Re: [PATCH v2 10/19] PM / devfreq: tegra: Drop primary interrupt handler

[Chanwoo Choi]

Hi,

It looks good to me to drop the primary interrupt handler
but I have some comments. Please check it.

On 19. 4. 15. ìí 11:54, Dmitry Osipenko wrote:
> There is no real need in the primary interrupt handler, hence move
> everything to the secondary (threaded) handler. In a result locking
> is consistent now and there are no potential races with the interrupt
> handler because it is protected with the devfreq's mutex.
> 
> Signed-off-by: Dmitry Osipenko <digetx@xxxxxxxxx>
> ---
>  drivers/devfreq/tegra-devfreq.c | 61 ++++++++++++---------------------
>  1 file changed, 22 insertions(+), 39 deletions(-)
> 
> diff --git a/drivers/devfreq/tegra-devfreq.c b/drivers/devfreq/tegra-devfreq.c
> index 2a1464098200..69b557df5084 100644
> --- a/drivers/devfreq/tegra-devfreq.c
> +++ b/drivers/devfreq/tegra-devfreq.c
> @@ -144,7 +144,6 @@ static struct tegra_devfreq_device_config actmon_device_configs[] = {
>  struct tegra_devfreq_device {
>  	const struct tegra_devfreq_device_config *config;
>  	void __iomem *regs;
> -	spinlock_t lock;
>  
>  	/* Average event count sampled in the last interrupt */
>  	u32 avg_count;
> @@ -249,11 +248,8 @@ static void actmon_write_barrier(struct tegra_devfreq *tegra)
>  static void actmon_isr_device(struct tegra_devfreq *tegra,
>  			      struct tegra_devfreq_device *dev)
>  {
> -	unsigned long flags;
>  	u32 intr_status, dev_ctrl;
>  
> -	spin_lock_irqsave(&dev->lock, flags);
> -
>  	dev->avg_count = device_readl(dev, ACTMON_DEV_AVG_COUNT);
>  	tegra_devfreq_update_avg_wmark(tegra, dev);
>  
> @@ -302,26 +298,6 @@ static void actmon_isr_device(struct tegra_devfreq *tegra,
>  	device_writel(dev, ACTMON_INTR_STATUS_CLEAR, ACTMON_DEV_INTR_STATUS);
>  
>  	actmon_write_barrier(tegra);
> -
> -	spin_unlock_irqrestore(&dev->lock, flags);
> -}
> -
> -static irqreturn_t actmon_isr(int irq, void *data)
> -{
> -	struct tegra_devfreq *tegra = data;
> -	bool handled = false;
> -	unsigned int i;
> -	u32 val;
> -
> -	val = actmon_readl(tegra, ACTMON_GLB_STATUS);
> -	for (i = 0; i < ARRAY_SIZE(tegra->devices); i++) {
> -		if (val & tegra->devices[i].config->irq_mask) {
> -			actmon_isr_device(tegra, tegra->devices + i);
> -			handled = true;
> -		}
> -	}
> -
> -	return handled ? IRQ_WAKE_THREAD : IRQ_NONE;
>  }
>  
>  static unsigned long actmon_cpu_to_emc_rate(struct tegra_devfreq *tegra,
> @@ -348,35 +324,46 @@ static void actmon_update_target(struct tegra_devfreq *tegra,
>  	unsigned long cpu_freq = 0;
>  	unsigned long static_cpu_emc_freq = 0;
>  	unsigned int avg_sustain_coef;
> -	unsigned long flags;
> +	u32 avg_count;
>  
>  	if (dev->config->avg_dependency_threshold) {
>  		cpu_freq = cpufreq_get(0);
>  		static_cpu_emc_freq = actmon_cpu_to_emc_rate(tegra, cpu_freq);
>  	}
>  
> -	spin_lock_irqsave(&dev->lock, flags);
> -
> -	dev->target_freq = dev->avg_count / ACTMON_SAMPLING_PERIOD;
> +	avg_count = dev->avg_count;
> +	dev->target_freq = avg_count / ACTMON_SAMPLING_PERIOD;

Actually, this change is not related to this patch.
Please keep the original code.

>  	avg_sustain_coef = 100 * 100 / dev->config->boost_up_threshold;
>  	dev->target_freq = do_percent(dev->target_freq, avg_sustain_coef);
>  	dev->target_freq += dev->boost_freq;
>  
> -	if (dev->avg_count >= dev->config->avg_dependency_threshold)
> +	if (avg_count >= dev->config->avg_dependency_threshold)

ditto.

>  		dev->target_freq = max(dev->target_freq, static_cpu_emc_freq);
> -
> -	spin_unlock_irqrestore(&dev->lock, flags);
>  }
>  
>  static irqreturn_t actmon_thread_isr(int irq, void *data)
>  {
>  	struct tegra_devfreq *tegra = data;
> +	bool handled = false;
> +	unsigned int i;
> +	u32 val;
>  
>  	mutex_lock(&tegra->devfreq->lock);
> -	update_devfreq(tegra->devfreq);
> +
> +	val = actmon_readl(tegra, ACTMON_GLB_STATUS);
> +	for (i = 0; i < ARRAY_SIZE(tegra->devices); i++) {
> +		if (val & tegra->devices[i].config->irq_mask) {
> +			actmon_isr_device(tegra, tegra->devices + i);
> +			handled = true;
> +		}
> +	}
> +
> +	if (handled)
> +		update_devfreq(tegra->devfreq);
> +
>  	mutex_unlock(&tegra->devfreq->lock);
>  
> -	return IRQ_HANDLED;
> +	return handled ? IRQ_HANDLED : IRQ_NONE;
>  }
>  
>  static int tegra_actmon_rate_notify_cb(struct notifier_block *nb,
> @@ -386,7 +373,6 @@ static int tegra_actmon_rate_notify_cb(struct notifier_block *nb,
>  	struct tegra_devfreq *tegra;
>  	struct tegra_devfreq_device *dev;
>  	unsigned int i;
> -	unsigned long flags;
>  
>  	if (action != POST_RATE_CHANGE)
>  		return NOTIFY_OK;
> @@ -398,9 +384,7 @@ static int tegra_actmon_rate_notify_cb(struct notifier_block *nb,

When I review this patch, I have a question
about why tegra_actmon_rate_notify_cb is needed.

tegra_actmon_rate_notify_cb() do something
when the clock rate of emc_clock is changed.
I think that 'emc_clock' is changed by this driver.
It means that the this driver can catch the change timing
of emc_clock rate without notifier. 

IMO, it is possible to call tegra_devfreq_update_wmark()
directly without clock notifier before calling
'clk_set_min_rate()/clk_set_rate()' in the tegra_devfreq_target().

With clock notifier, it cannot restore something for
tegra_devfreq_update_wmark(tegra, dev) when failed to
set the rate of emc_clk by 'clk_set_min_rate()/clk_set_rate()'.

>  	for (i = 0; i < ARRAY_SIZE(tegra->devices); i++) {
>  		dev = &tegra->devices[i];
>  
> -		spin_lock_irqsave(&dev->lock, flags);
>  		tegra_devfreq_update_wmark(tegra, dev);
> -		spin_unlock_irqrestore(&dev->lock, flags);
>  	}
>  
>  	actmon_write_barrier(tegra);
> @@ -668,7 +652,6 @@ static int tegra_devfreq_probe(struct platform_device *pdev)
>  		dev = tegra->devices + i;
>  		dev->config = actmon_device_configs + i;
>  		dev->regs = tegra->regs + dev->config->offset;
> -		spin_lock_init(&dev->lock);
>  
>  		tegra_actmon_configure_device(tegra, dev);
>  	}
> @@ -696,8 +679,8 @@ static int tegra_devfreq_probe(struct platform_device *pdev)
>  		return err;
>  	}
>  
> -	err = devm_request_threaded_irq(&pdev->dev, irq, actmon_isr,
> -					actmon_thread_isr, IRQF_SHARED,
> +	err = devm_request_threaded_irq(&pdev->dev, irq, NULL,
> +					actmon_thread_isr, IRQF_ONESHOT,
>  					"tegra-devfreq", tegra);
>  	if (err) {
>  		dev_err(&pdev->dev, "Interrupt request failed\n");
> 


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics