Re: [PATCH] iommu: Do not probe devices on IOMMU-less busses

[Joerg Roedel <joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>]

On Mon, May 11, 2020 at 06:10:00PM +0200, Thierry Reding wrote:
> From: Thierry Reding <treding-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
> 
> The host1x bus implemented on Tegra SoCs is primarily an abstraction to
> create logical device from multiple platform devices. Since the devices
> in such a setup are typically hierarchical, DMA setup still needs to be
> done so that DMA masks can be properly inherited, but we don't actually
> want to attach the host1x logical devices to any IOMMU. The platform
> devices that make up the logical device are responsible for memory bus
> transactions, so it is them that will need to be attached to the IOMMU.
> 
> Add a check to __iommu_probe_device() that aborts IOMMU setup early for
> busses that don't have the IOMMU operations pointer set since they will
> cause a crash otherwise.
> 
> Signed-off-by: Thierry Reding <treding-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
> ---
> Note that this is probably also required for the BCMA bus implemented in
> drivers/bcma/main.c since no IOMMU operations are ever assigned to that
> either.
> 
>  drivers/iommu/iommu.c | 3 +++
>  1 file changed, 3 insertions(+)

Applied, thanks.