From mboxrd@z Thu Jan  1 00:00:00 1970
From: arnd@arndb.de (Arnd Bergmann)
Date: Fri, 16 Jan 2015 16:14:13 +0100
Subject: [PATCH v7 00/17] Introduce ACPI for ARM64 based on ACPI 5.1
In-Reply-To: <20150116145545.GR7091@arm.com>
References: <1421247905-3749-1-git-send-email-hanjun.guo@linaro.org>
 <54B9240A.7060003@amd.com> <20150116145545.GR7091@arm.com>
Message-ID: <2198633.UpIyI82Yon@wuerfel>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

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