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[130.180.211.218]) by smtp.googlemail.com with ESMTPSA id w14-20020adfec4e000000b003141e629cb6sm214343wrn.101.2023.08.03.09.20.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 03 Aug 2023 09:20:06 -0700 (PDT) Message-ID: Date: Thu, 3 Aug 2023 18:20:06 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.11.0 Subject: Re: [PATCH v3 1/8] thermal: core: Add mechanism for connecting trips with driver data Content-Language: en-US To: "Rafael J. Wysocki" Cc: "Rafael J. Wysocki" , Linux ACPI , LKML , Linux PM , Michal Wilczynski , Zhang Rui , Srinivas Pandruvada References: <13318886.uLZWGnKmhe@kreacher> <12254967.O9o76ZdvQC@kreacher> <4501957.LvFx2qVVIh@kreacher> <2d0315d4-35b4-84db-4dcb-c9528abad825@linaro.org> <5c93d78d-835e-c740-280b-9d76456aaeda@linaro.org> From: Daniel Lezcano In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On 03/08/2023 16:15, Rafael J. Wysocki wrote: > On Thu, Aug 3, 2023 at 3:06 PM Daniel Lezcano wrote: >> >> On 02/08/2023 18:48, Rafael J. Wysocki wrote: >> >> [ ... ] >> >>>> Let me check if I can do something on top of your series to move it in >>>> the ACPI driver. >>> >>> It doesn't need to be on top of my series, so if you have an idea, >>> please just let me know what it is. >>> >>> It can't be entirely in the ACPI driver AFAICS, though, because >>> trips[i] need to be modified on updates and they belong to the core. >>> Hence, the driver needs some help from the core to get to them. It >>> can be something like "this is my trip tag and please give me the >>> address of the trip matching it" or similar, but it is needed, because >>> the driver has to assume that the trip indices used by it initially >>> may change. >> >> May be I'm missing something but driver_ref does not seems to be used >> except when assigning it, no? > > It is used on the other side. That is, the value assigned to the trip > field in it is accessed via trip_ref in the driver. > > The idea is that the driver puts a pointer to its local struct > thermal_trip_ref into a struct thermal_trip and the core stores the > address of that struct thermal_trip in there, which allows the driver > to access the struct thermal_trip via its local struct > thermal_trip_ref going forward. > > Admittedly, this is somewhat convoluted. > > I have an alternative approach in the works, just for illustration > purposes if nothing else, but I have encountered a problem that I > would like to ask you about. > > Namely, zone disabling is not particularly useful for preventing the > zone from being used while the trips are updated, because it has side > effects. First, it triggers __thermal_zone_device_update() and a > netlink message every time the mode changes, which can be kind of > overcome. Right > But second, if the mode is "disabled", it does not actually > prevent things like __thermal_zone_get_trip() from running and the > zone lock is the only thing that can be used for that AFAICS. > > So by "disabling" a thermal zone, did you mean changing its mode to > "disabled" or something else? Yes, that is what I meant. May be the initial proposal by updating the thermal trips pointer can solve that [1] IMO we can assume the trip point changes are very rare (if any), so rebuilding a new trip array and update the thermal zone with the pointer may solve the situation. The routine does a copy of the trips array, so it can reorder it without impacting the array passed as a parameter. And it can take the lock. We just have to constraint the update function to invalidate arrays with a number of trip points different from the one initially passed when creating the thermal zone. Alternatively, we can be smarter in the ACPI driver and update the corresponding temperature+hysteresis trip point by using the thermal_zone_set_trip() function. [1] https://lore.kernel.org/all/20230525140135.3589917-5-daniel.lezcano@linaro.org/ -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog