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path: root/drivers/thermal/gov_bang_bang.c
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2016-09-27thermal: bang-bang governor: act on lower trip boundarySascha Hauer1-1/+1
With interrupt driven thermal zones we pass the lower and upper temperature on which shall be acted, so in the governor we have to act on the exact lower temperature to be consistent. Otherwise an interrupt maybe generated on the exact lower temperature, but the bang bang governor does not react since The polling driven zones have to be one step cooler before the governor reacts. Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de> Signed-off-by: Caesar Wang <wxt@rock-chips.com> Cc: Zhang Rui <rui.zhang@intel.com> Cc: Eduardo Valentin <edubezval@gmail.com> Cc: linux-pm@vger.kernel.org Acked-by: Peter Feuerer <peter@piie.net> Signed-off-by: Eduardo Valentin <edubezval@gmail.com> Signed-off-by: Zhang Rui <rui.zhang@intel.com>
2016-08-08thermal: fix race condition when updating cooling deviceMichele Di Giorgio1-0/+2
When multiple thermal zones are bound to the same cooling device, multiple kernel threads may want to update the cooling device state by calling thermal_cdev_update(). Having cdev not protected by a mutex can lead to a race condition. Consider the following situation with two kernel threads k1 and k2: Thread k1 Thread k2 || || call thermal_cdev_update() || ... || set_cur_state(cdev, target); call power_actor_set_power() || ... || instance->target = state; || cdev->updated = false; || || cdev->updated = true; || // completes execution call thermal_cdev_update() || // cdev->updated == true || return; || \/ time k2 has already looped through the thermal instances looking for the deepest cooling device state and is preempted right before setting cdev->updated to true. Now, k1 runs, modifies the thermal instance state and sets cdev->updated to false. Then, k1 is preempted and k2 continues the execution by setting cdev->updated to true, therefore preventing k1 from performing the update. Notice that this is not an issue if k2 looks at the instance->target modified by k1 "after" it is assigned by k1. In fact, in this case the update will happen anyway and k1 can safely return immediately from thermal_cdev_update(). This may lead to a situation where a thermal governor never updates the cooling device. For example, this is the case for the step_wise governor: when calling the function thermal_zone_trip_update(), the governor may always get a new state equal to the old one (which, however, wasn't notified to the cooling device) and will therefore skip the update. CC: Zhang Rui <rui.zhang@intel.com> CC: Eduardo Valentin <edubezval@gmail.com> CC: Peter Feuerer <peter@piie.net> Reported-by: Toby Huang <toby.huang@arm.com> Signed-off-by: Michele Di Giorgio <michele.digiorgio@arm.com> Reviewed-by: Javi Merino <javi.merino@arm.com> Signed-off-by: Zhang Rui <rui.zhang@intel.com>
2016-05-16thermal: check validity get_trip_hyst function pointer in bang-bang governorMichele Di Giorgio1-1/+7
Bang-bang thermal governor uses trip point hysteresis to make decisions. Hysteresis is a required property in the device tree for trip points, but it is an optional thermal zone device operation. Hence, we need to check whether the function pointer is valid or not. If it is not available, we assume the hysteresis to be zero. Consequently, a highly varying temperature will make the governor continuosly switch a cooling device ON and OFF. CC: Zhang Rui <rui.zhang@intel.com> CC: Eduardo Valentin <edubezval@gmail.com> CC: Peter Feuerer <peter@piie.net> Signed-off-by: Michele Di Giorgio <michele.digiorgio@arm.com> Signed-off-by: Zhang Rui <rui.zhang@intel.com>
2015-08-03thermal: consistently use int for temperaturesSascha Hauer1-3/+2
The thermal code uses int, long and unsigned long for temperatures in different places. Using an unsigned type limits the thermal framework to positive temperatures without need. Also several drivers currently will report temperatures near UINT_MAX for temperatures below 0°C. This will probably immediately shut the machine down due to overtemperature if started below 0°C. 'long' is 64bit on several architectures. This is not needed since INT_MAX °mC is above the melting point of all known materials. Consistently use a plain 'int' for temperatures throughout the thermal code and the drivers. This only changes the places in the drivers where the temperature is passed around as pointer, when drivers internally use another type this is not changed. Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de> Acked-by: Geert Uytterhoeven <geert+renesas@glider.be> Reviewed-by: Jean Delvare <jdelvare@suse.de> Reviewed-by: Lukasz Majewski <l.majewski@samsung.com> Reviewed-by: Darren Hart <dvhart@linux.intel.com> Reviewed-by: Heiko Stuebner <heiko@sntech.de> Reviewed-by: Peter Feuerer <peter@piie.net> Cc: Punit Agrawal <punit.agrawal@arm.com> Cc: Zhang Rui <rui.zhang@intel.com> Cc: Eduardo Valentin <edubezval@gmail.com> Cc: linux-pm@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: Jean Delvare <jdelvare@suse.de> Cc: Peter Feuerer <peter@piie.net> Cc: Heiko Stuebner <heiko@sntech.de> Cc: Lukasz Majewski <l.majewski@samsung.com> Cc: Stephen Warren <swarren@wwwdotorg.org> Cc: Thierry Reding <thierry.reding@gmail.com> Cc: linux-acpi@vger.kernel.org Cc: platform-driver-x86@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-omap@vger.kernel.org Cc: linux-samsung-soc@vger.kernel.org Cc: Guenter Roeck <linux@roeck-us.net> Cc: Rafael J. Wysocki <rjw@rjwysocki.net> Cc: Maxime Ripard <maxime.ripard@free-electrons.com> Cc: Darren Hart <dvhart@infradead.org> Cc: lm-sensors@lm-sensors.org Signed-off-by: Zhang Rui <rui.zhang@intel.com>
2014-08-27thermal: Added Bang-bang thermal governorPeter Feuerer1-0/+131
The bang-bang thermal governor uses a hysteresis to switch abruptly on or off a cooling device. It is intended to control fans, which can not be throttled but just switched on or off. Bang-bang cannot be set as default governor as it is intended for special devices only. For those special devices the driver needs to explicitely request it. Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Zhang Rui <rui.zhang@intel.com> Cc: Andreas Mohr <andi@lisas.de> Cc: Borislav Petkov <bp@suse.de> Cc: Javi Merino <javi.merino@arm.com> Cc: linux-pm@vger.kernel.org Signed-off-by: Peter Feuerer <peter@piie.net> Signed-off-by: Zhang Rui <rui.zhang@intel.com>