[PATCH v2] Revert "drm/radeon: handle PCIe root ports with addressing limitations"

[Alex Deucher]

This causes screen corruption when using the GPU which makes the
system unusable.

It was noticed by several people closer to when the change went in as
well.  We looked into it a bit at the time but couldn't determine the
problem.  It only seems to affect really old chips (like 15-20 years
old) which makes it hard to reproduce if you don't have an old system.
There were a couple of threads at the time, but nothing was resolved.
I was able to find one of them:
https://lkml.org/lkml/2019/12/14/263

This reverts commit 33b3ad3788ab ("drm/radeon: handle PCIe root ports with addressing limitations").

Bug: https://bugzilla.kernel.org/show_bug.cgi?id=206973
Bug: https://bugzilla.kernel.org/show_bug.cgi?id=206697
Bug: https://bugzilla.kernel.org/show_bug.cgi?id=207763
Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/1140
Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/1287
Fixes: 33b3ad3788ab ("drm/radeon: handle PCIe root ports with addressing limitations")
Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
Cc: stable at vger.kernel.org
Cc: Christoph Hellwig <hch at lst.de>
Cc: christian.koenig at amd.com
---

v2: provide a better commit message.  The issue seems to be related to himem.
Any ideas?

 drivers/gpu/drm/radeon/radeon.h        |  1 +
 drivers/gpu/drm/radeon/radeon_device.c | 13 ++++++++-----
 drivers/gpu/drm/radeon/radeon_ttm.c    |  2 +-
 3 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/radeon/radeon.h b/drivers/gpu/drm/radeon/radeon.h
index cc4f58d16589..019f756b3f80 100644
--- a/drivers/gpu/drm/radeon/radeon.h
+++ b/drivers/gpu/drm/radeon/radeon.h
@@ -2391,6 +2391,7 @@ struct radeon_device {
 	struct radeon_wb		wb;
 	struct radeon_dummy_page	dummy_page;
 	bool				shutdown;
+	bool				need_dma32;
 	bool				need_swiotlb;
 	bool				accel_working;
 	bool				fastfb_working; /* IGP feature*/
diff --git a/drivers/gpu/drm/radeon/radeon_device.c b/drivers/gpu/drm/radeon/radeon_device.c
index 266e3cbbd09b..f74c74ad8b5d 100644
--- a/drivers/gpu/drm/radeon/radeon_device.c
+++ b/drivers/gpu/drm/radeon/radeon_device.c
@@ -1363,25 +1363,28 @@ int radeon_device_init(struct radeon_device *rdev,
 	else
 		rdev->mc.mc_mask = 0xffffffffULL; /* 32 bit MC */
 
-	/* set DMA mask.
+	/* set DMA mask + need_dma32 flags.
 	 * PCIE - can handle 40-bits.
 	 * IGP - can handle 40-bits
 	 * AGP - generally dma32 is safest
 	 * PCI - dma32 for legacy pci gart, 40 bits on newer asics
 	 */
-	dma_bits = 40;
+	rdev->need_dma32 = false;
 	if (rdev->flags & RADEON_IS_AGP)
-		dma_bits = 32;
+		rdev->need_dma32 = true;
 	if ((rdev->flags & RADEON_IS_PCI) &&
 	    (rdev->family <= CHIP_RS740))
-		dma_bits = 32;
+		rdev->need_dma32 = true;
 #ifdef CONFIG_PPC64
 	if (rdev->family == CHIP_CEDAR)
-		dma_bits = 32;
+		rdev->need_dma32 = true;
 #endif
 
+	dma_bits = rdev->need_dma32 ? 32 : 40;
 	r = dma_set_mask_and_coherent(&rdev->pdev->dev, DMA_BIT_MASK(dma_bits));
 	if (r) {
+		rdev->need_dma32 = true;
+		dma_bits = 32;
 		pr_warn("radeon: No suitable DMA available\n");
 		return r;
 	}
diff --git a/drivers/gpu/drm/radeon/radeon_ttm.c b/drivers/gpu/drm/radeon/radeon_ttm.c
index 74ad50c7491c..7e5c2fb8eab0 100644
--- a/drivers/gpu/drm/radeon/radeon_ttm.c
+++ b/drivers/gpu/drm/radeon/radeon_ttm.c
@@ -738,7 +738,7 @@ int radeon_ttm_init(struct radeon_device *rdev)
 			       &radeon_bo_driver,
 			       rdev->ddev->anon_inode->i_mapping,
 			       rdev->ddev->vma_offset_manager,
-			       dma_addressing_limited(&rdev->pdev->dev));
+			       rdev->need_dma32);
 	if (r) {
 		DRM_ERROR("failed initializing buffer object driver(%d).\n", r);
 		return r;
-- 
2.25.4