On 6/13/17 7:09 AM, Takashi Sakamoto wrote:
Pierre-Louis,
On Jun 12 2017 21:09, Pierre-Louis Bossart wrote:
If describing the detail design of your hardware, you might get more
helps.
* I intentionally ignore discussion about burstness of data
transmission and accuracy of hwptr.
You are probably reading too much into this.
The intent is to optimize DMA operations where the hardware now knows
both hw_ptr and appl_ptr. there is no use of the .ack() for copies into
intermediate buffers
If this patch included enough explanation about the disadvantage of
rewind operation on your driver and hardware in a point of optimization
for DMA data transmission and power consumption, I would not have driven
my imagination so hard for the reviewing.
Maybe you missed what we wrote in the commit message:
"this can be used by low-level driver to optimize DMA operations
and reduce power consumption."
There will be follow-up patches that make use of this capability on
Intel platforms but for now this is hardware-agnostic.
and the code for rewind on capture is largely for
consistency - we've never seen anyone using rewind on capture on
DSP-based platforms.
I'm not a prophet, and you too. It's not better to change interfaces
with any forecast. Furthermore, once changing interfaces, it affects to
all of applications. Please have enough care of it.
I don't get what you are saying. There is no interface or behavior
change, disabling rewinds is strictly opt-in and controlled from the
application. I was just stating that we have not seen anyone use rewinds
on capture and at this point we have no need to disable non-existent
usages...
# I can imagine a disadvantage of rewind operation for PCM capture
# substream. When rewinding, available space on PCM buffer for data
# transmission from hardware is reduced. Then, even if hardware already
# done sampling, it can't transfer the PCM frames. There's a delay and
# hardware needs extra buffering.
Regards
Takashi Sakamoto
_______________________________________________
Alsa-devel mailing list
Alsa-devel@xxxxxxxxxxxxxxxx
http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
_______________________________________________
Alsa-devel mailing list
Alsa-devel@xxxxxxxxxxxxxxxx
http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
