Re: [PATCH v7 00/17] Introduce ACPI for ARM64 based on ACPI 5.1

[Arnd Bergmann]

On Friday 16 January 2015 14:55:45 Will Deacon wrote:
> Hi Tom,
> 
> On Fri, Jan 16, 2015 at 02:45:30PM +0000, Tom Lendacky wrote:
> > I have tested ACPI-enablement patches for the amd-xgbe/amd-xgbe-phy
> > drivers that I'm about to submit upstream with the V7 patch series
> > on the AMD Seattle server platform. There does not appear to be support
> > for the _CCA attribute in this patch series. The amd-xgbe driver will
> > setup the device domain and cache attributes based on the presence of
> > this attribute, but it requires the arch support to assign the proper
> > DMA operations in order for it to all work correctly.
> > 
> > Overriding the _CCA attribute in the driver, I was able to successfully
> > test the driver and this patch series.
> 
> Hopefully this will all be addressed when the IORT parts of ACPI have
> settled down (the current proposal allows for these attributes to be
> described as well as their interaction with things like IOMMUs).
> 
> In the meantime, are you falling back to non-coherent DMA? If so, what
> attributes have you settled on? We need to be really careful not to
> corrupt data during cache invalidatation when mapping a non-coherent
> buffer for the CPU.

I think in case of ACPI we should use cache-coherent as the default,
as this is what all servers will use for DMA masters.

	Arnd
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