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Subject: Re: [PATCH 00/11] thermal: add new flag irq-mode for trip point
To:     =?UTF-8?Q?Krzysztof_Koz=c5=82owski?= <k.kozlowski.k+lkml@gmail.com>
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From:   Lukasz Luba <l.luba@partner.samsung.com>
Date:   Wed, 17 Oct 2018 09:42:41 +0200
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Hi Krzysztof,

On 10/17/2018 09:03 AM, Krzysztof Kozłowski wrote:
> On Tue, 16 Oct 2018 at 16:56, Lukasz Luba <l.luba@partner.samsung.com> wrote:
>>
>> Hi all,
>>
>> This patch set adds new flag and mechanism in thermal trip point in DT.
>> The current situation with 'passive' (passive cooling - DVFS)
>> trip point is that it enables polling mode in thermal framework.
> 
> For DT platform, I checked it some months ago... and that time I was
> pretty sure - passive mode does not enable polling (unless you tell it
> explicitly with "polling-delay-passive"). Maybe something changed...
> but quick look at the code tell me that not. Passive does not indicate
> polling mode.
> 
> Why do you think that passive enables polling?
Please check dt file which implements 2 more trip points that HW
supports:
arch/arm/boot/dts/exynos5422-odroidxu3-common.dtsi

In that file we have this trick with 'active' present.
Yes, you are right, 'polling-delay-passive' enables it in
the thermal code (for whole thermal zone).
Unfortunately, if you change the bellow 'active' to 'passive'
in that file, they will start polling, which is not what we want.
--------8<-------------------------
         thermal-zones {
                 cpu0_thermal: cpu0-thermal {
                         thermal-sensors = <&tmu_cpu0 0>;
                         polling-delay-passive = <250>;
                         polling-delay = <0>;
                         trips {
                                 cpu0_alert0: cpu-alert-0 {
                                         temperature = <50000>; /* 
millicelsius */
                                         hysteresis = <5000>; /* 
millicelsius */
                                         type = "active";
                                 };
                                 cpu0_alert1: cpu-alert-1 {
                                         temperature = <60000>; /* 
millicelsius */
                                         hysteresis = <5000>; /* 
millicelsius */
                                         type = "active";
                                 };
                                 cpu0_alert2: cpu-alert-2 {
                                         temperature = <70000>; /* 
millicelsius */
                                         hysteresis = <5000>; /* 
millicelsius */
                                         type = "active";
                                 };
                                 cpu0_crit0: cpu-crit-0 {
                                         temperature = <120000>; /* 
millicelsius */
                                         hysteresis = <0>; /* 
millicelsius */
                                         type = "critical";
                                 };
                                 /*
                                  * Exynos542x supports only 4 trip-points
                                  * so for these polling mode is required.
                                  * Start polling at temperature level 
of last
                                  * interrupt-driven trip: cpu0_alert2
                                  */
                                 cpu0_alert3: cpu-alert-3 {
                                         temperature = <70000>; /* 
millicelsius */
                                         hysteresis = <10000>; /* 
millicelsius */
                                         type = "passive";
                                 };
                                 cpu0_alert4: cpu-alert-4 {
                                         temperature = <85000>; /* 
millicelsius */
                                         hysteresis = <10000>; /* 
millicelsius */
                                         type = "passive";
                                 };
                         };
---------------->8-----------------------------

If you have some other ideas how to handle this case,
I am happy to discuss.

Regards,
Lukasz
> 
> Best regards
> 
> 
>> If the device supports irqs fired when the desired temerature is met,
>> thermal framwork should be notifed from driver's irq routine.
>> This is sufficent and there is no need of polling.
>> As a workaround, people declare trip point as 'active'
>> (active cooling, i.e. fan) to bypass polling mode setup in thermal
>> framework.
>>
>> With this patch set trip point 'passive' declared in DT with explicit flag:
>> 'irq-mode;' will not register itself as polling mode.
>>
>> A good example is Exynos4 SoC family, where there is 4 HW supported
>> trip points and there is a need of 6. The rest 2 are declared as 'passive'
>> without 'irq-mode;' flag, thus polling needed.
>>
>> It does not break existing design for trip points which do not have 'irq-mode'
>> flag - they will use polling.
>>
>> For consistency this flag should be added to all trip point types('active',
>> 'passive', 'hot', 'critical') when need (meaning, when irq will notify thermal
>> framework).
>>
>> Regards,
>> Lukasz Luba
>>
>> Lukasz Luba (11):
>>    thermal: remove unused function parameter
>>    thermal: add irq-mode configuration for trip point
>>    thermal: add new sysfs file for irq-mode
>>    Doc: thermal: new irq-mode for trip point
>>    Doc: DT: thermal: new irq-mode for trip point
>>    DT: arm64: exynos: add support for thermal trip irq-mode
>>    DT: arm64: exynos7: add support for thermal trip irq-mode
>>    DT: arm: exynos4: add support for thermal trip irq-mode
>>    DT: arm: exynos: add support for thermal trip irq-mode
>>    DT: arm: exynos: add support for thermal trip irq-mode
>>    DT: arm: exynos: add support for thermal trip irq-mode
>>
>>   .../devicetree/bindings/thermal/thermal.txt        |   7 ++
>>   Documentation/thermal/sysfs-api.txt                |   9 ++
>>   arch/arm/boot/dts/exynos4-cpu-thermal.dtsi         |  10 +-
>>   arch/arm/boot/dts/exynos5410-odroidxu.dts          |  10 +-
>>   arch/arm/boot/dts/exynos5420-trip-points.dtsi      |  10 +-
>>   arch/arm/boot/dts/exynos5422-odroidxu3-common.dtsi |  40 +++++---
>>   arch/arm64/boot/dts/exynos/exynos5433-tmu.dtsi     | 105 ++++++++++++++-------
>>   .../arm64/boot/dts/exynos/exynos7-trip-points.dtsi |   8 ++
>>   drivers/thermal/of-thermal.c                       |  17 ++++
>>   drivers/thermal/thermal_core.c                     |  16 ++--
>>   drivers/thermal/thermal_sysfs.c                    |  53 ++++++++++-
>>   include/linux/thermal.h                            |   5 +
>>   12 files changed, 226 insertions(+), 64 deletions(-)
>>
>> --
>> 2.7.4
>>
> 
>