The dmix plugin has some optimized implementations for x86 using the
direct memory accesses, which was rather the original version, in
addition to the "generic" implementation using the semaphore
blocking. The x86 implementation relies on the memory coherency *and*
the fast read/write on it.
For other architectures, this has been always disabled just because of
memory coherency. But, the recent LPE audio development revealed
that, even on x86 platforms, the read/write performance might become
extremely bad when the buffer is marked as uncached. Some drivers
already know the buffer is uncached, we need to switch to the generic
mode in such a case.
This patch introduces yet another flag to dmix configuration,
direct_memory_access, that indicates whether the x86-specific
optimization can be used or not. Each driver can set the flag in its
cards config namespace, and the default dmix config refers to it.
As of this patch, only HDMI LPE Audio driver sets it.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
It's a playback-only device with a single PCM dedicated for HDMI/DP
output. The dmix is working with the latest driver code, so enable it
for default, while providing the hdmi PCM dev for the accesses with
AES bits.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
