Re: [PATCH] spi: cadence: Correct initialisation of runtime PM again

[Charles Keepax <ckeepax@xxxxxxxxxxxxxxxxxxxxx>]

On Fri, Jul 16, 2021 at 08:21:33PM +0200, Marek Vasut wrote:
> The original implementation of RPM handling in probe() was mostly
> correct, except it failed to call pm_runtime_get_*() to activate the
> hardware. The subsequent fix, 734882a8bf98 ("spi: cadence: Correct
> initialisation of runtime PM"), breaks the implementation further,
> to the point where the system using this hard IP on ZynqMP hangs on
> boot, because it accesses hardware which is gated off.
> 
> Undo 734882a8bf98 ("spi: cadence: Correct initialisation of runtime
> PM") and instead add missing pm_runtime_get_noresume() and move the
> RPM disabling all the way to the end of probe(). That makes ZynqMP
> not hang on boot yet again.
> 
> Fixes: 734882a8bf98 ("spi: cadence: Correct initialisation of runtime PM")
> Signed-off-by: Marek Vasut <marex@xxxxxxx>
> Cc: Charles Keepax <ckeepax@xxxxxxxxxxxxxxxxxxxxx>
> Cc: Mark Brown <broonie@xxxxxxxxxx>
> ---

For my own edification do you know exactly what the problem was
on your system here? I am assuming my mistake was that without the
pm_runtime reference being taken, some required parent doesn't get
enabled, which is convienently fine on my Zynq but not your ZynqMP?

The inclusion of the IRQ stuff in the pm_runtime block makes me a
little nervous as if the problem is that your hardware generates
a spurious IRQ on boot and that is where the bad access comes from
this code feels racy. The original code did the put before the IRQ
registers as well.

All that said, works on my Zynq:

Tested-by: Charles Keepax <ckeepax@xxxxxxxxxxxxxxxxxxxxx>

Thanks,
Charles