RFC Add support for PDC timer for wake-ups

RPMH based targets require that the next wake-up timer value needs to be programmed to PDC (Power Domain Controller) which has its own timer and is in an always on power domain. PDC wakes-up the RSC and sets up the resources back in active state before the processor is woken up by a timer interrupt. In order to query next timer wake-up, the patch-set depends on patch - Export next wakeup time of a CPU[1].

The kernel does not notify that the CPU powering down is the last CPU. So in this version, next wake-up is programmed to PDC each time when a CPU goes to power collapse. The current approach can be revisited in future if OS-initiated support becomes available that enables certain actions to be taken when last core enters deepest low power mode.

Please review these patches. Your inputs would be greatly appreciated.

Thanks,
Raju.

Dependencies:
[1].https://lore.kernel.org/patchwork/patch/1019432/

Raju P.L.S.S.S.N (5):
drivers: qcom: rpmh-rsc: Add regmap for RSC controller
drivers: qcom: rpmh-pdc-timer: add PDC timer support for RPMH based
SoCs
dt-bindings: Add PDC timer bindings for Qualcomm SoCs
drivers: qcom: rpmh-pdc-timer: Add power management ops
arm64: dts: msm: add PDC timer for apps_rsc for SDM845

 .../devicetree/bindings/soc/qcom/rpmh-rsc.txt |  29 +++
 arch/arm64/boot/dts/qcom/sdm845.dtsi          |   9 +
 drivers/soc/qcom/Kconfig                      |   9 +
 drivers/soc/qcom/Makefile                     |   1 +
 drivers/soc/qcom/rpmh-pdc-timer.c             | 205 ++++++++++++++++++
 drivers/soc/qcom/rpmh-rsc.c                   |  14 ++
 6 files changed, 267 insertions(+)
 create mode 100644 drivers/soc/qcom/rpmh-pdc-timer.c

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