See if there is any expert in HDMI sound here ...
I am using a dev board (Wandboard) and getting the sound out through the HDMI interface. All hunky dory, with a small nagging exception: every time a sound is played, the HDMI sound handshake protocol adds a delay of 2-3 seconds in reproducing it, which makes it a killer for what I am developing.
Now, I have investigated the issue and seems to be related (apart from a widespread complaint) to the HDMI kernel handler dropping (or closing) the channel when there is inactivity. Hence, a new handshake needs to be negotiated for each new sound. The timeout, according to my experience, is about 5s or so.
The idea would be to tweak the kernel source to eliminate that timeout, so that the channel stays open all the time. Does anyone here know which source file handles that? All I need is a name, and I can do the rest myself (some pointers would not go amiss either). I've search through the source tree and still haven't found anything.
Any help will be appreciated.
In any case, I don't think this should be only applicable to ARM (although in my particular case is). The way HDMI sound is treated, and whether the sound channel is reopened/close for every sound event should be architecture agnostic, and applicable to every platform - I have not investigated it, but the files located in kernel_imx/sound/soc/imx (which I believe hold the key to this) may be part of the core kernel.
he way HDMI sound is treated, and whether the sound channel is reopened/close for every sound event should be architecture agnostic
I agree, unless it turns out the ARM team have compiled something weird (and different) to the x86 (official) kernel... Until we discover that, we'll assume it's an agnostic issue