Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: [PATCH 2/2] ACPI / scan: Parse _CCA and setup device coherency | Date | Wed, 29 Apr 2015 16:03:19 +0200 |
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On Wednesday 29 April 2015 08:44:09 Suravee Suthikulpanit wrote: > + device->flags.cca_seen = 1; > + } else if (IS_ENABLED(CONFIG_ACPI_MUST_HAVE_CCA)) { > + /* > + * Architecture has specified that if the device > + * can do DMA, it must have ACPI _CCA object. > + * Here, there could be two cases: > + * 1. Not DMA-able device. > + * 2. DMA-able device, but missing _CCA object. > + * > + * In both cases, we will default to dma non-coherent. > + */ > + cca = 0; > + } else { > + /* > + * If architecture does not specify that device must > + * specify ACPI _CCA (e.g. x86), we default to use > + * dma coherent. > + */ > + cca = 1; > + } >
What does it mean here if a device does DMA but is not coherent? Do you have an example of a server that needs this?
Can we please make the default for ARM64 cca=1 as well?
Arnd
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