmh_get_throttle_freq(struct qcom_cpufreq_data *data)
>>  	return lval * xo_rate;
>>  }
>>  
>> -/* Get the current frequency of the CPU (after throttling) */
>> -static unsigned int qcom_cpufreq_hw_get(unsigned int cpu)
>> +/* Get the frequency requested by the cpufreq core for the CPU */
>> +static unsigned int qcom_cpufreq_get_freq(unsigned int cpu)
>>  {
>>  	struct qcom_cpufreq_data *data;
>> +	const struct qcom_cpufreq_soc_data *soc_data;
>>  	struct cpufreq_policy *policy;
>> +	unsigned int index;
>>  
>>  	policy = cpufreq_cpu_get_raw(cpu);
>>  	if (!policy)
>>  		return 0;
>>  
>>  	data = policy->driver_data;
>> +	soc_data = qcom_cpufreq.soc_data;
>>  
>> -	return qcom_lmh_get_throttle_freq(data) / HZ_PER_KHZ;
>> +	index = readl_relaxed(data->base + soc_data->reg_perf_state);
>> +	index = min(index, LUT_MAX_ENTRIES - 1);
>> +
>> +	return policy->freq_table[index].frequency;
>>  }
>>  
>> -/* Get the frequency requested by the cpufreq core for the CPU */
>> -static unsigned int qcom_cpufreq_get_freq(unsigned int cpu)
>> +static unsigned int qcom_cpufreq_hw_get(unsigned int cpu)
>>  {
>>  	struct qcom_cpufreq_data *data;
>> -	const struct qcom_cpufreq_soc_data *soc_data;
>>  	struct cpufreq_policy *policy;
>> -	unsigned int index;
>>  
>>  	policy = cpufreq_cpu_get_raw(cpu);
>>  	if (!policy)
>>  		return 0;
>>  
>>  	data = policy->driver_data;
>> -	soc_data = qcom_cpufreq.soc_data;
>>  
>> -	index = readl_relaxed(data->base + soc_data->reg_perf_state);
>> -	index = min(index, LUT_MAX_ENTRIES - 1);
>> +	if (data->throttle_irq >= 0)
>> +		return qcom_lmh_get_throttle_freq(data) / HZ_PER_KHZ;
>>  
>> -	return policy->freq_table[index].frequency;
>> +	return qcom_cpufreq_get_freq(cpu);
>>  }
>>  
>>  static unsigned int qcom_cpufreq_hw_fast_switch(struct cpufreq_policy *policy,