Date:   Fri, 19 Jul 2019 10:09:57 +0900
From:   Chanwoo Choi <cw00.choi@...sung.com>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        linux-pm@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 18/24] PM / devfreq: tegra30: Optimize CPUFreq
 notifier

On 19. 7. 19. 오전 9:42, Dmitry Osipenko wrote:
> В Thu, 18 Jul 2019 18:48:42 +0900
> Chanwoo Choi <cw00.choi@...sung.com> пишет:
> 
>> On 19. 7. 8. 오전 7:32, Dmitry Osipenko wrote:
>>> When CPU's memory activity is low or memory activity is high such
>>> that CPU's frequency contribution to the boosting is not taken into
>>> account, then there is no need to schedule devfreq's update. This
>>> eliminates unnecessary CPU activity during of idling caused by the
>>> scheduled work.
>>>
>>> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
>>> ---
>>>  drivers/devfreq/tegra30-devfreq.c | 73
>>> +++++++++++++++++++++++++++---- 1 file changed, 64 insertions(+), 9
>>> deletions(-)  
>>
>> Patch4 add the 'cpufreq notifier' and this patch optimize the cpufreq
>> notifier. I think t hat you can combine two patches.
> 
> I'd prefer to keep them separate for a sake of git bisection.

Sorry, patch7 instead of patch4.

Patch7 made the 'tegra_actmon_cpu_notify_cb()' function
and this patch makes 'tegra_actmon_cpufreq_contribution' function
which is only called in the 'tegra_actmon_cpu_notify_cb()' function.

It is enough to make them as the only one patch related to
the cpu notifier. As I replied on patch17, you can merge
the patch if the patches has some relationship in this patchset.

> 
>>>
>>> diff --git a/drivers/devfreq/tegra30-devfreq.c
>>> b/drivers/devfreq/tegra30-devfreq.c index
>>> 43c9c5fbfe91..8d6bf6e9f1ae 100644 ---
>>> a/drivers/devfreq/tegra30-devfreq.c +++
>>> b/drivers/devfreq/tegra30-devfreq.c @@ -216,10 +216,10 @@ static
>>> inline unsigned long do_percent(unsigned long val, unsigned int
>>> pct) return val * pct / 100; }
>>>  
>>> -static unsigned long actmon_cpu_to_emc_rate(struct tegra_devfreq
>>> *tegra) +static unsigned long actmon_cpu_to_emc_rate(struct
>>> tegra_devfreq *tegra,
>>> +					    unsigned int cpu_freq)
>>>  {
>>>  	const struct tegra_actmon_emc_ratio *ratio =
>>> actmon_emc_ratios;
>>> -	unsigned int cpu_freq = cpufreq_get(0);
>>>  	unsigned int i;
>>>  
>>>  	for (i = 0; i < ARRAY_SIZE(actmon_emc_ratios); i++,
>>> ratio++) { @@ -239,15 +239,15 @@
>>> tegra_actmon_account_cpu_freq(struct tegra_devfreq *tegra, struct
>>> tegra_devfreq_device *dev, unsigned long target_freq)
>>>  {
>>> -	unsigned long static_cpu_emc_freq;
>>> +	unsigned long cpu_emc_freq = 0;
>>>  
>>> -	if (dev->config->avg_dependency_threshold &&
>>> -	    dev->config->avg_dependency_threshold < dev->avg_freq)
>>> {
>>> -		static_cpu_emc_freq =
>>> actmon_cpu_to_emc_rate(tegra);
>>> -		target_freq = max(target_freq,
>>> static_cpu_emc_freq);
>>> -	}
>>> +	if (!dev->config->avg_dependency_threshold)
>>> +		return target_freq;
>>>  
>>> -	return target_freq;
>>> +	if (dev->avg_freq > dev->config->avg_dependency_threshold)
>>> +		cpu_emc_freq = actmon_cpu_to_emc_rate(tegra,
>>> cpufreq_get(0)); +
>>> +	return max(target_freq, cpu_emc_freq);
>>>  }
>>>  
>>>  static unsigned long tegra_actmon_lower_freq(struct tegra_devfreq
>>> *tegra, @@ -531,16 +531,71 @@ static void
>>> tegra_actmon_delayed_update(struct work_struct *work)
>>> mutex_unlock(&tegra->devfreq->lock); }
>>>  
>>> +static unsigned long
>>> +tegra_actmon_cpufreq_contribution(struct tegra_devfreq *tegra,
>>> +				  unsigned int cpu_freq)
>>> +{
>>> +	unsigned long freq, static_cpu_emc_freq;
>>> +
>>> +	/* check whether CPU's freq is taken into account at all */
>>> +	if (tegra->devices[MCCPU].avg_freq <=
>>> +	    tegra->devices[MCCPU].config->avg_dependency_threshold)
>>> +		return 0;
>>> +
>>> +	static_cpu_emc_freq = actmon_cpu_to_emc_rate(tegra,
>>> cpu_freq); +
>>> +	/* compare static CPU-EMC freq with MCALL */
>>> +	freq = tegra->devices[MCALL].avg_freq +
>>> +	       tegra->devices[MCALL].boost_freq;
>>> +
>>> +	freq = tegra_actmon_upper_freq(tegra, freq);
>>> +
>>> +	if (freq == tegra->max_freq || freq >= static_cpu_emc_freq)
>>> +		return 0;
>>> +
>>> +	/* compare static CPU-EMC freq with MCCPU */
>>> +	freq = tegra->devices[MCCPU].avg_freq +
>>> +	       tegra->devices[MCCPU].boost_freq;
>>> +
>>> +	freq = tegra_actmon_upper_freq(tegra, freq);
>>> +
>>> +	if (freq == tegra->max_freq || freq >= static_cpu_emc_freq)
>>> +		return 0;
>>> +
>>> +	return static_cpu_emc_freq;
>>> +}
>>> +
>>>  static int tegra_actmon_cpu_notify_cb(struct notifier_block *nb,
>>>  				      unsigned long action, void
>>> *ptr) {
>>> +	struct cpufreq_freqs *freqs = ptr;
>>>  	struct tegra_devfreq *tegra;
>>> +	unsigned long old, new;
>>>  
>>>  	if (action != CPUFREQ_POSTCHANGE)
>>>  		return NOTIFY_OK;
>>>  
>>>  	tegra = container_of(nb, struct tegra_devfreq,
>>> cpu_rate_change_nb); 
>>> +	/*
>>> +	 * Quickly check whether CPU frequency should be taken
>>> into account
>>> +	 * at all, without blocking CPUFreq's core.
>>> +	 */
>>> +	if (mutex_trylock(&tegra->devfreq->lock)) {
>>> +		old = tegra_actmon_cpufreq_contribution(tegra,
>>> freqs->old);
>>> +		new = tegra_actmon_cpufreq_contribution(tegra,
>>> freqs->new);
>>> +		mutex_unlock(&tegra->devfreq->lock);
>>> +
>>> +		/*
>>> +		 * If CPU's frequency shouldn't be taken into
>>> account at
>>> +		 * the moment, then there is no need to update the
>>> devfreq's
>>> +		 * state because ISR will re-check CPU's frequency
>>> on the
>>> +		 * next interrupt.
>>> +		 */
>>> +		if (old == new)
>>> +			return NOTIFY_OK;
>>> +	}
>>> +
>>>  	/*
>>>  	 * CPUFreq driver should support
>>> CPUFREQ_ASYNC_NOTIFICATION in order
>>>  	 * to allow asynchronous notifications. This means we
>>> can't block 
>>
>>
> 
> 
> 


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics

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