Re: [PATCH V2] ARM: PMU: fix runtime PM enable

[Kevin Hilman <khilman@deeprootsystems.com>]

Jon Hunter <jon-hunter@ti.com> writes:

> Commit 7be2958 (ARM: PMU: Add runtime PM Support) updated the ARM PMU code to
> use runtime PM which was prototyped and validated on the OMAP devices. In this
> commit, there is no call pm_runtime_enable() and for OMAP devices
> pm_runtime_enable() is currently being called from the OMAP PMU code when the
> PMU device is created. However, there are two problems with this:
>
> 1. For any other ARM device wishing to use runtime PM for PMU they will need
>    to call pm_runtime_enable() for runtime PM to work.
> 2. When booting with device-tree and using device-tree to create the PMU
>    device, pm_runtime_enable() needs to be called from within the ARM PERF
>    driver as we are no longer calling any device specific code to create the
>    device. Hence, PMU does not work on OMAP devices that use the runtime PM
>    callbacks when using device-tree to create the PMU device.
>
> Therefore,  call pm_runtime_enable() directly from the ARM PMU driver when
> registering the device. For platforms that do not use runtime PM,
> pm_runtime_enable() does nothing and for platforms that do use runtime PM but
> may not require it specifically for PMU, this will just add a little overhead
> when initialising and uninitialising the PMU device.
>
> Tested with PERF on OMAP2420, OMAP3430 and OMAP4460.
>
> V2 changes:
> - Call pm_runtime_enable() unconditionally on registering the PMU device.
>
> Signed-off-by: Jon Hunter <jon-hunter@ti.com>

Acked-by: Kevin Hilman <khilman@ti.com>