On Tue, Feb 05, 2019 at 11:29:12PM +0100, Thierry Reding wrote: > > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/gpu/host1x/cdma.c#n106 > > > > Yes, I think we I can come up with a nicer helper for that. > > One thing I could also try is to remove direct IOMMU API usage at least > from the host1x driver. I think this might work nowadays. > > For Tegra DRM we still need direct IOMMU API usage because we need to be > able to map into an IOMMU domain without knowing the struct device * > that we're mapping for (it could be needed by any of up to four display > controllers). For host1x we always only have one struct device *, so the > DMA mapping API should be good enough.
If you can convert it to plain DMA API usage, please do. I did look into an IOMMU API memory allocator, and while we can do it easily for coherent devices, we need some arch hooks for non-coherent device support. With a pending series from me we have those for arm64, but 32-bit arm support will require a lot more work first.
