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Date: Mon, 20 Jul 2015 15:43:57 +0100
From: Punit Agrawal <punit.agrawal@....com>
To: Chanwoo Choi <cw00.choi@...sung.com>
Cc: edubezval@...il.com, rui.zhang@...el.com, myungjoo.ham@...sung.com,
kyungmin.park@...sung.com, ulf.hansson@...aro.org,
khilman@...aro.org, robh+dt@...nel.org, pawel.moll@....com,
mark.rutland@....com, ijc+devicetree@...lion.org.uk,
inki.dae@...sung.com, l.majewski@...sung.com,
kgene.kim@...sung.com, linux-pm@...r.kernel.org,
linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [RFC PATCH 0/2] thermal: Add generic devfreq cooling device
Hi Chanwoo,
Chanwoo Choi <cw00.choi@...sung.com> writes:
> Hi Punit,
>
> On 07/17/2015 07:53 PM, Punit Agrawal wrote:
>> Hi Chanwoo,
>>
>> Chanwoo Choi <cw00.choi@...sung.com> writes:
>>
>>> This patchset introduce the generic devfreq cooling device for generic thermal
>>> framework. The devfreq devices are used ad cooling device to reduce the
>>> overheating temperature. This patch is based on drivers/thermal/cpu_cooling.c.
>>> The devfreq cooling device can change the ragne of the frequency table of
>>> devfreq device according to cooling level in device tree file.
>>>
>>
>> Have you had a look at the devfreq cooling patches from Javi[0][1]? How
>> is the current patchset different?
>
> I didn't see Javi's patchset before. Thanks for your information.
>
> I reviewed ths Javi's patchset. Both Javi's patchset and my patchset
> has same concept except for applying the power allocator thermal governor
> as you below comment.
>
> But, there are some difference.
>
> First,
> I don't add new devfreq API (devfreq_set_max() / devfreq_set_min()).
> The my patchset used existing update_devfreq() to update the
> maximum frequency of devfreq device.
>
Ok.
> Second,
> In my patchset, the devfreq cooling device will be operated
> as existing cpu cooling device. If sensor measure the overheating
> temperature, devfreq cooling device will limit the maximum frequency
> of devfreq device.
Javi's patchset behaves exactly as you describe here.
> As below example, the devicetree file includes
> the overheating temperature information of each trip-point.
> - Javi's patchset used the static power value calculated by
> devfreq_cooling_gen_power_table() instead of temperature.
>
You've got this wrong.
The power table is used to model device power consumption which allows
the device to be used with the power_allocator governor. Refer to the
power_allocator documentation[2] to understand how it is used.
This doesn't change the behaviour when used with other governors.
[2] https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/thermal/power_allocator.txt?id=refs/tags/v4.2-rc3
> Third,
> Javi's patchset used the same string of type when calling
> the thermal_of_cooling_device_register()
> - Javi's patchset used always the same "devfreq" string.
> - My patchset used the different "thermal-devfreq-%d" string
> according to each devfreq cooling device.
>
Except for this difference (which needs to be fixed), the current
patchset is a subset of the functionality proposed in [1].
With the merging of the power_allocator governor in v4.2, it makes sense
for the devfreq cooling device to also include support for it -
especially when the functionality is already under discussion on the
list.
As such, it would be great if you could provide feedback on that thread.
Thanks,
Punit
> In my patchset, devfreq cooling device uses the same method
> to determine the throttling situation as existing cpu cooling
> device. It is just my opinion.
>
>>
>> At first glance, it seems that you are not implementing the extensions
>> that allow devfreq cooling devices to be used with power_allocator
>> thermal governor that got merged in v4.2-rc1.
>>
>> Thanks,
>> Punit
>>
>> [0] http://article.gmane.org/gmane.linux.power-management.general/61936
>> [1] http://article.gmane.org/gmane.linux.power-management.general/62417
>
> Thanks,
> Chanwoo Choi
>
>>
>>
>>> To verify the devfreq cooling device driver, I testd it with following platform:
>>>
>>> For example,
>>> - The Mali GPU of Exynos5433 SoC uses the devfreq framework to support the DVFS
>>> feature and Exynos5433 contains the G3D (GPU) thermal sensor. Following example
>>> explain the correlation between mali dt node and thermal sensor/zone.
>>> : thermal sensor : G3D sensor of Samsung Exynos5433 [1][2]
>>> : devfreq cooling device : Mali GPU [3]
>>>
>>> According to the temperature of g3d thermal sensor inclued in Exynos5433,
>>> devfreq cooling device can change the maximum frequency of Mali GPU.
>>>
>>> 1. In Exynos5433-based board dts file, Mali GPU dt node uses the devfreq
>>> framework to suppot the DVFS feature. Following dt node includes the
>>> both 'cooling-cells' and 'operating-points' which means the supported
>>> frequency entries:
>>>
>>> mali: mali@...C0000 {
>>> compatible = "arm,mali-midgard";
>>> reg = <0x14AC0000 0x5000>;
>>> interrupts = <0 282 0>, <0 283 0>, <0 281 0>;
>>> interrupt-names = "JOB", "MMU", "GPU";
>>> clocks = <&cmu_g3d CLK_ACLK_G3D>;
>>> clock-names = "clk_mali";
>>> power-domains = <&pd_g3d>;
>>> status = "disabled";
>>>
>>> #cooling-cells = <2>;
>>>
>>> operating-points = <
>>> 700000 1150000
>>> 600000 1150000
>>> 550000 1125000
>>> 500000 1075000
>>> 420000 1025000
>>> 350000 1025000
>>> 266000 1000000
>>> 160000 1000000
>>> >;
>>> };
>>>
>>> 2. In exynos5433.dtsi, G3D thermal sensor measure the temperature of Mali GPU:
>>>
>>> tmu_g3d: tmu@...70000 {
>>> compatible = "samsung,exynos5433-tmu";
>>> reg = <0x10070000 0x200>;
>>> interrupts = <0 99 0>;
>>> clocks = <&cmu_peris CLK_PCLK_TMU1_APBIF>,
>>> <&cmu_peris CLK_SCLK_TMU1>;
>>> clock-names = "tmu_apbif", "tmu_sclk";
>>> #include "exynos5433-tmu-sensor-conf.dtsi"
>>> status = "disabled";
>>> };
>>>
>>> 3. In exynos5433-tmu.dtsi, thermal-zones includes both trip points and
>>> cooling-maps of g3d thermal sensor. Following cooling-maps show the match
>>> between each trip point and each cooling device (devfreq device of mali):
>>>
>>> thermal-zones {
>>> /* ...... */
>>> g3d_thermal: g3d-thermal {
>>> thermal-sensors = <&tmu_g3d>;
>>> polling-delay-passive = <0>;
>>> polling-delay = <0>;
>>> trips {
>>> g3d_alert_0: g3d-alert-0 {
>>> temperature = <30000>; /* millicelsius */
>>> hysteresis = <10000>; /* millicelsius */
>>> type = "active";
>>> };
>>> g3d_alert_1: g3d-alert-1 {
>>> temperature = <40000>; /* millicelsius */
>>> hysteresis = <10000>; /* millicelsius */
>>> type = "active";
>>> };
>>>
>>> /* ...... */
>>> };
>>>
>>> cooling-maps {
>>> map0 {
>>> /* Set maximum frequency as 550MHz */
>>> trip = <&g3d_alert_0>;
>>> cooling-device = <&mali 2 2>;
>>> };
>>> map1 {
>>> /* Set maximum frequency as 420MHz */
>>> trip = <&g3d_alert_1>;
>>> cooling-device = <&mali 4 4>;
>>> };
>>>
>>> /* ...... */
>>> };
>>> };
>>>
>>> ......
>>> };
>>>
>>> [1] https://git.kernel.org/cgit/linux/kernel/git/kgene/linux-samsung.git/commit/?h=v4.3-next/dt64-samsung&id=ac008f6b537703bb9a6fcc3882ca4af3331aa24f
>>> [2] https://git.kernel.org/cgit/linux/kernel/git/kgene/linux-samsung.git/commit/?h=v4.3-next/dt64-samsung&id=bcddc3a84e49ca1c646cf2081687a544a15f9218
>>> [3] malideveloper.arm.com/downloads/drivers/TX041/r5p0-06rel0/TX041-SW-99002-r5p0-06rel0.tgz
>>>
>>> Chanwoo Choi (2):
>>> PM: devfreq: Add the prototype of update_devfreq() to export
>>> thermal: devfreq_cooling: Add generic devfreq cooling device implementaion
>>>
>>> .../devicetree/bindings/thermal/thermal.txt | 8 +-
>>> drivers/devfreq/devfreq.c | 22 +-
>>> drivers/thermal/Kconfig | 11 +
>>> drivers/thermal/Makefile | 3 +
>>> drivers/thermal/devfreq-cooling.c | 309 +++++++++++++++++++++
>>> include/linux/devfreq-cooling.h | 80 ++++++
>>> include/linux/devfreq.h | 7 +
>>> 7 files changed, 425 insertions(+), 15 deletions(-)
>>> create mode 100644 drivers/thermal/devfreq-cooling.c
>>> create mode 100644 include/linux/devfreq-cooling.h
>>
>
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