[PATCH] firmware/psci: Add debugfs support to ease debugging

[Dmitry Baryshkov]

On Thu, 28 Jul 2022 at 12:08, Sudeep Holla <sudeep.holla at arm.com> wrote:
>
> On Wed, Jul 27, 2022 at 11:09:01PM +0300, Dmitry Baryshkov wrote:
> > To ease debugging of PSCI supported features, add debugfs file called
> > 'psci' describing PSCI and SMC CC versions
>
> These 2 are for sure in the boot log. Having them is debugfs accessible
> via file system add not much value as we would hit issues quite early in
> the boot for most of the things related to PSCI.

Yes, it was just to have all the information in a single place.

> > enabled features and options.
> >
>
> We have psci_checker.c which does some minimal testing of PSCI. I prefer
> to add things to that rather than a debugfs as it is run during boot. IMO
> it is usual useful to debug things that cause boot issue most of the time.
> I am not against this so I will leave it to the maintainers.

In my case I was not debugging the boot issues (which of course would
have required a different approach), but I was trying to understand
runtime capabilities, thus debugfs fits pretty well.

Another point for the debugfs entry: most of the people run the kernel
with the psci_checker being turned off, but with debugfs being
enabled. If we are trying to narrow down firmware capabilities of the
random device, it is much easier to ask them to cat the dbeugfs file
rather than to rebuild the kernel.

-- 
With best wishes
Dmitry