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Date:   Thu, 21 May 2020 14:25:26 +0800
From:   Xiongfeng Wang <wangxiongfeng2@...wei.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
CC:     <rjw@...ysocki.net>, <Souvik.Chakravarty@....com>,
        <Thanu.Rangarajan@....com>, <Sudeep.Holla@....com>,
        <guohanjun@...wei.com>, <john.garry@...wei.com>,
        <jonathan.cameron@...wei.com>, <linux-pm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v3 2/2] CPPC: add support for SW BOOST

Hi Viresh,

On 2020/5/20 13:00, Viresh Kumar wrote:
> On 19-05-20, 19:41, Xiongfeng Wang wrote:
>> To add SW BOOST support for CPPC, we need to get the max frequency of
>> boost mode and non-boost mode. ACPI spec 6.2 section 8.4.7.1 describe
>> the following two CPC registers.
>>
>> "Highest performance is the absolute maximum performance an individual
>> processor may reach, assuming ideal conditions. This performance level
>> may not be sustainable for long durations, and may only be achievable if
>> other platform components are in a specific state; for example, it may
>> require other processors be in an idle state.
>>
>> Nominal Performance is the maximum sustained performance level of the
>> processor, assuming ideal operating conditions. In absence of an
>> external constraint (power, thermal, etc.) this is the performance level
>> the platform is expected to be able to maintain continuously. All
>> processors are expected to be able to sustain their nominal performance
>> state simultaneously."
>>
>> To add SW BOOST support for CPPC, we can use Highest Performance as the
>> max performance in boost mode and Nominal Performance as the max
>> performance in non-boost mode. If the Highest Performance is greater
>> than the Nominal Performance, we assume SW BOOST is supported.
>>
>> The current CPPC driver does not support SW BOOST and use 'Highest
>> Performance' as the max performance the CPU can achieve. 'Nominal
>> Performance' is used to convert 'performance' to 'frequency'. That
>> means, if firmware enable boost and provide a value for Highest
>> Performance which is greater than Nominal Performance, boost feature is
>> enabled by default.
>>
>> Because SW BOOST is disabled by default, so, after this patch, boost
>> feature is disabled by default even if boost is enabled by firmware.
>>
>> Signed-off-by: Xiongfeng Wang <wangxiongfeng2@...wei.com>
>> ---
>>  drivers/cpufreq/cppc_cpufreq.c | 39 +++++++++++++++++++++++++++++++++++++--
>>  1 file changed, 37 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
>> index bda0b24..792ed9e 100644
>> --- a/drivers/cpufreq/cppc_cpufreq.c
>> +++ b/drivers/cpufreq/cppc_cpufreq.c
>> @@ -37,6 +37,7 @@
>>   * requested etc.
>>   */
>>  static struct cppc_cpudata **all_cpu_data;
>> +static bool boost_supported;
>>  
>>  struct cppc_workaround_oem_info {
>>  	char oem_id[ACPI_OEM_ID_SIZE + 1];
>> @@ -310,7 +311,7 @@ static int cppc_cpufreq_cpu_init(struct cpufreq_policy *policy)
>>  	 * Section 8.4.7.1.1.5 of ACPI 6.1 spec)
>>  	 */
>>  	policy->min = cppc_cpufreq_perf_to_khz(cpu, cpu->perf_caps.lowest_nonlinear_perf);
>> -	policy->max = cppc_cpufreq_perf_to_khz(cpu, cpu->perf_caps.highest_perf);
>> +	policy->max = cppc_cpufreq_perf_to_khz(cpu, cpu->perf_caps.nominal_perf);
>>  
>>  	/*
>>  	 * Set cpuinfo.min_freq to Lowest to make the full range of performance
>> @@ -318,7 +319,7 @@ static int cppc_cpufreq_cpu_init(struct cpufreq_policy *policy)
>>  	 * nonlinear perf
>>  	 */
>>  	policy->cpuinfo.min_freq = cppc_cpufreq_perf_to_khz(cpu, cpu->perf_caps.lowest_perf);
>> -	policy->cpuinfo.max_freq = cppc_cpufreq_perf_to_khz(cpu, cpu->perf_caps.highest_perf);
>> +	policy->cpuinfo.max_freq = cppc_cpufreq_perf_to_khz(cpu, cpu->perf_caps.nominal_perf);
>>  
>>  	policy->transition_delay_us = cppc_cpufreq_get_transition_delay_us(cpu_num);
>>  	policy->shared_type = cpu->shared_type;
>> @@ -343,6 +344,13 @@ static int cppc_cpufreq_cpu_init(struct cpufreq_policy *policy)
>>  
>>  	cpu->cur_policy = policy;
>>  
>> +	/*
>> +	 * If 'highest_perf' is greater than 'nominal_perf', we assume CPU Boost
>> +	 * is supported.
>> +	 */
>> +	if (cpu->perf_caps.highest_perf > cpu->perf_caps.nominal_perf)
>> +		boost_supported = true;
>> +
>>  	/* Set policy->cur to max now. The governors will adjust later. */
>>  	policy->cur = cppc_cpufreq_perf_to_khz(cpu,
>>  					cpu->perf_caps.highest_perf);
>> @@ -410,6 +418,32 @@ static unsigned int cppc_cpufreq_get_rate(unsigned int cpunum)
>>  	return cppc_get_rate_from_fbctrs(cpu, fb_ctrs_t0, fb_ctrs_t1);
>>  }
>>  
>> +static int cppc_cpufreq_set_boost(struct cpufreq_policy *policy, int state)
>> +{
>> +	struct cppc_cpudata *cpudata;
>> +	int ret = 0;
> 
> No need to initialize this.

I will change it in the next version.

Thanks for your advice. I will add your 'Suggested-by' for these two patches.


Thanks,
Xiongfeng

> 
>> +
>> +	if (!boost_supported) {
>> +		pr_err("BOOST not supported by CPU or firmware\n");
>> +		return -EINVAL;
>> +	}
>> +
>> +	cpudata = all_cpu_data[policy->cpu];
>> +	if (state)
>> +		policy->max = cppc_cpufreq_perf_to_khz(cpudata,
>> +					cpudata->perf_caps.highest_perf);
>> +	else
>> +		policy->max = cppc_cpufreq_perf_to_khz(cpudata,
>> +					cpudata->perf_caps.nominal_perf);
>> +	policy->cpuinfo.max_freq = policy->max;
>> +
>> +	ret = freq_qos_update_request(policy->max_freq_req, policy->max);
>> +	if (ret < 0)
>> +		return ret;
>> +
>> +	return 0;
>> +}
>> +
>>  static struct cpufreq_driver cppc_cpufreq_driver = {
>>  	.flags = CPUFREQ_CONST_LOOPS,
>>  	.verify = cppc_verify_policy,
>> @@ -417,6 +451,7 @@ static unsigned int cppc_cpufreq_get_rate(unsigned int cpunum)
>>  	.get = cppc_cpufreq_get_rate,
>>  	.init = cppc_cpufreq_cpu_init,
>>  	.stop_cpu = cppc_cpufreq_stop_cpu,
>> +	.set_boost = cppc_cpufreq_set_boost,
>>  	.name = "cppc_cpufreq",
>>  };
>>  
>> -- 
>> 1.7.12.4
> 

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