drm/msm: Revert "drm/msm: Stop using iommu_present()"

This reverts commit e2a88ea. The commit
in question makes msm_use_mmu() check whether the DRM 'component master'
device is translated by the IOMMU. At this moment it is the 'mdss'
device.
However on platforms using the MDP5 driver (e.g. MSM8916/APQ8016,
MSM8996/APQ8096) it's the mdp5 device, which has the iommus property
(and thus is "translated by the IOMMU"). This results in these devices
being broken with the following lines in the dmesg.

[drm] Initialized msm 1.9.0 20130625 for 1a00000.mdss on minor 0
msm 1a00000.mdss: [drm:adreno_request_fw] loaded qcom/a300_pm4.fw from new location
msm 1a00000.mdss: [drm:adreno_request_fw] loaded qcom/a300_pfp.fw from new location
msm 1a00000.mdss: [drm:get_pages] *ERROR* could not get pages: -28
msm 1a00000.mdss: could not allocate stolen bo
msm 1a00000.mdss: [drm:get_pages] *ERROR* could not get pages: -28
msm 1a00000.mdss: [drm:msm_alloc_stolen_fb] *ERROR* failed to allocate buffer object
msm 1a00000.mdss: [drm:msm_fbdev_create] *ERROR* failed to allocate fb

Getting the mdp5 device pointer from this function is not that easy at
this moment. Thus this patch is reverted till the MDSS rework [1] lands.
It will make the mdp5/dpu1 device component master and the check will be
legit.

[1] https://patchwork.freedesktop.org/series/98525/

Fixes: e2a88ea ("drm/msm: Stop using iommu_present()")
Signed-off-by: Dmitry Baryshkov <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Rob Clark <[email protected]>

drivers/gpu/drm/msm/msm_drv.c

@@ -274,7 +274,7 @@ bool msm_use_mmu(struct drm_device *dev)
 	struct msm_drm_private *priv = dev->dev_private;
 
 	/* a2xx comes with its own MMU */
-	return priv->is_a2xx || device_iommu_mapped(dev->dev);
+	return priv->is_a2xx || iommu_present(&platform_bus_type);
 }
 
 static int msm_init_vram(struct drm_device *dev)