On Wed, Aug 19, 2020 at 02:49:01PM +0200, Tomasz Figa wrote:

With the default config it doesn't, but with
CONFIG_DMA_NONCOHERENT_CACHE_SYNC enabled it makes dma_pgprot() keep
the pgprot value as is, without enforcing coherence attributes.

Which isn't selected on arm64, and that is for a good reason.

AFAIK dma_cache_sync() isn't the only way to perform the cache
synchronization.

Yes, it is the only documented way to do it.  And if you read the whole
series instead of screaming you'd see that it provides a proper way
to deal with non-coherent memory which will also work with arm64.
instead of screaming 

By the way, as a videobuf2 reviewer, I'd appreciate being CC'd on any
series related to the subsystem-facing DMA API changes, since
videobuf2 is one of the biggest users of it.

The cc list is too long - I cc lists and key maintainers.  As a reviewer
should should watch your subsystems lists closely.