Message-ID: <20160702013920.GA9796@localhost.localdomain>
Date:	Fri, 1 Jul 2016 18:39:21 -0700
From:	Eduardo Valentin <edubezval@...il.com>
To:	Zhang Rui <rui.zhang@...el.com>
Cc:	Caesar Wang <wxt@...k-chips.com>, linux-pm@...r.kernel.org,
	Heiko Stuebner <heiko@...ech.de>, dianders@...omium.org,
	briannorris@...gle.com, smbarber@...gle.com,
	linux-rockchip@...ts.infradead.org, cf@...k-chips.com,
	huangtao@...k-chips.com, dmitry.torokhov@...il.com,
	javi.merino@....com, peter@...e.net,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Jonathan Corbet <corbet@....net>,
	Andy Champ <andycham@...zon.com>,
	Laxman Dewangan <ldewangan@...dia.com>,
	Durgadoss R <durgadoss.r@...el.com>, Ni Wade <wni@...dia.com>,
	Leo Yan <leo.yan@...aro.org>, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 1/5] thermal: Add support for hardware-tracked trip
 points

On Wed, Jun 22, 2016 at 11:15:19AM +0800, Zhang Rui wrote:
> On 一, 2016-06-06 at 19:44 +0800, Caesar Wang wrote:
> > From: Sascha Hauer <s.hauer@...gutronix.de>
> > 
> > This adds support for hardware-tracked trip points to the device tree
> > thermal sensor framework.
> > 
> > The framework supports an arbitrary number of trip points. Whenever
> > the current temperature is updated, the trip points immediately
> > below and above the current temperature are found. A .set_trips
> > callback is then called with the temperatures. If there is no trip
> > point above or below the current temperature, the passed trip
> > temperature will be -INT_MAX or INT_MAX respectively. In this
> > callback,
> > the driver should program the hardware such that it is notified
> > when either of these trip points are triggered. When a trip point
> > is triggered, the driver should call `thermal_zone_device_update'
> > for the respective thermal zone. This will cause the trip points
> > to be updated again.
> > 
> > If .set_trips is not implemented, the framework behaves as before.
> > 
> > This patch is based on an earlier version from Mikko Perttunen
> > <mikko.perttunen@...si.fi>
> > 
> > Signed-off-by: Sascha Hauer <s.hauer@...gutronix.de>
> > Signed-off-by: Caesar Wang <wxt@...k-chips.com>
> > Cc: Zhang Rui <rui.zhang@...el.com>
> > Cc: Eduardo Valentin <edubezval@...il.com>
> > Cc: linux-pm@...r.kernel.org
> > 
> > ---
> > 
> > Changes in v5:
> > - add the lock for thermal_zone_set_trips function.
> > - change based on next kernel.
> > 
> > Changes in v4:
> > - Missing the lock added in v3.
> > 
> > Changes in v3:
> > - as Javi comments on https://patchwork.kernel.org/patch/9001281/.
> > - add the lock for preventing the called from multi placce
> > - add the note for pre_low/high_trip.
> > 
> > Changes in v2:
> > - update the sysfs-api.txt for set_trips.
> > 
> >  Documentation/thermal/sysfs-api.txt |  7 +++++
> >  drivers/thermal/thermal_core.c      | 54
> > +++++++++++++++++++++++++++++++++++++
> >  drivers/thermal/thermal_sysfs.c     |  3 +++
> >  include/linux/thermal.h             | 10 +++++++
> >  4 files changed, 74 insertions(+)
> > 
> > diff --git a/Documentation/thermal/sysfs-api.txt
> > b/Documentation/thermal/sysfs-api.txt
> > index efc3f3d..75d8838 100644
> > --- a/Documentation/thermal/sysfs-api.txt
> > +++ b/Documentation/thermal/sysfs-api.txt
> > @@ -49,6 +49,9 @@ temperature) and throttle appropriate devices.
> >  	.bind: bind the thermal zone device with a thermal cooling
> > device.
> >  	.unbind: unbind the thermal zone device with a thermal
> > cooling device.
> >  	.get_temp: get the current temperature of the thermal zone.
> > +	.set_trips: set the trip points window. Whenever the current
> > temperature
> > +		    is updated, the trip points immediately below
> > and above the
> > +		    current temperature are found.
> >  	.get_mode: get the current mode (enabled/disabled) of the
> > thermal zone.
> >  	    - "enabled" means the kernel thermal management is
> > enabled.
> >  	    - "disabled" will prevent kernel thermal driver action
> > upon trip points
> > @@ -95,6 +98,10 @@ temperature) and throttle appropriate devices.
> >  			get_temp:	a pointer to a function
> > that reads the
> >  					sensor temperature. This is
> > mandatory
> >  					callback provided by sensor
> > driver.
> > +			set_trips:      a pointer to a function that
> > sets a
> > +					temperature window. When
> > this window is
> > +					left the driver must inform
> > the thermal
> > +					core via
> > thermal_zone_device_update.
> >  			get_trend: 	a pointer to a function
> > that reads the
> >  					sensor temperature trend.
> >  			set_emul_temp:	a pointer to a
> > function that sets
> > diff --git a/drivers/thermal/thermal_core.c
> > b/drivers/thermal/thermal_core.c
> > index 792aab7..e69aee2 100644
> > --- a/drivers/thermal/thermal_core.c
> > +++ b/drivers/thermal/thermal_core.c
> > @@ -368,6 +368,56 @@ static void handle_thermal_trip(struct
> > thermal_zone_device *tz, int trip)
> >  	monitor_thermal_zone(tz);
> >  }
> >  
> > +void thermal_zone_set_trips(struct thermal_zone_device *tz)
> > +{
> > +	int low = -INT_MAX;
> > +	int high = INT_MAX;
> > +	int trip_temp, hysteresis;
> > +	int i, ret;
> > +
> > +	mutex_lock(&tz->lock);
> > +
> > +	if (!tz->ops->set_trips)
> > +		goto exit;
> > +
> 	if (!tz->ops->get_trip_hyst)
> 		goto exit;
> 
> otherwise, the patch looks good to me.

Agreed here, you need to check if get_trip_hyst is present before
calling it. Not all drivers have it.

Besides, I would prefer you to lock after the checks:

	if (!tz->ops->set_trips)
		return;

	if (!tz->ops->get_trip_hyst)
		return;

	mutex_lock(&tz->lock);

> 
> thanks,
> rui
> > +	for (i = 0; i < tz->trips; i++) {
> > +		int trip_low;
> > +
> > +		tz->ops->get_trip_temp(tz, i, &trip_temp);
> > +		tz->ops->get_trip_hyst(tz, i, &hysteresis);
> > +
> > +		trip_low = trip_temp - hysteresis;
> > +
> > +		if (trip_low < tz->temperature && trip_low > low)
> > +			low = trip_low;
> > +
> > +		if (trip_temp > tz->temperature && trip_temp < high)
> > +			high = trip_temp;
> > +	}
> > +
> > +	/* No need to change trip points */
> > +	if (tz->prev_low_trip == low && tz->prev_high_trip == high)
> > +		goto exit;
> > +
> > +	tz->prev_low_trip = low;
> > +	tz->prev_high_trip = high;
> > +
> > +	dev_dbg(&tz->device, "new temperature boundaries: %d < x <
> > %d\n",
> > +			low, high);
> > +
> > +	/*
> > +	 * Set a temperature window. When this window is left the
> > driver
> > +	 * must inform the thermal core via
> > thermal_zone_device_update.
> > +	 */
> > +	ret = tz->ops->set_trips(tz, low, high);
> > +	if (ret)
> > +		dev_err(&tz->device, "Failed to set trips: %d\n",
> > ret);
> > +
> > +exit:
> > +	mutex_unlock(&tz->lock);
> > +}
> > +EXPORT_SYMBOL_GPL(thermal_zone_set_trips);
> > +
> >  static void update_temperature(struct thermal_zone_device *tz)
> >  {
> >  	int temp, ret;
> > @@ -417,6 +467,8 @@ void thermal_zone_device_update(struct
> > thermal_zone_device *tz)
> >  
> >  	update_temperature(tz);
> >  
> > +	thermal_zone_set_trips(tz);
> > +
> >  	for (count = 0; count < tz->trips; count++)
> >  		handle_thermal_trip(tz, count);
> >  }
> > @@ -1175,6 +1227,8 @@ thermal_zone_device_register(const char *type,
> > int trips, int mask,
> >  	tz->trips = trips;
> >  	tz->passive_delay = passive_delay;
> >  	tz->polling_delay = polling_delay;
> > +	tz->prev_low_trip = INT_MAX;
> > +	tz->prev_high_trip = -INT_MAX;
> >  
> >  	/* sys I/F */
> >  	/* Add nodes that are always present via .groups */
> > diff --git a/drivers/thermal/thermal_sysfs.c
> > b/drivers/thermal/thermal_sysfs.c
> > index 743df50..33bbe30 100644
> > --- a/drivers/thermal/thermal_sysfs.c
> > +++ b/drivers/thermal/thermal_sysfs.c
> > @@ -219,6 +219,9 @@ trip_point_hyst_store(struct device *dev, struct
> > device_attribute *attr,
> >  	ret = tz->ops->set_trip_hyst(tz, trip, temperature);
> >  	mutex_unlock(&tz->lock);
> >  
> > +	if (!ret)
> > +		thermal_zone_set_trips(tz);
> > +
> >  	return ret ? ret : count;
> >  }
> >  
> > diff --git a/include/linux/thermal.h b/include/linux/thermal.h
> > index ea667b6..780e69d 100644
> > --- a/include/linux/thermal.h
> > +++ b/include/linux/thermal.h
> > @@ -99,6 +99,7 @@ struct thermal_zone_device_ops {
> >  	int (*unbind) (struct thermal_zone_device *,
> >  		       struct thermal_cooling_device *);
> >  	int (*get_temp) (struct thermal_zone_device *, int *);
> > +	int (*set_trips) (struct thermal_zone_device *, int, int);
> >  	int (*get_mode) (struct thermal_zone_device *,
> >  			 enum thermal_device_mode *);
> >  	int (*set_mode) (struct thermal_zone_device *,
> > @@ -169,6 +170,10 @@ struct thermal_attr {
> >   * @last_temperature:	previous temperature read
> >   * @emul_temperature:	emulated temperature when using
> > CONFIG_THERMAL_EMULATION
> >   * @passive:		1 if you've crossed a passive trip
> > point, 0 otherwise.
> > + * @prev_low_trip:	the low current temperature if you've
> > crossed a passive
> > +			trip point.
> > + * @prev_high_trip:	the above current temperature if you've
> > crossed a
> > +			passive trip point.
> >   * @forced_passive:	If > 0, temperature at which to switch on
> > all ACPI
> >   *			processor cooling devices.  Currently only
> > used by the
> >   *			step-wise governor.
> > @@ -201,6 +206,8 @@ struct thermal_zone_device {
> >  	int last_temperature;
> >  	int emul_temperature;
> >  	int passive;
> > +	int prev_low_trip;
> > +	int prev_high_trip;
> >  	unsigned int forced_passive;
> >  	atomic_t need_update;
> >  	struct thermal_zone_device_ops *ops;
> > @@ -428,6 +435,7 @@ int thermal_zone_bind_cooling_device(struct
> > thermal_zone_device *, int,
> >  int thermal_zone_unbind_cooling_device(struct thermal_zone_device *,
> > int,
> >  				       struct thermal_cooling_device
> > *);
> >  void thermal_zone_device_update(struct thermal_zone_device *);
> > +void thermal_zone_set_trips(struct thermal_zone_device *);
> >  
> >  struct thermal_cooling_device *thermal_cooling_device_register(char
> > *, void *,
> >  		const struct thermal_cooling_device_ops *);
> > @@ -477,6 +485,8 @@ static inline int
> > thermal_zone_unbind_cooling_device(
> >  { return -ENODEV; }
> >  static inline void thermal_zone_device_update(struct
> > thermal_zone_device *tz)
> >  { }
> > +static inline void thermal_zone_set_trips(struct thermal_zone_device
> > *tz)
> > +{ }
> >  static inline struct thermal_cooling_device *
> >  thermal_cooling_device_register(char *type, void *devdata,
> >  	const struct thermal_cooling_device_ops *ops)

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