2013/1/19 Rafał Miłecki zajec5@gmail.com:
Hello,
I'm interested in polishing HDMI audio support for Radeon cards and I hope to get some help here. One of the current problems is that hda has no information about TV audio capabilities. It results in a well known: ALSA sound/pci/hda/hda_eld.c:337 HDMI: ELD buf size is 0, force 128 ALSA sound/pci/hda/hda_eld.c:356 HDMI: invalid ELD data byte 0 It's expected, as radeon (GPU driver) doesn't pass ELD struct anywhere to the GPU and it's not done automatically neither.
Unfortunately it doesn't seem to be trivial to solve. You may be familiar with other GPUs like Nvidia or Intel, where it's done in a pretty simple way, for example:
for (i = 0; i < len; i++) I915_WRITE(hdmiw_hdmiedid, *((uint32_t *)eld + i));
but it can't be handled that way on Radeon cards.
If you take a look at evergreend.h [0] you can see we can't simply write ELD to the GPU buffer, but we have to fill specific registers which look more like SADs (Short Audio Descriptors).
My question is how to handle this on the alsa side. We can't just read ELD, we probably have to read some registers from the audio card. Is something like that implemented anywhere else? Did anyone started working on it? Anyone interested in it?
[0] http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob;f=driver...
I tried hacking this sink info problem again. I've installed "fglrx" on my AMD Radeon HD 6970M (BARTS == DCE5) and verified it sets SAD registers: 5f84 7f077f07 5f88 00500705 5f8c 00000001 5f90 00000001 5f94 00000001 5f98 00000001 5f9c 00c01e05 5fa0 00000001 5fa4 00000001 5fa8 00000607 5fac 00017e07 5fb0 00007e07 5fb4 00000001 5fb8 00000001
Reading ELD of course doesn't work (that's why we get warning in dmesg) and I did some manual confirmation with hda-verb (reading ELD length): $ sudo ./hda-verb /dev/snd/hwC1D0 3 0xf2e 0x8 nid = 0x3, verb = 0xf2e, param = 0x8 value = 0x0
Plus (just for sure) reading first byte of ELD (in case length is always zero, but data is available): $ sudo ./hda-verb /dev/snd/hwC1D0 3 0xf2f 0 | grep val value = 0x0 $ sudo ./hda-verb /dev/snd/hwC1D0 3 0xf2f 1 | grep val value = 0x0 $ sudo ./hda-verb /dev/snd/hwC1D0 3 0xf2f 2 | grep val value = 0x0
So it seems ELD is really not available in this configuration. I thought about vendor specific verbs. Maybe values from the GPU registers are just copied to the audio? I've tried reading every possible vendor specific verb with the attached script (verbs.php).
Unfortunately any verb didn't return anything interesting :(
grep value verbs.txt | sort | uniq -c
9336832 value = 0x0 18432 value = 0x1 6144 value = 0x40 2048 value = 0x415f 55296 value = 0x86 2048 value = 0xa6 16384 value = 0xb6
Does anyone have any idea how we can/should read that values from GPU in the audio driver? :| I guess the must be copied somewhere, but can't find the correct place.