[PATCH v12] cpufreq: mediatek-hw: Add support for Mediatek cpufreq HW driver

[Hector Yuan]

The CPUfreq HW present in some Mediatek chipsets offloads the steps necessary for changing the frequency of CPUs. 
The driver implements the cpufreq driver interface for this hardware engine. 

From v11 to v12, there are two modifications.
1. Based on patchset[1], align binding with scmi for performance domain(latest version).
2. Shrink binding example wording. 

From v8 to v9, there are three more modifications.
1. Based on patchset[2], align binding with scmi for performance domain.
2. Add the CPUFREQ fast switch function support and define DVFS latency.
3. Based on patchser[3], add energy model API parameter for mW.

From v7 to v8, there are three more patches based on patchset v8[4].
This patchset is about to register power table to Energy model for EAS and thermal usage.
1. EM CPU power table
- Register energy model table for EAS and thermal cooling device usage.
- Read the coresponding LUT for power table.
2. SVS initialization
- The SVS(Smart Voltage Scaling) engine is a hardware which is
  used to calculate optimized voltage values for CPU power domain.
  DVFS driver could apply those optimized voltage values to reduce power consumption.
- Driver will polling if HW engine is done for SVS initialization.
  After that, driver will read power table and register it to EAS.
- CPUs must be in power on state when doing SVS. Use pm_qos to block cpu-idle state for SVS initializing.
3. Cooling device flag
- Add cooling device flag for thermal
[1]  https://lore.kernel.org/linux-devicetree/20210517155458.1016707-1-sudeep.holla@arm.com/
[2]  https://lore.kernel.org/lkml/20201116181356.804590-1-sudeep.holla@arm.com/
[3]  https://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git/commit/?h=linux-next&id=c250d50fe2ce627ca9805d9c8ac11cbbf922a4a6
[4]  https://lkml.org/lkml/2020/9/23/384


Hector.Yuan (2):
  cpufreq: mediatek-hw: Add support for CPUFREQ HW
  dt-bindings: cpufreq: add bindings for MediaTek cpufreq HW

 .../bindings/cpufreq/cpufreq-mediatek-hw.yaml      |   71 ++++
 drivers/cpufreq/Kconfig.arm                        |   12 +
 drivers/cpufreq/Makefile                           |    1 +
 drivers/cpufreq/mediatek-cpufreq-hw.c              |  370 ++++++++++++++++++++
 4 files changed, 454 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/cpufreq/cpufreq-mediatek-hw.yaml
 create mode 100644 drivers/cpufreq/mediatek-cpufreq-hw.c