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

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Message-ID: <CAMuHMdXt9gQxBSVrWw1VSji+faxga4Vo_NRie27K=EtdUMMa_Q@mail.gmail.com>
Date: Tue, 25 Mar 2025 16:32:42 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Robin Murphy <robin.murphy@....com>
Cc: Lorenzo Pieralisi <lpieralisi@...nel.org>, Hanjun Guo <guohanjun@...wei.com>, 
	Sudeep Holla <sudeep.holla@....com>, "Rafael J. Wysocki" <rafael@...nel.org>, Len Brown <lenb@...nel.org>, 
	Russell King <linux@...linux.org.uk>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Danilo Krummrich <dakr@...nel.org>, Stuart Yoder <stuyoder@...il.com>, 
	Laurentiu Tudor <laurentiu.tudor@....com>, Nipun Gupta <nipun.gupta@....com>, 
	Nikhil Agarwal <nikhil.agarwal@....com>, Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>, 
	Rob Herring <robh@...nel.org>, Saravana Kannan <saravanak@...gle.com>, 
	Bjorn Helgaas <bhelgaas@...gle.com>, linux-acpi@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	iommu@...ts.linux.dev, devicetree@...r.kernel.org, linux-pci@...r.kernel.org, 
	Charan Teja Kalla <quic_charante@...cinc.com>, 
	Linux-Renesas <linux-renesas-soc@...r.kernel.org>
Subject: Re: [PATCH v2 4/4] iommu: Get DT/ACPI parsing into the proper probe path

Hi Robin,

On Tue, 18 Mar 2025 at 18:24, Robin Murphy <robin.murphy@....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@...ux-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