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Message-ID: <f78d50e2-cda5-48a6-b591-96218bd83e2b@linaro.org> Date: Mon, 1 Jul 2024 15:17:03 +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 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? > > A check for "user" trips would need to be added to > thermal_governor_trip_crossed() and to the .manage() callbacks in the > power allocator, step-wise and fair-share governors, if I'm not > mistaken. Especially fair-share and power allocator should not take > them into account IMV. I'm not sure the power_allocator needs to change anything. The trip point used is switch_on which is only derived from passive or active trip point, so it is not possible to have a user trip point used in the manage callback. Did I miss something ? -- <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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