Message-ID: <20170908032227.GE2755@localhost.localdomain>
Date:   Thu, 7 Sep 2017 20:22:29 -0700
From:   Eduardo Valentin <edubezval@...il.com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     rui.zhang@...el.com, linux-pm@...r.kernel.org,
        kevin.wangtao@...aro.org, leo.yan@...aro.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 09/13] thermal/drivers/hisi: Remove costly sensor
 inspection

On Mon, Sep 04, 2017 at 09:56:08PM +0200, Daniel Lezcano wrote:
> The sensor is all setup, bind, resetted, acked, etc... every single second.
> 
> That was the way to workaround a problem with the interrupt bouncing again and
> again.
> 
> With the following changes, we fix all in one:
> 
>  - Do the setup, one time, at probe time
> 
>  - Add the IRQF_ONESHOT, ack the interrupt in the threaded handler
> 
>  - Remove the interrupt handler
> 
>  - Set the correct value for the LAG register
> 
>  - Remove all the irq_enabled stuff in the code as the interruption
>    handling is fixed
> 
>  - Remove the 3ms delay
> 
>  - Reorder the initialization routine to be in the right order
> 
> It ends up to a nicer code and more efficient, the 3-5ms delay is removed from
> the get_temp() path.

It would be good if you could include in your commit message why before
the 3-5ms was needed and now you dont need it. These delays are typical
on ADC conversion time in order to get the proper temperature read. One
side effect of removing the delay could be that you would be caching
previously converted value stored in the register interface, which,
depending on your policy and polling setup, could be bad. Say you have a
polling setup for 1s, you would wait 2s to see read temperature, which,
depending on how the zone behaves could be enough to miss a spike.

> 
> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> Reviewed-by: Leo Yan <leo.yan@...aro.org>
> Tested-by: Leo Yan <leo.yan@...aro.org>
> ---
>  drivers/thermal/hisi_thermal.c | 203 +++++++++++++++++++----------------------
>  1 file changed, 93 insertions(+), 110 deletions(-)
> 
> diff --git a/drivers/thermal/hisi_thermal.c b/drivers/thermal/hisi_thermal.c
> index 10ef6bc..3ce9a4f 100644
> --- a/drivers/thermal/hisi_thermal.c
> +++ b/drivers/thermal/hisi_thermal.c
> @@ -41,6 +41,7 @@
>  #define HISI_TEMP_BASE			(-60000)
>  #define HISI_TEMP_RESET			(100000)
>  #define HISI_TEMP_STEP			(784)
> +#define HISI_TEMP_LAG			(3500)
>  
>  #define HISI_MAX_SENSORS		4
>  #define HISI_DEFAULT_SENSOR		2
> @@ -60,8 +61,6 @@ struct hisi_thermal_data {
>  	struct clk *clk;
>  	struct hisi_thermal_sensor sensors;
>  	int irq;
> -	bool irq_enabled;
> -
>  	void __iomem *regs;
>  };
>  
> @@ -99,9 +98,40 @@ static inline long hisi_thermal_round_temp(int temp)
>  		hisi_thermal_temp_to_step(temp));
>  }
>  
> +/*
> + * The lag register contains 5 bits encoding the temperature in steps.
> + *
> + * Each time the temperature crosses the threshold boundary, an
> + * interrupt is raised. It could be when the temperature is going
> + * above the threshold or below. However, if the temperature is
> + * fluctuating around this value due to the load, we can receive
> + * several interrupts which may not desired.
> + *
> + * We can setup a temperature representing the delta between the
> + * threshold and the current temperature when the temperature is
> + * decreasing.
> + *
> + * For instance: the lag register is 5°C, the threshold is 65°C, when
> + * the temperature reaches 65°C an interrupt is raised and when the
> + * temperature decrease to 65°C - 5°C another interrupt is raised.
> + *
> + * A very short lag can lead to an interrupt storm, a long lag
> + * increase the latency to react to the temperature changes.  In our
> + * case, that is not really a problem as we are polling the
> + * temperature.
> + *
> + * [0:4] : lag register
> + *
> + * The temperature is coded in steps, cf. HISI_TEMP_STEP.
> + *
> + * Min : 0x00 :  0.0 °C
> + * Max : 0x1F : 24.3 °C
> + *
> + * The 'value' parameter is in milliCelsius.
> + */
>  static inline void hisi_thermal_set_lag(void __iomem *addr, int value)
>  {
> -	writel(value, addr + TEMP0_LAG);
> +	writel((value / HISI_TEMP_STEP) & 0x1F, addr + TEMP0_LAG);
>  }
>  
>  static inline void hisi_thermal_alarm_clear(void __iomem *addr, int value)
> @@ -171,71 +201,6 @@ static inline void hisi_thermal_hdak_set(void __iomem *addr, int value)
>  	       (value << 4), addr + TEMP0_CFG);
>  }
>  
> -static long hisi_thermal_get_sensor_temp(struct hisi_thermal_data *data,
> -					 struct hisi_thermal_sensor *sensor)
> -{
> -	long val;
> -
> -	mutex_lock(&data->thermal_lock);
> -
> -	/* disable interrupt */
> -	hisi_thermal_alarm_enable(data->regs, 0);
> -	hisi_thermal_alarm_clear(data->regs, 1);
> -
> -	/* disable module firstly */
> -	hisi_thermal_enable(data->regs, 0);
> -
> -	/* select sensor id */
> -	hisi_thermal_sensor_select(data->regs, sensor->id);
> -
> -	/* enable module */
> -	hisi_thermal_enable(data->regs, 1);
> -
> -	usleep_range(3000, 5000);
> -
> -	val = hisi_thermal_get_temperature(data->regs);
> -
> -	mutex_unlock(&data->thermal_lock);
> -
> -	return val;
> -}
> -
> -static void hisi_thermal_enable_bind_irq_sensor
> -			(struct hisi_thermal_data *data)
> -{
> -	struct hisi_thermal_sensor *sensor;
> -
> -	mutex_lock(&data->thermal_lock);
> -
> -	sensor = &data->sensors;
> -
> -	/* setting the hdak time */
> -	hisi_thermal_hdak_set(data->regs, 0);
> -
> -	/* disable module firstly */
> -	hisi_thermal_reset_enable(data->regs, 0);
> -	hisi_thermal_enable(data->regs, 0);
> -
> -	/* select sensor id */
> -	hisi_thermal_sensor_select(data->regs, sensor->id);
> -
> -	/* enable for interrupt */
> -	hisi_thermal_alarm_set(data->regs, sensor->thres_temp);
> -
> -	hisi_thermal_reset_set(data->regs, HISI_TEMP_RESET);
> -
> -	/* enable module */
> -	hisi_thermal_reset_enable(data->regs, 1);
> -	hisi_thermal_enable(data->regs, 1);
> -
> -	hisi_thermal_alarm_clear(data->regs, 0);
> -	hisi_thermal_alarm_enable(data->regs, 1);
> -
> -	usleep_range(3000, 5000);
> -
> -	mutex_unlock(&data->thermal_lock);
> -}
> -
>  static void hisi_thermal_disable_sensor(struct hisi_thermal_data *data)
>  {
>  	mutex_lock(&data->thermal_lock);
> @@ -253,25 +218,10 @@ static int hisi_thermal_get_temp(void *_sensor, int *temp)
>  	struct hisi_thermal_sensor *sensor = _sensor;
>  	struct hisi_thermal_data *data = sensor->thermal;
>  
> -	*temp = hisi_thermal_get_sensor_temp(data, sensor);
> -
> -	dev_dbg(&data->pdev->dev, "id=%d, irq=%d, temp=%d, thres=%d\n",
> -		sensor->id, data->irq_enabled, *temp, sensor->thres_temp);
> -	/*
> -	 * Bind irq to sensor for two cases:
> -	 *   Reenable alarm IRQ if temperature below threshold;
> -	 *   if irq has been enabled, always set it;
> -	 */
> -	if (data->irq_enabled) {
> -		hisi_thermal_enable_bind_irq_sensor(data);
> -		return 0;
> -	}
> +	*temp = hisi_thermal_get_temperature(data->regs);
>  
> -	if (*temp < sensor->thres_temp) {
> -		data->irq_enabled = true;
> -		hisi_thermal_enable_bind_irq_sensor(data);
> -		enable_irq(data->irq);
> -	}
> +	dev_dbg(&data->pdev->dev, "id=%d, temp=%d, thres=%d\n",
> +		sensor->id, *temp, sensor->thres_temp);
>  
>  	return 0;
>  }
> @@ -280,26 +230,27 @@ static const struct thermal_zone_of_device_ops hisi_of_thermal_ops = {
>  	.get_temp = hisi_thermal_get_temp,
>  };
>  
> -static irqreturn_t hisi_thermal_alarm_irq(int irq, void *dev)
> +static irqreturn_t hisi_thermal_alarm_irq_thread(int irq, void *dev)
>  {
>  	struct hisi_thermal_data *data = dev;
> +	struct hisi_thermal_sensor *sensor = &data->sensors;
> +	int temp;
>  
> -	disable_irq_nosync(irq);
> -	data->irq_enabled = false;
> +	hisi_thermal_alarm_clear(data->regs, 1);
>  
> -	return IRQ_WAKE_THREAD;
> -}
> +	temp = hisi_thermal_get_temperature(data->regs);
>  
> -static irqreturn_t hisi_thermal_alarm_irq_thread(int irq, void *dev)
> -{
> -	struct hisi_thermal_data *data = dev;
> -	struct hisi_thermal_sensor *sensor = &data->sensors;
> +	if (temp >= sensor->thres_temp) {
> +		dev_crit(&data->pdev->dev, "THERMAL ALARM: %d > %d\n",
> +			 temp, sensor->thres_temp);
>  
> -	dev_crit(&data->pdev->dev, "THERMAL ALARM: T > %d\n",
> -		 sensor->thres_temp);
> +		thermal_zone_device_update(data->sensors.tzd,
> +					   THERMAL_EVENT_UNSPECIFIED);
>  
> -	thermal_zone_device_update(data->sensors.tzd,
> -				   THERMAL_EVENT_UNSPECIFIED);
> +	} else if (temp < sensor->thres_temp) {
> +		dev_crit(&data->pdev->dev, "THERMAL ALARM stopped: %d < %d\n",
> +			 temp, sensor->thres_temp);
> +	}
>  
>  	return IRQ_HANDLED;
>  }
> @@ -352,6 +303,40 @@ static void hisi_thermal_toggle_sensor(struct hisi_thermal_sensor *sensor,
>  		on ? THERMAL_DEVICE_ENABLED : THERMAL_DEVICE_DISABLED);
>  }
>  
> +static int hisi_thermal_setup(struct hisi_thermal_data *data)
> +{
> +	struct hisi_thermal_sensor *sensor;
> +
> +	sensor = &data->sensors;
> +
> +	/* disable module firstly */
> +	hisi_thermal_reset_enable(data->regs, 0);
> +	hisi_thermal_enable(data->regs, 0);
> +
> +	/* select sensor id */
> +	hisi_thermal_sensor_select(data->regs, sensor->id);
> +
> +	/* setting the hdak time */
> +	hisi_thermal_hdak_set(data->regs, 0);
> +
> +	/* setting lag value between current temp and the threshold */
> +	hisi_thermal_set_lag(data->regs, HISI_TEMP_LAG);
> +
> +	/* enable for interrupt */
> +	hisi_thermal_alarm_set(data->regs, sensor->thres_temp);
> +
> +	hisi_thermal_reset_set(data->regs, HISI_TEMP_RESET);
> +
> +	/* enable module */
> +	hisi_thermal_reset_enable(data->regs, 1);
> +	hisi_thermal_enable(data->regs, 1);
> +
> +	hisi_thermal_alarm_clear(data->regs, 0);
> +	hisi_thermal_alarm_enable(data->regs, 1);
> +
> +	return 0;
> +}
> +
>  static int hisi_thermal_probe(struct platform_device *pdev)
>  {
>  	struct hisi_thermal_data *data;
> @@ -394,9 +379,6 @@ static int hisi_thermal_probe(struct platform_device *pdev)
>  		return ret;
>  	}
>  
> -	hisi_thermal_enable_bind_irq_sensor(data);
> -	data->irq_enabled = true;
> -
>  	ret = hisi_thermal_register_sensor(pdev, data,
>  					   &data->sensors,
>  					   HISI_DEFAULT_SENSOR);
> @@ -406,18 +388,21 @@ static int hisi_thermal_probe(struct platform_device *pdev)
>  		return ret;
>  	}
>  
> -	hisi_thermal_toggle_sensor(&data->sensors, true);
> +	ret = hisi_thermal_setup(data);
> +	if (ret) {
> +		dev_err(&pdev->dev, "Failed to setup the sensor: %d\n", ret);
> +		return ret;
> +	}
>  
> -	ret = devm_request_threaded_irq(&pdev->dev, data->irq,
> -					hisi_thermal_alarm_irq,
> +	ret = devm_request_threaded_irq(&pdev->dev, data->irq, NULL,
>  					hisi_thermal_alarm_irq_thread,
> -					0, "hisi_thermal", data);
> +					IRQF_ONESHOT, "hisi_thermal", data);
>  	if (ret < 0) {
>  		dev_err(&pdev->dev, "failed to request alarm irq: %d\n", ret);
>  		return ret;
>  	}
>  
> -	enable_irq(data->irq);
> +	hisi_thermal_toggle_sensor(&data->sensors, true);
>  
>  	return 0;
>  }
> @@ -440,7 +425,6 @@ static int hisi_thermal_suspend(struct device *dev)
>  	struct hisi_thermal_data *data = dev_get_drvdata(dev);
>  
>  	hisi_thermal_disable_sensor(data);
> -	data->irq_enabled = false;
>  
>  	clk_disable_unprepare(data->clk);
>  
> @@ -456,8 +440,7 @@ static int hisi_thermal_resume(struct device *dev)
>  	if (ret)
>  		return ret;
>  
> -	data->irq_enabled = true;
> -	hisi_thermal_enable_bind_irq_sensor(data);
> +	hisi_thermal_setup(data);
>  
>  	return 0;
>  }
> -- 
> 2.7.4
> 

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