Re: using DMA-API on ARM

[Catalin Marinas <catalin.marinas@arm.com>]

On Mon, Dec 08, 2014 at 12:55:38PM +0000, Johannes Stezenbach wrote:
> On Fri, Dec 05, 2014 at 06:53:03PM +0000, Catalin Marinas wrote:
> > On Fri, Dec 05, 2014 at 06:39:45PM +0000, Catalin Marinas wrote:
> > > 
> > > Does your system have an L2 cache? What's the SoC topology, can PCIe see
> > > such L2 cache (or snoop the L1 caches)?
> > 
> > BTW, if you really have a PL310-like L2 cache, have a look at some
> > patches (I've seen similar symptoms) and make sure your configuration is
> > correct:
> > 
> > http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=6395/1
> > 
> > http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=6529/1
> > 
> > The first one is vexpress specific. The second one was eventually
> > discarded by Russell (I don't remember the reason, I guess it's because
> > SoC code is supposed to set the right bits in there anyway). In your
> > case, such bits may be set up by firmware, so Linux cannot fix anything
> > up.
> 
> How do you avoid the unpredictable behavior mentioned in the
> PL310 TRM when the Shared Attribute Invalidate Enable bit is set?
> http://infocenter.arm.com/help/topic/com.arm.doc.ddi0246h/Ceggcfcj.html

So you talk about "Shared Attribute _Invalidate_ Enable" (bit 13) while
I talk about "Shared Attribute _Override_ Enable" (bit 22).

In addition, Shared _Invalidate_ behaviour can only be enabled if Shared
Attribute _Override_ Enable bit is not set.

-- 
Catalin