Date:   Sat, 2 Sep 2017 11:29:24 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     rui.zhang@...el.com, edubezval@...il.com, linux-pm@...r.kernel.org,
        kevin.wangtao@...aro.org, open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 09/13] thermal/drivers/hisi: Remove costly sensor
 inspection

On Wed, Aug 30, 2017 at 10:47:33AM +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.
> 
> Signed-off-by: Daniel Lezcano <daniel.lezcano@...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 3e03908..b038d8a 100644
> --- a/drivers/thermal/hisi_thermal.c
> +++ b/drivers/thermal/hisi_thermal.c
> @@ -39,6 +39,7 @@
>  #define HISI_TEMP_BASE			(-60000)
>  #define HISI_TEMP_RESET			(100000)
>  #define HISI_TEMP_STEP			(784)
> +#define HISI_TEMP_LAG			(3500)

So I am curious what's the reason to select 3.5'c for lag value? Is
this a heuristics result?

>  #define HISI_MAX_SENSORS		4
>  #define HISI_DEFAULT_SENSOR		2
> @@ -58,8 +59,6 @@ struct hisi_thermal_data {
>  	struct clk *clk;
>  	struct hisi_thermal_sensor sensors;
>  	int irq;
> -	bool irq_enabled;
> -	
>  	void __iomem *regs;
>  };
>  
> @@ -97,9 +96,40 @@ 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.

So here means if we set a long lag value and the interrupt is delayed,
sometimes we even don't receive the interrupt; but this is acceptable
due we are polling the temperature so we still can get the updated
temperature value, right?

> + *
> + * [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)
> @@ -167,71 +197,6 @@ static inline void hisi_thermal_hdak_set(void __iomem *addr, int value)
>  	writel(readl(addr + TEMP0_CFG) | (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);
> @@ -249,25 +214,10 @@ 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;
>  }
> @@ -276,26 +226,27 @@ 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);
> +	}

For temperature increasing and decreasing both cases, can always call
thermal_zone_device_update()?

>  
>  	return IRQ_HANDLED;
>  }
> @@ -348,6 +299,40 @@ 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;
> @@ -390,9 +375,6 @@ 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);
> @@ -402,18 +384,21 @@ 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;
>  }
> @@ -436,7 +421,6 @@ 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);
>  
> @@ -452,8 +436,7 @@ 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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