Various MediaTek SoCs use GPU integration silicon named "MFlexGraphics"
by MediaTek. On the MT8196 and MT6991 SoCs, interacting with this
integration silicon is required to power on the GPU.

This glue silicon is in the form of an embedded microcontroller running
special-purpose firmware, which autonomously adjusts clocks and
regulators.

Implement a driver, modelled as a pmdomain driver with a
set_performance_state operation, to support these SoCs.

The driver also exposes the actual achieved clock rate, as read back
from the MCU, as common clock framework clocks, by acting as a clock
provider as well.

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

The use of R7 in the SMCCC conflicts with the compiler's use of R7 as a frame
pointer in Thumb2 mode, which is forcibly enabled by Clang when profiling
hooks are inserted via the -pg switch.

This is a known issue and similar driver workaround this with a Makefile
ifdef. Exact workaround are applied in
drivers/firmware/arm_scmi/transports/Makefile and other similar driver.

Suggested-by: Sudeep Holla <sudeep.holla@arm.com>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202501201840.XmpHXpQ4-lkp@intel.com/
Fixes: 82e703dd438b ("pmdomain: airoha: Add Airoha CPU PM Domain support")
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Link: https://lore.kernel.org/r/20250120153817.11807-1-ansuelsmth@gmail.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

Add Airoha CPU PM Domain support to control frequency and power of CPU
present on Airoha EN7581 SoC.

Frequency and power can be controlled with the use of the SMC command by
passing the performance state. The driver also expose a read-only clock
that expose the current CPU frequency with SMC command.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Link: https://lore.kernel.org/r/20250109131313.32317-1-ansuelsmth@gmail.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

It has been pointed out that naming a subsystem "genpd" isn't very
self-explanatory and the acronym itself that means Generic PM Domain, is
known only by a limited group of people.

In a way to improve the situation, let's rename the subsystem to pmdomain,
which ideally should indicate that this is about so called Power Domains or
"PM domains" as we often also use within the Linux Kernel terminology.

Suggested-by: Rafael J. Wysocki <rafael@kernel.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Rafael J. Wysocki <rafael@kernel.org>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20230912221127.487327-1-ulf.hansson@linaro.org