Re: [PATCH v6 3/3] firmware: QCOM_SCM: Allow qcom_scm driver to be loadable as a permenent module

John Stultz
2020-11-16T19:49:20Z

On Mon, Nov 16, 2020 at 8:36 AM Will Deacon <will@kernel.org> wrote:
> On Mon, Nov 16, 2020 at 04:59:36PM +0100, Thierry Reding wrote:
> > On Fri, Nov 06, 2020 at 04:27:10AM +0000, John Stultz wrote:
> > Unfortunately, the ARM SMMU module will eventually end up being loaded
> > once the root filesystem has been mounted (for example via SDHCI or
> > Ethernet, both with using just plain, non-IOMMU-backed DMA API) and then
> > initialize, configuring as "fault by default", which then results from a
> > slew of SMMU faults from all the devices that have previously configured
> > themselves without IOMMU support.
>
> I wonder if fw_devlink=on would help here?
>
> But either way, I'd be more inclined to revert this change if it's causing
> problems for !QCOM devices.
>
> Linus -- please can you drop this one (patch 3/3) for now, given that it's
> causing problems?

Agreed. Apologies again for the trouble.

I do feel like the probe timeout to handle optional links is causing a
lot of the trouble here. I expect fw_devlink would solve this, but it
may be awhile before it can be always enabled. I may see about
pushing the default probe timeout value to be a little further out
than init (I backed away from my last attempt as I didn't want to
cause long (30 second) delays for cases like NFS root, but maybe 2-5
seconds would be enough to make things work better for everyone).

thanks
-john