[PATCH v6] Mediatek SCPSYS power domain support

[Sascha Hauer]

Just a small update to this series with a memory corruption bug fixed.

This series adds support for the MediaTek SCPSYS unit.

The SCPSYS unit handles several power management related tasks such
as thermal measurement, DVFS, interrupt filter and low level sleep
control.

The initial support only contains the generic power domain handling.
This is needed to turn on power to the different power domains.

The driver is quite straight forward now. Due to the lack of a better
place I have put it to drivers/soc/mediatek. As the SCPSYS unit has
several other tasks that also do not fit into some specific subsystem
this probably is a good place for this driver.

Please review, any input welcome.

Sascha

changes since v5:
- Fix array out of bounds access
- Fix typo

Changes since v4:
- move Kconfig dependency "select PM_GENERIC_DOMAINS if PM" from arch/arm64
  next to the driver which needs this dependency
- drop unnecessary clk[] array from struct scp and make the array local to
  the function which needs it.
- Disable clock when enabling the domain fails
- Drop error message when devm_clk_get fails. The core already issues a
  similar warning
- Add clocks/clock-names description to the binding doc

Changes since v3:
- Drop unnecessary MODULE_* macros for builtin code
- introduce scpsys_domain_is_on() function instead of open coding this
  twice
- Drop unnecessary initialisation of power_o[ff|n]_latencies. The kernel
  updates them with the measured values anyway.

changes since v2:
- Add missing include/linux/soc/mediatek/infracfg.h file
- rename VDE -> VDEC, VEN -> VENC, DIS -> DISP and VEN2 -> VENC_LT
  to make the abbreviatons more clear
- make of_device_id const
- remove double loop
- fix hunk in wrong patch
- Fix order of domains. Some domains depend on other domains. Reorder
  the domains so that all domains can be turned on in order when
  CONFIG_PM is disabled. Also fixes earlier mixups in the domain array
- Do not allow compilation as modules. pm_domains cannot be removed, so
  compilation as module is not that useful
- reorder Kconfig items alphabetically
- reorder #includes alphabetically
- select MTK_INFRACFG instead of depending on it
- Use only two clocks as dependencies for the domains. The previously
  used 5 clocks are not necessary as confirmed by the hardware designers
- use 'genpd' as variable name for struct generic_pm_domain like done in
  other pm code

changes since v1:
- make MFG_ASYNC a subdomain of MFG_2D and MFG_2D a subdomain of MFG
- Add (now hopefully properly) infracfg register handling again
- Add clock handling
- Fix on/off mixup in error message
- Make readonly data const
- Fix MODULE_LICENSE to GPL v2

changes since RFC:

- add a commit log to driver patch
- drop manipulating infracfg registers for now, can be added (properly)
  later
- Add warning messages when errors occur
- add NULL pointer check for kmalloc