[v6,0/5] add meson secure watchdog driver

The watchdog controller on the Meson-A/C series SoCs is moved to secure world,
We have to call SMC instruction to trap the ATF for watchdog operation. These
operations are different from previous SoCs, so we introduce a new watchdog
driver to support this kind of SoCs.

Changes since v5 at [4]:
- take the wdt node as child node of secure-monitor
- update dt-binding description
- invoke of_platform_default_populate() instantiate wdt device according to Rob's suggestion at [5]
- find the secure-monitor node through the wdt parent node instead of of_find_compatible_node()
- add Guenter's Reviewed-by

Changes since v4 at [3]:
- add watchdog node in dts, and introduce a new optional property "timeout-sec"
- add dt-binding for meson secure watchdog
- instantiate wdt device through dts node instead of platform_device_register_simple()

Changes since v3 at [2]:
- add SM_A1_ prefix for WATCHDOG_OPS
- remove phandle to secure-monitor node
- remove watchdog node from dts, and register wdt device by platform_device_register_simple()
- remove dt-binding for meson secure watchdog
- use the msec as unit of timeout parameter which is passed to fw side

Changes since v2 at [1]:
- remove useless dependency in Kconfig
- return zero when getting left time value fails

Changes since v1 at [0]:
- add a new dependency in Kconfig
- simplify/add the return operation
- remove useless ping operation when setting the timeout
- fix some return values
- fix the license statement

[0]:https://lore.kernel.org/linux-amlogic/1570874721-36077-1-git-send-email-xingyu.chen@amlogic.com
[1]:https://lore.kernel.org/linux-amlogic/1571387622-35132-1-git-send-email-xingyu.chen@amlogic.com
[2]:https://lore.kernel.org/linux-amlogic/1571983984-11771-1-git-send-email-xingyu.chen@amlogic.com
[3]:https://lore.kernel.org/linux-amlogic/1574685218-31164-1-git-send-email-xingyu.chen@amlogic.com
[4]:https://lore.kernel.org/linux-amlogic/1576153187-28378-1-git-send-email-xingyu.chen@amlogic.com
[5]:https://patchwork.kernel.org/patch/11288017

Xingyu Chen (5):
  firmware: meson_sm: add new SMC ID support for accessing secure
    watchdog
  firmware: meson_sm: populate platform device based on the child node
  dt-bindings: watchdog: add new binding for meson secure watchdog
  watchdog: add meson secure watchdog driver
  arm64: dts: a1: add secure watchdog controller

 .../bindings/watchdog/amlogic,meson-sec-wdt.yaml   |  40 +++++
 arch/arm64/boot/dts/amlogic/meson-a1.dtsi          |   6 +
 drivers/firmware/meson/meson_sm.c                  |   3 +
 drivers/watchdog/Kconfig                           |  16 ++
 drivers/watchdog/Makefile                          |   1 +
 drivers/watchdog/meson_sec_wdt.c                   | 185 +++++++++++++++++++++
 include/linux/firmware/meson/meson_sm.h            |   1 +
 7 files changed, 252 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/watchdog/amlogic,meson-sec-wdt.yaml
 create mode 100644 drivers/watchdog/meson_sec_wdt.c