Patch "drm/radeon: insist on 32-bit DMA for Cedar on PPC64/PPC64LE" has been added to the 4.14-stable tree

This is a note to let you know that I've just added the patch titled

drm/radeon: insist on 32-bit DMA for Cedar on PPC64/PPC64LE

to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:

     drm-radeon-insist-on-32-bit-dma-for-cedar-on-ppc64-ppc64le.patch

and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Ben Crocker <[email protected]>
Date: Thu, 22 Feb 2018 17:52:19 -0500
Subject: drm/radeon: insist on 32-bit DMA for Cedar on PPC64/PPC64LE

From: Ben Crocker <[email protected]>

commit 2c83029cda55a5e7665c7c6326909427d6a01350 upstream.

In radeon_device_init, set the need_dma32 flag for Cedar chips (e.g. FirePro 2270). This fixes, or at least works around, a bug on PowerPC exposed by last year's commits

8e3f1b1d8255105f31556aacf8aeb6071b00d469 (Russell Currey)

and

253fd51e2f533552ae35a0c661705da6c4842c1b (Alistair Popple)

which enabled the 64-bit DMA iommu bypass.

This caused the device to freeze, in some cases unrecoverably, and is the subject of several bug reports internal to Red Hat.

---
 drivers/gpu/drm/radeon/radeon_device.c |    4 ++++
 1 file changed, 4 insertions(+)

@@ -1397,6 +1397,10 @@ int radeon_device_init(struct radeon_dev
 	if ((rdev->flags & RADEON_IS_PCI) &&
 	    (rdev->family <= CHIP_RS740))
 		rdev->need_dma32 = true;
+#ifdef CONFIG_PPC64
+	if (rdev->family == CHIP_CEDAR)
+		rdev->need_dma32 = true;
+#endif
 
 	dma_bits = rdev->need_dma32 ? 32 : 40;
 	r = pci_set_dma_mask(rdev->pdev, DMA_BIT_MASK(dma_bits));

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/drm-radeon-insist-on-32-bit-dma-for-cedar-on-ppc64-ppc64le.patch