linux-kernel - Re: [PATCH] Re: More than 2Gb problem (dvb related) ?

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Date:	Sat, 28 Apr 2007 21:14:37 +0100
From:	Jon Burgess <jburgess777@...glemail.com>
To:	linux-dvb@...uxtv.org
Cc:	v4l-dvb-maintainer@...uxtv.org,
	Markus Rechberger <mrechberger@...il.com>,
	Gregoire Favre <Gregoire.Favre@...il.com>,
	linux-kernel@...r.kernel.org, Lee Revell <rlrevell@...-job.com>
Subject: Re: [PATCH] Re: More than 2Gb problem (dvb related) ?

On Sat, 2007-04-28 at 18:17 +0100, Jon Burgess wrote:
> On Fri, 2007-04-27 at 18:06 -0400, Lee Revell wrote:
> > On 4/27/07, Jon Burgess <jburgess777@...glemail.com> wrote:
> > > Interesting - I see similar symptoms after upgrading my PC:
> > > * old PC was AMD Athlon 64 3000 w/ 2GB of RAM which had no issues
> > > * new PC is a Intel Core 2 Duo w/ 4GB of RAM and fails in the way you
> > > describe.
> > 
> > Driver using an incorrect DMA mask?
> > 
> > Lee
> 
> It appears the problem is that the driver is using streamed PCI and
> needs to explicitly sync the data otherwise it breaks when the SWIOTLB
> is in use. A call to pci_unmap_sg() was missing too.
> 
> This patch is against the current v4l-dvb HG tree.
> 
> I've only tested the change with a budget-ci card.
> 
> 	Jon
> 
> Signed-off-by: Jon Burgess <jburgess777@...glemail.com>

While the above patch works, it seems the underlying causes is that
vmalloc_32() is providing memory above 4Gb on x86-64 which is not what
the driver expects. This same issue came up a few weeks ago with regards
to DRM on radeon http://lkml.org/lkml/2007/4/1/257

Andi Kleen included a patch to ensure vmalloc_32() returns memory <4Gb
in a patch which is currently in -mm
 http://kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.21-rc7/2.6.21-rc7-mm2/broken-out/x86_64-mm-vmalloc-32.patch

With this patch applied the current driver appears to work OK. 

Attached is a smaller patch against v4l-dvb which just adds the missing
pci_unmap_sg() call.

	Jon

Signed-off-by: Jon Burgess <jburgess777@...glemail.com>

View attachment "dvb-pci-unmap-sg.patch" of type "text/x-patch" (1167 bytes)