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Message-ID: <b0677eff-e80c-48ba-a67b-edaaa037895f@linaro.org> Date: Mon, 1 Jul 2024 17:50:14 +0200 From: Daniel Lezcano <daniel.lezcano@...aro.org> To: "Rafael J. Wysocki" <rafael@...nel.org> Cc: linux-pm@...r.kernel.org, Zhang Rui <rui.zhang@...el.com>, Lukasz Luba <lukasz.luba@....com>, Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" <devicetree@...r.kernel.org>, open list <linux-kernel@...r.kernel.org> Subject: Re: [PATCH] thermal/core: Introduce user trip points On 01/07/2024 17:47, Rafael J. Wysocki wrote: > On Mon, Jul 1, 2024 at 5:13 PM Daniel Lezcano <daniel.lezcano@...aro.org> wrote: >> >> On 28/06/2024 15:56, Rafael J. Wysocki wrote: >>> On Thu, Jun 27, 2024 at 10:55 AM Daniel Lezcano >>> <daniel.lezcano@...aro.org> wrote: >>>> >>>> Currently the thermal framework has 4 trip point types: >>>> >>>> - active : basically for fans (or anything requiring energy to cool >>>> down) >>>> >>>> - passive : a performance limiter >>>> >>>> - hot : for a last action before reaching critical >>>> >>>> - critical : a without return threshold leading to a system shutdown >>>> >>>> A thermal zone monitors the temperature regarding these trip >>>> points. The old way to do that is actively polling the temperature >>>> which is very bad for embedded systems, especially mobile and it is >>>> even worse today as we can have more than fifty thermal zones. The >>>> modern way is to rely on the driver to send an interrupt when the trip >>>> points are crossed, so the system can sleep while the temperature >>>> monitoring is offloaded to a dedicated hardware. >>>> >>>> However, the thermal aspect is also managed from userspace to protect >>>> the user, especially tracking down the skin temperature sensor. The >>>> logic is more complex than what we found in the kernel because it >>>> needs multiple sources indicating the thermal situation of the entire >>>> system. >>>> >>>> For this reason it needs to setup trip points at different levels in >>>> order to get informed about what is going on with some thermal zones >>>> when running some specific application. >>>> >>>> For instance, the skin temperature must be limited to 43°C on a long >>>> run but can go to 48°C for 10 minutes, or 60°C for 1 minute. >>>> >>>> The thermal engine must then rely on trip points to monitor those >>>> temperatures. Unfortunately, today there is only 'active' and >>>> 'passive' trip points which has a specific meaning for the kernel, not >>>> the userspace. That leads to hacks in different platforms for mobile >>>> and embedded systems where 'active' trip points are used to send >>>> notification to the userspace. This is obviously not right because >>>> these trip are handled by the kernel. >>>> >>>> This patch introduces the 'user' trip point type where its semantic is >>>> simple: do nothing at the kernel level, just send a notification to >>>> the user space. >>>> >>>> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org> >>>> --- >>>> .../devicetree/bindings/thermal/thermal-zones.yaml | 1 + >>>> drivers/thermal/thermal_core.c | 8 ++++++++ >>>> drivers/thermal/thermal_of.c | 1 + >>>> drivers/thermal/thermal_trace.h | 4 +++- >>>> drivers/thermal/thermal_trip.c | 1 + >>>> include/uapi/linux/thermal.h | 1 + >>>> 6 files changed, 15 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/Documentation/devicetree/bindings/thermal/thermal-zones.yaml b/Documentation/devicetree/bindings/thermal/thermal-zones.yaml >>>> index 68398e7e8655..cb9ea54a192e 100644 >>>> --- a/Documentation/devicetree/bindings/thermal/thermal-zones.yaml >>>> +++ b/Documentation/devicetree/bindings/thermal/thermal-zones.yaml >>>> @@ -153,6 +153,7 @@ patternProperties: >>>> type: >>>> $ref: /schemas/types.yaml#/definitions/string >>>> enum: >>>> + - user # enable user notification >>>> - active # enable active cooling e.g. fans >>>> - passive # enable passive cooling e.g. throttling cpu >>>> - hot # send notification to driver >>>> diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c >>>> index 2aa04c46a425..506f880d9aa9 100644 >>>> --- a/drivers/thermal/thermal_core.c >>>> +++ b/drivers/thermal/thermal_core.c >>>> @@ -734,6 +734,14 @@ int thermal_bind_cdev_to_trip(struct thermal_zone_device *tz, >>>> if (tz != pos1 || cdev != pos2) >>>> return -EINVAL; >>>> >>>> + /* >>>> + * It is not allowed to bind a cooling device with a trip >>>> + * point user type because no mitigation should happen from >>>> + * the kernel with these trip points >>>> + */ >>>> + if (trip->type == THERMAL_TRIP_USER) >>>> + return -EINVAL; >>> >>> Maybe print a debug message when bailing out here? >> >> After thinking a bit about the message, it sounds to me that is a really >> an error in the firmware if we end up binding an 'user' trip point. >> >> What about the following message: >> >> dev_err(tz->device, "Trying to bind the cooling device '%s' with an >> 'user' trip point id=%d", cdev->type, trip->id); > > s/an// I think. > > Also I wouldn't use dev_err() as it indicates a kernel issue. Maybe > dev_info(tz->device, FW_BUG ...)? Right, thanks -- <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | <http://twitter.com/#!/linaroorg> Twitter | <http://www.linaro.org/linaro-blog/> Blog
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