linux-kernel - Re: [PATCH v4 02/24] PM / devfreq: tegra30: Keep interrupt disabled while governor is stopped

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Date:   Wed, 17 Jul 2019 15:37:28 +0900
From:   Chanwoo Choi <cw00.choi@...sung.com>
To:     Dmitry Osipenko <digetx@...il.com>,
        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>
Cc:     linux-pm@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 02/24] PM / devfreq: tegra30: Keep interrupt disabled
 while governor is stopped

On 19. 7. 16. 오후 10:03, Dmitry Osipenko wrote:
> 16.07.2019 14:47, Chanwoo Choi пишет:
>> On 19. 7. 8. 오전 7:32, Dmitry Osipenko wrote:
>>> There is no real need to keep interrupt always-enabled, will be nicer
>>> to keep it disabled while governor is inactive.
>>>
>>> Suggested-by: Thierry Reding <thierry.reding@...il.com>
>>> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
>>> ---
>>>  drivers/devfreq/tegra30-devfreq.c | 43 ++++++++++++++++---------------
>>>  1 file changed, 22 insertions(+), 21 deletions(-)
>>>
>>> diff --git a/drivers/devfreq/tegra30-devfreq.c b/drivers/devfreq/tegra30-devfreq.c
>>> index a27300f40b0b..5e2b133babdd 100644
>>> --- a/drivers/devfreq/tegra30-devfreq.c
>>> +++ b/drivers/devfreq/tegra30-devfreq.c
>>> @@ -11,6 +11,7 @@
>>>  #include <linux/devfreq.h>
>>>  #include <linux/interrupt.h>
>>>  #include <linux/io.h>
>>> +#include <linux/irq.h>
>>>  #include <linux/module.h>
>>>  #include <linux/mod_devicetable.h>
>>>  #include <linux/platform_device.h>
>>> @@ -416,8 +417,6 @@ static void tegra_actmon_start(struct tegra_devfreq *tegra)
>>>  {
>>>  	unsigned int i;
>>>  
>>> -	disable_irq(tegra->irq);
>>> -
>>>  	actmon_writel(tegra, ACTMON_SAMPLING_PERIOD - 1,
>>>  		      ACTMON_GLB_PERIOD_CTRL);
>>>  
>>> @@ -442,8 +441,6 @@ static void tegra_actmon_stop(struct tegra_devfreq *tegra)
>>>  	}
>>>  
>>>  	actmon_write_barrier(tegra);
>>> -
>>> -	enable_irq(tegra->irq);
>>>  }
>>>  
>>>  static int tegra_devfreq_target(struct device *dev, unsigned long *freq,
>>> @@ -552,6 +549,12 @@ static int tegra_governor_event_handler(struct devfreq *devfreq,
>>>  {
>>>  	struct tegra_devfreq *tegra = dev_get_drvdata(devfreq->dev.parent);
>>>  
>>> +	/*
>>> +	 * Couple device with the governor early as it is needed at
>>> +	 * the moment of governor's start (used by ISR).
>>> +	 */
>>> +	tegra->devfreq = devfreq;
>>
>> I'm not sure it is necessary. Almost devfreq device get
>> the devfreq instance on probe timing through devfreq_add_device directly.
> 
> This is necessary because this assignment is for the "governor" and not
> the "device". Governor is started during of devfreq_add_device(), hence
> there is no better way to assign device to the driver's governor.

OK. I understand.

But, I have a question. Is it working before this patch?
How can you test it on that tegra->devfreq is NULL?

> 
>>> +
>>>  	switch (event) {
>>>  	case DEVFREQ_GOV_START:
>>>  		devfreq_monitor_start(devfreq);
>>> @@ -586,10 +589,11 @@ static struct devfreq_governor tegra_devfreq_governor = {
>>>  
>>>  static int tegra_devfreq_probe(struct platform_device *pdev)
>>>  {
>>> -	struct tegra_devfreq *tegra;
>>>  	struct tegra_devfreq_device *dev;
>>> -	unsigned int i;
>>> +	struct tegra_devfreq *tegra;
>>> +	struct devfreq *devfreq;
>>>  	unsigned long rate;
>>> +	unsigned int i;
>>>  	int err;
>>>  
>>>  	tegra = devm_kzalloc(&pdev->dev, sizeof(*tegra), GFP_KERNEL);
>>> @@ -625,6 +629,16 @@ static int tegra_devfreq_probe(struct platform_device *pdev)
>>>  	}
>>>  	tegra->irq = err;
>>>  
>>> +	irq_set_status_flags(tegra->irq, IRQ_NOAUTOEN);
>>> +
>>> +	err = devm_request_threaded_irq(&pdev->dev, tegra->irq, NULL,
>>> +					actmon_thread_isr, IRQF_ONESHOT,
>>> +					"tegra-devfreq", tegra);
>>> +	if (err) {
>>> +		dev_err(&pdev->dev, "Interrupt request failed: %d\n", err);
>>> +		return err;
>>> +	}
>>> +
>>>  	reset_control_assert(tegra->reset);
>>>  
>>>  	err = clk_prepare_enable(tegra->clock);
>>> @@ -672,28 +686,15 @@ static int tegra_devfreq_probe(struct platform_device *pdev)
>>>  	}
>>>  
>>>  	tegra_devfreq_profile.initial_freq = clk_get_rate(tegra->emc_clock);
>>> -	tegra->devfreq = devfreq_add_device(&pdev->dev,
>>> -					    &tegra_devfreq_profile,
>>> -					    "tegra_actmon",
>>> -					    NULL);
>>> +	devfreq = devfreq_add_device(&pdev->dev, &tegra_devfreq_profile,
>>> +				     "tegra_actmon", NULL);
>>>  	if (IS_ERR(tegra->devfreq)) {
>>
>> Have to check 'devfreq' instead of 'tegra->devfreq'.
>> Did you test it? It might be failed because 'tegra->devfreq is NULL.
> 
> That's a good catch! Thank you very much.
> 
>>>  		err = PTR_ERR(tegra->devfreq);
>>
>> ditto.
> 
> Ok
> 
> 


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics