[PATCH v3 0/2] Add fallback method to handle RPM notification in MPM driver

[Sneh Mankad]

MPM irqchip needs to notify RPM (Resource Power Manager) processor to read
the latest wake up capable interrupts when the CPU cluster is entering the
deepest idle state. This is done by sending IPC interrupt to RPM and is
implemented as .power_off() callback by registering MPM as parent power
domain to CPU cluster.

Such implementation earlier introduced a hard probe dependency between MPM
irqchip and CPU cluster power domains. That is MPM irqchip needs to finish
probe before PSCI power domains are probed.

The above problem has since been resolved after bd7f488a8e5d ("cpuidle:
psci: Fix support for probe deferral by dropping the faux device") / [1].
However, it makes sense to remodel the RPM notification in MPM irqchip due
to general consistency.

MPM is not really a power domain provider, all it needs is a notification
when CPU cluster is going to power collapse to carry out the RPM
notification. We can register for CPU_PM notifications for that purpose.
This way we can avoid such unrelated dependencies.

We cannot register MPM under CPU cluster power domain and rely on
GENPD notifications here, since that way cluster low power modes will be
blocked whenever some consumer of MPM, and in turn MPM itself, are
runtime active. This will add another unnecessary dependency for CPU
cluster low power modes.

For now as first step, register with cpu_pm as a fallback to manage RPM
notification. Trigger the RPM notification when the last CPU in CPU cluster
goes to power collapse.

Add idle states for CPUs and CPU cluster for Shikra.

[1] https://lore.kernel.org/all/20260909134240.685115374@xxxxxxxxxxxxxxxxxxx

Signed-off-by: Sneh Mankad <sneh.mankad@xxxxxxxxxxxxxxxx>
---
Changes in v3:
- Skip timer programming for now till we add support to register MPM
  under CPU cluster power domain without blocking its idle states.
- Skip modifying DTs other than Shikra to prioritize Shikra LPM
  enablement.
- Move genPD/cpu_pm registration after mbox_request_channel().
- Link to v2: https://lore.kernel.org/r/20261015-b4-shikra_lpm_addition-v2-0-ac7f1a0d5638@xxxxxxxxxxxxxxxx

Changes in v2:
- Enable Shikra LPMs in the first patch, following patches concern
  MPM driver.
- Register with cpu_pm as a fallback to manage RPM notification.
- Move USECS_TO_CYCLES and xloops_to_cycles to common header delay.h.
- Reformat qcom_mpm_offset() as per feedback.
- Avoid deleting cluster_pd node in qrb2210-rb1.dts.
- Link to v1: https://lore.kernel.org/r/20260713-b4-shikra_lpm_addition-v1-0-3d858df2cbbf@xxxxxxxxxxxxxxxx

---
Sneh Mankad (2):
      irqchip: irq-qcom-mpm: Register MPM with cpu_pm for RPM notification
      arm64: dts: qcom: shikra: Add CPU idle states

 arch/arm64/boot/dts/qcom/shikra.dtsi |  93 ++++++++++++++++++++++++++++++-
 drivers/irqchip/irq-qcom-mpm.c       | 104 ++++++++++++++++++++++++++---------
 2 files changed, 170 insertions(+), 27 deletions(-)
---
base-commit: 7777cc195ca1301a28008ca5cdb98bdb2a9d0def
change-id: 20260617-b4-shikra_lpm_addition-4a9bc82bafee

Best regards,
-- 
Sneh Mankad <sneh.mankad@xxxxxxxxxxxxxxxx>