thermal: core: Allow thermal zones to tell the core to ignore them
The iwlwifi wireless driver registers a thermal zone that is only needed when the network interface handled by it is up and it wants that thermal zone to be effectively ignored by the core otherwise. Before commit a8a26177 ("thermal: core: Call monitor_thermal_zone() if zone temperature is invalid") that could be achieved by returning an error code from the thermal zone's .get_temp() callback because the core did not really handle errors returned by it almost at all. However, commit a8a26177 made the core attempt to recover from the situation in which the temperature of a thermal zone cannot be determined due to errors returned by its .get_temp() and is always invalid from the core's perspective. That was done because there are thermal zones in which .get_temp() returns errors to start with due to some difficulties related to the initialization ordering, but then it will start to produce valid temperature values at one point. Unfortunately, the simple approach taken by commit a8a26177, which is to poll the thermal zone periodically until its .get_temp() callback starts to return valid temperature values, is at odds with the special thermal zone in iwlwifi in which .get_temp() may always return an error because its network interface may always be down. If that happens, every attempt to invoke the thermal zone's .get_temp() callback resulting in an error causes the thermal core to print a dev_warn() message to the kernel log which is super-noisy. To address this problem, make the core handle the case in which .get_temp() returns 0, but the temperature value returned by it is not actually valid, in a special way. Namely, make the core completely ignore the invalid temperature value coming from .get_temp() in that case, which requires folding in update_temperature() into its caller and a few related changes. On the iwlwifi side, modify iwl_mvm_tzone_get_temp() to return 0 and put THERMAL_TEMP_INVALID into the temperature return memory location instead of returning an error when the firmware is not running or it is not of the right type. Also, to clearly separate the handling of invalid temperature values from the thermal zone initialization, introduce a special THERMAL_TEMP_INIT value specifically for the latter purpose. Fixes: a8a26177 ("thermal: core: Call monitor_thermal_zone() if zone temperature is invalid") Closes: https://lore.kernel.org/linux-pm/20240715044527.GA1544@sol.localdomain/Reported-by:Eric Biggers <ebiggers@kernel.org> Reported-by:
Stefan Lippers-Hollmann <s.l-h@gmx.de> Link: https://bugzilla.kernel.org/show_bug.cgi?id=201761Tested-by:
Oleksandr Natalenko <oleksandr@natalenko.name> Tested-by:
Rafael J. Wysocki <rafael.j.wysocki@intel.com> Link: https://patch.msgid.link/4950004.31r3eYUQgx@rjwysocki.net [ rjw: Rebased on top of the current mainline ] Signed-off-by:
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