Re: [PATCH v4 05/16] iommu: Move bus setup to IOMMU device registration

[Jon Hunter]

On 06/10/2022 16:27, Robin Murphy wrote:
> On 2022-10-06 15:01, Jon Hunter wrote:
> > Hi Robin,
> >
> > On 15/08/2022 17:20, Robin Murphy wrote:
> > > Move the bus setup to iommu_device_register(). This should allow
> > > bus_iommu_probe() to be correctly replayed for multiple IOMMU instances,
> > > and leaves bus_set_iommu() as a glorified no-op to be cleaned up next.
> > >
> > > At this point we can also handle cleanup better than just rolling back
> > > the most-recently-touched bus upon failure - which may release devices
> > > owned by other already-registered instances, and still leave devices on
> > > other buses with dangling pointers to the failed instance. Now it's easy
> > > to clean up the exact footprint of a given instance, no more, no less.
> >
> >
> > Since this change, I have noticed that the DRM driver on Tegra20 is 
> > failing to probe and I am seeing ...
> >
> >   tegra-gr2d 54140000.gr2d: failed to attach to domain: -19
> >   drm drm: failed to initialize 54140000.gr2d: -19
> >
> > Bisect points to this change and reverting it fixes it. Let me know if 
> > you have any thoughts.
>
> Oh, apparently what's happened is that I've inadvertently enabled the 
> tegra-gart driver, since it seems that *wasn't* calling bus_set_iommu() 
> before. Looking at the history, it appears to have been that way since 
> c7e3ca515e78 ("iommu/tegra: gart: Do not register with bus"), so 
> essentially that driver has been broken and useless for close to 8 years 
> now :(
>
> Given that, I'd be inclined to "fix" it as below, or just give up and 
> delete the whole thing.
>
> Thanks,
> Robin.
>
> ----->8-----
> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> index 5c5cb5bee8b6..7b3f7fd6e527 100644
> --- a/drivers/iommu/Kconfig
> +++ b/drivers/iommu/Kconfig
> @@ -230,6 +230,7 @@ config TEGRA_IOMMU_GART
>       bool "Tegra GART IOMMU Support"
>       depends on ARCH_TEGRA_2x_SOC
>       depends on TEGRA_MC
> +    depends on BROKEN
>       select IOMMU_API
>       help
>         Enables support for remapping discontiguous physical memory


Thanks Robin. This works for me.

Thierry, Dmitry, we need a fix for v6.1 and so OK with the above?

Jon

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nvpublic