[PATCH] drm/radeon/audio: fix missing multichannel PCM SAD in some cases

[Rafał Miłecki]

2013/10/29 Anssi Hannula <anssi.hannula at iki.fi>:
> Because of this, only the 2-channel SAD may be used if it appears before
> the 8-channel SAD. Unless other SADs require otherwise, this may cause
> the ALSA HDA driver to allow stereo playback only.

I can confirm that the problem exists. My SADs (Onkyo TX-SR605):
Format: 1 (PCM)        Channels:1    Freq:0x7F (32-192)    B2:0x07 (16-24b)
Format: 1 (PCM)        Channels:7    Freq:0x7F (32-192)    B2:0x07 (16-24b)
Format: 2 (AC3)        Channels:7    Freq:0x07 (32-48)    B2:0x50 (640?)
Format: 7 (DTS)        Channels:7    Freq:0x06 (44-48)    B2:0xC0 (1536?)
Format: 10 (EAC3)    Channels:7    Freq:0x06 (44-48)    B2:0x00
Format: 11 (DTS_HD)    Channels:7    Freq:0x7E (44-192)    B2:0x01
Format: 12 (MLP)    Channels:7    Freq:0x1E (44-96)    B2:0x00

Unfortunately I get only 1 emulated SAD entry for PCM
(/proc/asound/card1/eld#0.0):
sad0_coding_type        [0x1] LPCM
sad0_channels           2
sad0_rates              [0x1ee0] 32000 44100 48000 88200 96000 176400 192000
sad0_bits               [0xe0000] 16 20 24

So I can not play 8 channel LPCM "legally" (without forcing player to do so).


> Fix the code to pick the PCM SAD with the highest number of channels,
> while merging the rate masks of PCM SADs with lower amount of channels
> into the additional stereo rate mask byte.

Does it mean that now instead of 2 real SADs:
1) 192kHz support for 2 channels
2) 96kHz support for 8 channels
you will only get:
1) 192kHz support for 8 channels
?
Does it mean alsa may try to play 8channels audio at 192kHz and fail at this?
That doesn't sound good, but on the other hand I can't propose
anything better :|
Out of curiosity, what does fglrx set in the verbs?


> Technically there are even more cases to handle (multiple non-PCM SADs
> of the same type, more than two PCM SADs with varying channel counts,
> etc), but those have not actually been encountered in the field and
> handling them would be non-trivial.
>
> Example affected EDID from Onkyo TX-SR674 specifying 192kHz stereo
> support and 96kHz 8-channel support (and other 8-channel compressed
> formats):

-- 
Rafał