linux-kernel - [34-longterm 054/179] drm/radeon/kms: fix for radeon on systems >4GB without hardware iommu

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Date:	Mon, 14 May 2012 22:12:30 -0400
From:	Paul Gortmaker <paul.gortmaker@...driver.com>
To:	<stable@...nel.org>, <linux-kernel@...r.kernel.org>
Subject: [34-longterm 054/179] drm/radeon/kms: fix for radeon on systems >4GB without hardware iommu

From: Daniel Haid <d.haid@...i.tv>

                   -------------------
    This is a commit scheduled for the next v2.6.34 longterm release.
    http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git
    If you see a problem with using this for longterm, please comment.
                   -------------------

commit 62fff811d73095bd95579d72f558f03c78f7914a upstream.

On my x86_64 system with >4GB of ram and swiotlb instead of
a hardware iommu (because I have a VIA chipset), the call
to pci_set_dma_mask (see below) with 40bits returns an error.

But it seems that the radeon driver is designed to have
need_dma32 = true exactly if pci_set_dma_mask is called
with 32 bits and false if it is called with 40 bits.

I have read somewhere that the default are 32 bits. So if the
call fails I suppose that need_dma32 should be set to true.

And indeed the patch fixes the problem I have had before
and which I had described here:
http://choon.net/forum/read.php?21,106131,115940

Acked-by: Alex Deucher <alexdeucher@...il.com>
cc: stable@...nel.org
Signed-off-by: Dave Airlie <airlied@...hat.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com>
---
 drivers/gpu/drm/radeon/radeon_device.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/radeon/radeon_device.c b/drivers/gpu/drm/radeon/radeon_device.c
index 2008481..feff1c8 100644
--- a/drivers/gpu/drm/radeon/radeon_device.c
+++ b/drivers/gpu/drm/radeon/radeon_device.c
@@ -641,6 +641,7 @@ int radeon_device_init(struct radeon_device *rdev,
 	dma_bits = rdev->need_dma32 ? 32 : 40;
 	r = pci_set_dma_mask(rdev->pdev, DMA_BIT_MASK(dma_bits));
 	if (r) {
+		rdev->need_dma32 = true;
 		printk(KERN_WARNING "radeon: No suitable DMA available.\n");
 	}
 
-- 
1.7.9.6

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