Re: [PATCH v2 2/2] clk: qcom: gdsc: add RPM_ALWAYS_ON flag

[Konrad Dybcio]

On 6/6/26 2:34 PM, Herman van Hazendonk wrote:
> Some power domains need to stay powered across runtime PM even though
> their clocks may still gate, and only collapse on full system suspend.
> Add an RPM_ALWAYS_ON flag that maps to the existing
> GENPD_FLAG_RPM_ALWAYS_ON on the underlying generic_pm_domain.
> 
> This is distinct from the existing ALWAYS_ON flag (which keeps the
> domain permanently enabled and prevents collapse even during system
> suspend) and from leaving the flag unset (which allows the domain to
> collapse on every runtime-idle transition).
> 
> GENPD_FLAG_RPM_ALWAYS_ON, like GENPD_FLAG_ALWAYS_ON, requires the
> underlying genpd to be in the ON state at pm_genpd_init() time --
> the framework rejects registration otherwise. Fold RPM_ALWAYS_ON
> into the gdsc_init() block that already force-enables ALWAYS_ON
> GDSCs found powered down at sync time so the flag combination is
> honoured consistently.
> 
> The first user is the upcoming MSM8x60 MMCC driver, which needs
> RPM_ALWAYS_ON on the a2xx (Adreno 220) GFX3D footswitch: cold-cycling
> the GPU rail on every runtime idle forces an a2xx_hw_init microcode
> reload whose MMIO burst can stall the shared MMSS AXI fabric when it
> coincides with an MDP display client-switch underrun, hard-hanging
> the SoC. Letting the rail stay up during runtime PM (clocks still
> gate, idle power is still saved) and only collapsing on system
> suspend avoids the corner case while still allowing full power-down
> during deep sleep.

Is this something that downstream works around, or is that observed
behavior with upstream?

Konrad