iommu/tegra-smmu: Fix mc errors on tegra124-nyan

iommu/tegra-smmu: Fix mc errors on tegra124-nyan

Commit 25938c73cd79 ("iommu/tegra-smmu: Rework tegra_smmu_probe_device()")
removed certain hack in the tegra_smmu_probe() by relying on IOMMU core to
of_xlate SMMU's SID per device, so as to get rid of tegra_smmu_find() and
tegra_smmu_configure() that are typically done in the IOMMU core also.

This approach works for both existing devices that have DT nodes and other
devices (like PCI device) that don't exist in DT, on Tegra210 and Tegra3
upon testing. However, Page Fault errors are reported on tegra124-Nyan:

  tegra-mc 70019000.memory-controller: display0a: read @0xfe056b40:
	 EMEM address decode error (SMMU translation error [--S])
  tegra-mc 70019000.memory-controller: display0a: read @0xfe056b40:
	 Page fault (SMMU translation error [--S])

After debugging, I found that the mentioned commit changed some function
callback sequence of tegra-smmu's, resulting in enabling SMMU for display
client before display driver gets initialized. I couldn't reproduce exact
same issue on Tegra210 as Tegra124 (arm-32) differs at arch-level code.

Actually this Page Fault is a known issue, as on most of Tegra platforms,
display gets enabled by the bootloader for the splash screen feature, so
it keeps filling the framebuffer memory. A proper fix to this issue is to
1:1 linear map the framebuffer memory to IOVA space so the SMMU will have
the same address as the physical address in its page table. Yet, Thierry
has been working on the solution above for a year, and it hasn't merged.

Therefore, let's partially revert the mentioned commit to fix the errors.

The reason why we do a partial revert here is that we can still set priv
in ->of_xlate() callback for PCI devices. Meanwhile, devices existing in
DT, like display, will go through tegra_smmu_configure() at the stage of
bus_set_iommu() when SMMU gets probed(), as what it did before we merged
the mentioned commit.

Once we have the linear map solution for framebuffer memory, this change
can be cleaned away.

[Big thank to Guillaume who reported and helped debugging/verification]

Fixes: 25938c73cd79 ("iommu/tegra-smmu: Rework tegra_smmu_probe_device()")
Reported-by: Guillaume Tucker <guillaume.tucker@collabora.com>
Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>
Tested-by: Guillaume Tucker <guillaume.tucker@collabora.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20210218220702.1962-1-nicoleotsuka@gmail.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>