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

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Message-ID: <20110603231350.GA20316@dumpdata.com>
Date:	Fri, 3 Jun 2011 19:13:50 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Alex Deucher <alexdeucher@...il.com>
Cc:	Daniel Haid <d.haid@...i.tv>, linux-kernel@...r.kernel.org,
	Andi Kleen <andi@...stfloor.org>, airlied@...ux.ie
Subject: Re: [PATCH] tentative fix for radeon on systems >4GB without
 hardware iommu

On Fri, Jun 03, 2011 at 04:44:59PM -0400, Alex Deucher wrote:
> 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

<nods>

Daniel, did you find other graphic drivers that forget to set need_dma32
after failing to set the dma_mask ?

> 
> 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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