Hi Arnd,

On 8/26/15 01:48, Arnd Bergmann wrote:

On Wednesday 26 August 2015 00:33:25 Suravee Suthikulpanit wrote:

quoted

This patch adds support to setup DMA coherency for PCI device using
the ACPI _CCA attribute. According to the ACPI spec, the _CCA attribute
is required for ARM64. Therefore, this patch is a pre-req for ACPI PCI
support for ARM64 which is currently in development.

Also, this should not affect other architectures that does not define
CONFIG_ACPI_CCA_REQUIRED, since the default value is coherent.

We only support ACPI on SBSA compliant platforms, and SBSA mandates
cache-coherent PCI, so I don't think this is actually needed,
just use coherent all the time and do WARN_ON(!CCA) to catch people
that try to incorrectly use ACPI on a non-SBSA platform.

	Arnd

Thanks for pointing out. The CONFIG_ACPI_CCA_REQUIRED is already existed 
and selected in arch/arm64/Kconfig, and used for both PCI and non-PCI 
devices. I am not adding anything specific for the PCI case.

Although, I think WARN_ON(!CCA) when it is required is a good idea. I'll 
find a proper place for it.

Thanks,
Suravee.

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