[PATCH v2 4/4] iommu: Get DT/ACPI parsing into the proper probe path

[Geert Uytterhoeven]

Hi Robin,

On Tue, 18 Mar 2025 at 18:24, Robin Murphy <robin.murphy at arm.com> wrote:
> On 18/03/2025 4:37 pm, Geert Uytterhoeven wrote:
> [...]
> > Thanks for your patch, which is now commit bcb81ac6ae3c2ef9 ("iommu:
> > Get DT/ACPI parsing into the proper probe path") in iommu/next.
> >
> > This patch triggers two issues on R-Car Gen3 platforms:
> >
> > 1. I am seeing a warning on Renesas Salvator-XS with R-Car M3N
> > (but not on the similar board with R-Car H3), and only for SATA[1].
> > Unfortunately commit 73d2f10957f517e5 ("iommu: Don't warn prematurely
> > about dodgy probes") does not help:
> [...]
> >      Call trace:
> >       __iommu_probe_device+0x208/0x38c (P)
> >       iommu_probe_device+0x34/0x74
> >       of_iommu_configure+0x128/0x200
> >       of_dma_configure_id+0xdc/0x1d4
> >       platform_dma_configure+0x48/0x6c
> >       really_probe+0xf0/0x260
> >       __driver_probe_device+0xec/0x104
> >       driver_probe_device+0x3c/0xc0
>
> Hurrah, this is the warning doing the correct job - something *is* off
> if we're now getting here without the IOMMU configuration being done
> already (for a normal device with no other funny business going on).
>
> > 2. The IOMMU driver's iommu_ops.of_xlate() callback is called about
> > three times as much as before:
>
> That would suggest that the fwspec gets set up OK, then something later
> in the __iommu_probe_device() path fails and tears it down again, so the
> next attempt starts from scratch. Do you see the "Cannot attach to
> IPMMU" message firing?

I do not see such messages.

> And similarly to the Rockchip case, does the
> below help?

The below is basically the same as your "[PATCH] iommu/ipmmu-vmsa:
Register in a sensible order"[1].  While that fixes my first issue,
it does not fix the second (harmless?) issue.

Note that I only noticed the second issue because I have local debug
code in soc_device_match().  Perhaps it happens, unnoticed, on other
systems too?

Thanks!

[1] https://lore.kernel.org/53be6667544de65a15415b699e38a9a965692e45.1742481687.git.robin.murphy@arm.com/

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds