On 14.06.2017 10:39, Erik Faye-Lund wrote:
On Wed, Jun 14, 2017 at 1:15 AM, Dmitry Osipenko digetx@gmail.com wrote:
There is no IOMMU on Tegra20, instead a GART would be picked as an IOMMU provider.
Signed-off-by: Dmitry Osipenko digetx@gmail.com Acked-by: Joerg Roedel jroedel@suse.de
drivers/gpu/drm/tegra/drm.c | 3 ++- drivers/gpu/host1x/dev.c | 3 ++- 2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/tegra/drm.c b/drivers/gpu/drm/tegra/drm.c index e999391aedc9..aa7988dcc28f 100644 --- a/drivers/gpu/drm/tegra/drm.c +++ b/drivers/gpu/drm/tegra/drm.c @@ -131,7 +131,8 @@ static int tegra_drm_load(struct drm_device *drm, unsigned long flags) if (!tegra) return -ENOMEM;
if (iommu_present(&platform_bus_type)) {
if (iommu_present(&platform_bus_type) &&
!of_machine_is_compatible("nvidia,tegra20")) { u64 carveout_start, carveout_end, gem_start, gem_end; struct iommu_domain_geometry *geometry; unsigned long order;
diff --git a/drivers/gpu/host1x/dev.c b/drivers/gpu/host1x/dev.c index f05ebb14fa63..6a805ed908c3 100644 --- a/drivers/gpu/host1x/dev.c +++ b/drivers/gpu/host1x/dev.c @@ -177,7 +177,8 @@ static int host1x_probe(struct platform_device *pdev) return err; }
if (iommu_present(&platform_bus_type)) {
if (iommu_present(&platform_bus_type) &&
!of_machine_is_compatible("nvidia,tegra20")) { struct iommu_domain_geometry *geometry; unsigned long order;
This doesn't feel great... The commit message says there's no IOMMU, but iommu_present says otherwise. I know there's some more subtleties here, and the commit message does hint at this. But...
If we don't want to treat the GART as an IOMMU, shouldn't we somehow make sure iommu_present() doesn't return true in these cases (or perhaps make something like tegra_use_iommu(), with a comment explaining why we don't want to allow the GART to be treated like a proper IOMMU)? These seems to be the only Tegra-specific calls to iommu_present()...
That being said, the patch seems to have the right effect...
We don't want to treat the GART as an IOMMU right now, but I'd want to change that in the (near?) future, so it's a kinda trivial preparation patch that restores the GART driver and these of_machine_is_compatible() are supposed to go away later. Probably I should mention this in the commit message(?).
I think we can add a Tegra20 specific IOCTL for an allocation of GART-able memory and use it for a stuff like opentegra's EXA, its fallback allocations migration is a pita and reserved CMA is never enough =)