thermal: cpu_cooling: Migrate to using the EM framework

The newly introduced Energy Model framework manages power cost tables in
a generic way. Moreover, it supports several types of models since the
tables can come from DT or firmware (through SCMI) for example. On the
other hand, the cpu_cooling subsystem manages its own power cost tables
using only DT data.

In order to avoid the duplication of data in the kernel, and in order to
enable IPA with EMs coming from more than just DT, remove the private
tables from cpu_cooling.c and migrate it to using the centralized EM
framework. Doing so should have no visible functional impact for
existing users of IPA since:

 - recent extenstions to the the PM_OPP infrastructure enable the
   registration of EMs in PM_EM using the DT property used by IPA;

 - the existing upstream cpufreq drivers marked with the
   'CPUFREQ_IS_COOLING_DEV' flag all use the aforementioned PM_OPP
   infrastructure, which means they all support PM_EM. The only two
   exceptions are qoriq-cpufreq which doesn't in fact use an EM and
   scmi-cpufreq which doesn't use DT for power costs.

For existing users of cpu_cooling, PM_EM tables will contain the exact
same power values that IPA used to compute on its own until now. The
only new dependency for them is to compile in CONFIG_ENERGY_MODEL.

The case where the thermal subsystem is used without an Energy Model
(cpufreq_cooling_ops) is handled by looking directly at CPUFreq's
frequency table which is already a dependency for cpu_cooling.c anyway.
Since the thermal framework expects the cooling states in a particular
order, bail out whenever the CPUFreq table is unsorted, since that is
fairly uncommon in general, and there are currently no users of
cpu_cooling for this use-case.

Acked-by: Daniel Lezcano <[email protected]>
Acked-by: Viresh Kumar <[email protected]>
Signed-off-by: Quentin Perret <[email protected]>
Signed-off-by: Daniel Lezcano <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: Quentin Perret

drivers/thermal/Kconfig

@@ -144,6 +144,7 @@ config THERMAL_GOV_USER_SPACE
 
 config THERMAL_GOV_POWER_ALLOCATOR
 	bool "Power allocator thermal governor"
+	depends on ENERGY_MODEL
 	help
 	  Enable this to manage platform thermals by dynamically
 	  allocating and limiting power to devices.