drm/radeon/kms: set DMA mask properly on newer PCI asics

If a card wasn't PCIE, we always set the DMA mask to 32 bits.
This is only applies to the old rage128/r1xx gart block on
early radeon asics (~r1xx-r4xx).  Newer PCI and IGP cards
can handle 40 bits just fine.
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>
Cc: Chen Jie <chenj@lemote.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/radeon_device.c

@@ -750,14 +750,15 @@ int radeon_device_init(struct radeon_device *rdev,
 
 	/* set DMA mask + need_dma32 flags.
 	 * PCIE - can handle 40-bits.
-	 * IGP - can handle 40-bits (in theory)
+	 * IGP - can handle 40-bits
 	 * AGP - generally dma32 is safest
-	 * PCI - only dma32
+	 * PCI - dma32 for legacy pci gart, 40 bits on newer asics
 	 */
 	rdev->need_dma32 = false;
 	if (rdev->flags & RADEON_IS_AGP)
 		rdev->need_dma32 = true;
-	if (rdev->flags & RADEON_IS_PCI)
+	if ((rdev->flags & RADEON_IS_PCI) &&
+	    (rdev->family < CHIP_RS400))
 		rdev->need_dma32 = true;
 
 	dma_bits = rdev->need_dma32 ? 32 : 40;