linux-kernel - Re: [PATCH] tentative fix for radeon on systems >4GB without hardware iommu

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Date:	Fri, 3 Jun 2011 16:44:59 -0400
From:	Alex Deucher <alexdeucher@...il.com>
To:	Daniel Haid <d.haid@...i.tv>
Cc:	linux-kernel@...r.kernel.org, Andi Kleen <andi@...stfloor.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	airlied@...ux.ie
Subject: Re: [PATCH] tentative fix for radeon on systems >4GB without hardware iommu

On Fri, Jun 3, 2011 at 1:31 PM, Daniel Haid <d.haid@...i.tv> wrote:
> 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

This looks like the correct fix. rdev->need_dma32 is used when we init
ttm for memory management later.

Alex

Acked-by: Alex Deucher <alexdeucher@...il.com>

>
> --- linux-2.6.39-gentoo/drivers/gpu/drm/radeon/radeon_device.c.old
>  2011-06-03 19:11:33.208891994 +0200
> +++ linux-2.6.39-gentoo/drivers/gpu/drm/radeon/radeon_device.c  2011-06-03
> 19:21:10.240337986 +0200
> @@ -752,6 +752,7 @@ int radeon_device_init(struct radeon_dev
>        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");
>        }
>
>
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