On Tue, Jun 08, 2021 at 09:20:29AM +0800, Jason Wang wrote: > " > > 6.2.17 _CCA (Cache Coherency Attribute) The _CCA object returns whether or > not a bus-master device supports hardware managed cache coherency. Expected > values are 0 to indicate it is not supported, and 1 to indicate that it is > supported. All other values are reserved. > > ... > > On Intel platforms, if the _CCA object is not supplied, the OSPM will assume > the devices are hardware cache coherent. > > " _CCA is mostly used on arm/arm64 platforms to figure out if a device needs non-coherent DMA handling in the DMA API or not. It is not related to the NoSnoop TLPs that override the setting for an otherwise coherent device.
