On 10/12/2019 14:57, Takashi Iwai wrote:
The HD-audio CORB/RIRB communication was programmed in a way that was documented in the reference in decades ago, which is essentially a polling in the waiter side. It's working fine but costs CPU cycles on some platforms that support only slow communications. Also, for some platforms that had unreliable communications, we put longer wait time (2 ms), which accumulate quite long time if you execute many verbs in a shot (e.g. at the initialization or resume phase).
This patch attempts to improve the situation by introducing the standard waitqueue in the RIRB waiter side instead of polling. The test results on my machine show significant improvements. The time spent for "cat /proc/asound/card*/codec#*" were changed like:
Intel SKL + Realtek codec before the patch: 0.00user 0.04system 0:00.10elapsed 40.0%CPU after the patch: 0.00user 0.01system 0:00.10elapsed 10.0%CPU
Nvidia GP107GL + Nvidia HDMI codec before the patch: 0.00user 0.00system 0:02.76elapsed 0.0%CPU after the patch: 0.00user 0.00system 0:00.01elapsed 17.0%CPU
So, for Intel chips, the total time is same, while the total time is greatly reduced (from 2.76 to 0.01s) for Nvidia chips. The only negative data here is the increase of CPU time for Nvidia, but this is the unavoidable cost for faster wakeups, supposedly.
Signed-off-by: Takashi Iwai tiwai@suse.de
Starting with next-20191217 I am seeing the following error on one of our Tegra platforms ...
tegra-hda 3510000.hda: azx_get_response timeout, switching to polling mode: last cmd=0x404f2d00
Bisect is point to this commit and although it does not cleanly revert, if I revert this and a couple dependencies on top of -next the issue goes away. Any thoughts on what could be going on here?
Cheers Jon