Am Dienstag, 7. August 2018, 14:31:49 CEST schrieb Marc Zyngier:

On 07/08/18 13:09, Heiko Stuebner wrote:

quoted

Hi Marc,

Am Dienstag, 7. August 2018, 10:54:05 CEST schrieb Marc Zyngier:

quoted

pm_runtime_get_if_in_use can fail: either PM has been disabled
altogether (-EINVAL), or the device hasn't been enabled yet (0).
Sadly, the Rockchip IOMMU driver tends to conflate the two things
by considering a non-zero return value as successful.

This has the consequence of hiding other bugs, so let's handle this
case throughout the driver, with a WARN_ON_ONCE so that we can try
and work out what happened.

Fixes: 0f181d3cf7d98 ("iommu/rockchip: Add runtime PM support")
Signed-off-by: Marc Zyngier <redacted>

I'm still not sure about the !CONFIG_PM case, as it was probably silently
working in that case before

Do we agree that this is an orthogonal problem though?

Nope ;-) .... I.e. right now the code ignores the -EINVAL from disabled PM
and continues, possibly even handling the irq correctly.

If it actually worked is a different matter, as I guess nobody really tried
with !PM in the past.

Now with error-handling we always return IRQ_NONE for !PM.

quoted

But on the other hand we're also already running over it in other places
like in the iommu-shutdown and I guess if someone _really_ disabled
CONFIG_PM, a lot of additional stuff would fail anyway.

So should we wrap that in some #ifdef magic, just ignore it or simply
select PM similar to what Tegra, Renesas and Vexpress seem to do?

I guess I like the 3rd option best ;-)

It probably doesn't hurt. At what level do you want it? As a dependency
to the IOMMU? or to the platform?

I guess it might be best to go the Tegra, etc way. Whoever in their right
mind would want to drive a mobile platform without any form for power
management ;-) .

I can do these patches for arm32+arm64 myself ... I just wanted to put
that thought out there - in case that was just a stupid idea of mine :-D .


Heiko