• Amit Daniel Kachhap's avatar
    thermal: add generic cpufreq cooling implementation · 02361418
    Amit Daniel Kachhap authored
    This patchset introduces a new generic cooling device based on cpufreq
    that can be used on non-ACPI platforms.  As a proof of concept, we have
    drivers for the following platforms using this mechanism now:
    
     * Samsung Exynos (Exynos4 and Exynos5) in the current patchset.
     * Freescale i.MX (git://git.linaro.org/people/amitdanielk/linux.git imx6q_thermal)
    
    There is a small change in cpufreq cooling registration APIs, so a minor
    change is needed for Freescale platforms.
    
    Brief Description:
    
    1) The generic cooling devices code is placed inside driver/thermal/*
       as placing inside acpi folder will need un-necessary enabling of acpi
       code.  This code is architecture independent.
    
    2) This patchset adds generic cpu cooling low level implementation
       through frequency clipping.  In future, other cpu related cooling
       devices may be added here.  An ACPI version of this already exists
       (drivers/acpi/processor_thermal.c) .But this will be useful for
       platforms like ARM using the generic thermal interface along with the
       generic cpu cooling devices.  The cooling device registration API's
       return cooling device pointers which can be easily binded with the
       thermal zone trip points.  The important APIs exposed are,
    
       a) struct thermal_cooling_device *cpufreq_cooling_register(
            struct cpumask *clip_cpus)
       b) void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev)
    
    3) Samsung exynos platform thermal implementation is done using the
       generic cpu cooling APIs and the new trip type.  The temperature sensor
       driver present in the hwmon folder(registered as hwmon driver) is moved
       to thermal folder and registered as a thermal driver.
    
    A simple data/control flow diagrams is shown below,
    
    Core Linux thermal <----->  Exynos thermal interface <----- Temperature Sensor
              |                             |
             \|/                            |
      Cpufreq cooling device <---------------
    
    TODO:
    *Will send the DT enablement patches later after the driver is merged.
    
    This patch:
    
    Add support for generic cpu thermal cooling low level implementations
    using frequency scaling up/down based on the registration parameters.
    Different cpu related cooling devices can be registered by the user and
    the binding of these cooling devices to the corresponding trip points can
    be easily done as the registration APIs return the cooling device pointer.
    The user of these APIs are responsible for passing clipping frequency .
    The drivers can also register to recieve notification about any cooling
    action called.
    
    [akpm@linux-foundation.org: fix comment layout]
    Signed-off-by: default avatarAmit Daniel Kachhap <amit.kachhap@linaro.org>
    Cc: Guenter Roeck <guenter.roeck@ericsson.com>
    Cc: SangWook Ju <sw.ju@samsung.com>
    Cc: Durgadoss <durgadoss.r@intel.com>
    Cc: Len Brown <lenb@kernel.org>
    Cc: Jean Delvare <khali@linux-fr.org>
    Cc: Kyungmin Park <kmpark@infradead.org>
    Cc: Kukjin Kim <kgene.kim@samsung.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarAmit Daniel Kachhap <amit.daniel@samsung.com>
    Signed-off-by: default avatarZhang Rui <rui.zhang@intel.com>
    02361418
cpu-cooling-api.txt 1.07 KB