On Tue, Jul 2, 2024 at 1:03 PM Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote: > > On Tue, Jul 2, 2024 at 12:56 PM Daniel Lezcano > <daniel.lezcano@xxxxxxxxxx> wrote: > > > > On 02/07/2024 12:22, Rafael J. Wysocki wrote: > > > On Tue, Jul 2, 2024 at 11:29 AM Daniel Lezcano > > > <daniel.lezcano@xxxxxxxxxx> wrote: > > >> > > >> On 01/07/2024 18:26, Rob Herring wrote: > > >>> On Thu, Jun 27, 2024 at 10:54:50AM +0200, Daniel Lezcano 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. > > >>> > > >>> Sounds like OS behavior/policy though I guess the existing ones kind are > > >>> too. Maybe we should have defined *what* action to take and then the OS > > >>> could decide whether what actions to handle vs. pass it up a level. > > >> > > >> Right > > >> > > >>> Why can't userspace just ask to be notified at a trip point it > > >>> defines? > > >> > > >> Yes I think it is possible to create a netlink message to create a trip > > >> point which will return a trip id. > > >> > > >> Rafael what do you think ? > > > > > > Trips cannot be created on the fly ATM. > > > > > > What can be done is to create trips that are invalid to start with and > > > then set their temperature via sysfs. This has been done already for > > > quite a while AFAICS. > > > > Yes, I remember that. > > > > I would like to avoid introducing more weirdness in the thermal > > framework which deserve a clear ABI. > > > > What is missing to create new trip points on the fly ? > > A different data structure to store them (essentially, a list instead > of an array). > > I doubt it's worth the hassle. > > What's wrong with the current approach mentioned above? It will need > to be supported going forward anyway. BTW, there are two different concepts that seem to be mixed here. One of them is a "trigger" that will cause a netlink message to be sent to user space when a given temperature level is crossed (either way) and nothing more. This in principle can be added to any thermal zone (even tripless) and should be possible to implement as a separate mechanism independent of trip points. The other one is a pair of trip points that can be set "around" the current zone temperature so that the .set_trips() callback uses them to program interrupts to trigger when one of them is crossed. This at least requires the thermal zone to provide a .set_trips() callback, so it depends on the driver registering the thermal zone. Arguably, the driver in question can reserve a pair of "trip slots" in the trip table passed to the zone registration function.
