[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@xxxxxxx/
[2]  https://lore.kernel.org/lkml/20201116181356.804590-1-sudeep.holla@xxxxxxx/
[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