Re: [PATCH] drm/tegra: Stop using iommu_present()

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 2022-04-06 15:32, Dmitry Osipenko wrote:
On 4/5/22 17:19, Robin Murphy wrote:
Remove the pointless check. host1x_drm_wants_iommu() cannot return true
unless an IOMMU exists for the host1x platform device, which at the moment
means the iommu_present() test could never fail.

Signed-off-by: Robin Murphy <robin.murphy@xxxxxxx>
---
  drivers/gpu/drm/tegra/drm.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/tegra/drm.c b/drivers/gpu/drm/tegra/drm.c
index 9464f522e257..bc4321561400 100644
--- a/drivers/gpu/drm/tegra/drm.c
+++ b/drivers/gpu/drm/tegra/drm.c
@@ -1149,7 +1149,7 @@ static int host1x_drm_probe(struct host1x_device *dev)
  		goto put;
  	}
- if (host1x_drm_wants_iommu(dev) && iommu_present(&platform_bus_type)) {
+	if (host1x_drm_wants_iommu(dev)) {
  		tegra->domain = iommu_domain_alloc(&platform_bus_type);
  		if (!tegra->domain) {
  			err = -ENOMEM;

host1x_drm_wants_iommu() returns true if there is no IOMMU for the
host1x platform device of Tegra20/30 SoCs.

Ah, apparently this is another example of what happens when I write patches late on a Friday night...

So on second look, what we want to ascertain here is whether dev has an IOMMU, but only if the host1x parent is not addressing-limited, either because it can also use the IOMMU, or because all possible addresses are small enough anyway, right? Are we specifically looking for the host1x having a DMA-API-managed domain, or can that also end up using the tegra->domain or another unmanaged domain too? I can't quite figure out from the comments whether it's physical addresses, IOVAs, or both that we're concerned with here.

Thanks,
Robin.



[Index of Archives]     [ARM Kernel]     [Linux ARM]     [Linux ARM MSM]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]

  Powered by Linux