Re: [alsa-devel] [PATCH linux-next v2 9/9] ASoC: rsnd: add busif property to dai stream

From: Jiada Wang
Date: Tue Oct 09 2018 - 06:41:07 EST


Hi Morimoto-san

Thanks for your feedback

On 2018/10/09 16:47, Kuninori Morimoto wrote:
Hi Jiada

Thanks for your feedback

1ch:Â (tdm_slots < 4) Basic mode, (tdm_slots >= 4) TDM Split mode
2ch: (2 <= tdm_slots < 8) Basic mode, (tdm_slots >= 8) TDM Ex-Split mode
4ch: (4 <= tdm_slots < 8) Basic mode, (tdm_slots >= 8) TDM Ex-Split mode
6ch: (6 <= tdm_slots < 8) Basic mode, (tdm_slots == 8) TDM Extended
mode, (8 < tdm_slots) TDM Ex-Split mode
8ch: (6 <= tdm_slots < 8) TDM Extended mode, (8 <= tdm_slots < 16)
Basic mode, (tdm_slots == 16) TDM Ex-Split
10ch: TDM Ex-Split mode
16ch: Basic Mode
Sorry, but I couldn't understand what this table means ?
For example, what does "1ch" mean ?
It looks like "1ch playback by TDM"...
sorry for vague explanation,
by "1ch" I mean runtime 1 channel playback
for example:
if user plays 1 channel stream, by checking tdm_slots value,
if it is < 4, then it can't be working in Split mode, so driver will
automatically set SSI to work in Basic mode, otherwise, SSI will
work in TDM Split mode.

The reason I added rsnd_ssi_select_busif(io, chan) in rsnd_hw_params()
in patch ASoC: rsnd: add busif property to dai stream of v2 patch-set,
is because runtime channel is necessary information to determine which
BUSIFx to select,
(which is mentioned in above)
and at this stage (rsnd_hw_params()), all other control settings
(register setting, dma address calculation etc)
haven't been done, so corresponding dai-link can be considered to be
not active at this timing
but maybe you have better suggestion when to automatically select BUSIFx
My image is like this.

sound {
compatible = "simple-scu-audio-card or new card";
...
simple-audio-card,convert-channels = <8>;
...
busif0: simple-audio-card,cpu@0 { sound-dai = <&rcar_sound 0>; };
busif1: simple-audio-card,cpu@1 { sound-dai = <&rcar_sound 1>; };
busif2: simple-audio-card,cpu@2 { sound-dai = <&rcar_sound 2>; };
busif3: simple-audio-card,cpu@3 { sound-dai = <&rcar_sound 3>; };
simple-audio-card,codec { sound-dai = <&xxx>; };
};

rcar_sound {
dai0 { playback = <&ssiu0 ssi0>; }
dai1 { playback = <&ssiu1 ssi0>; }
dai2 { playback = <&ssiu2 ssi0>; }
dai3 { playback = <&ssiu3 ssi0>; }
};
After re-think about BUSIFx selection, I agree with you,
it shouldn't be random, and select it via device-tree, as you have already demonstrated
is a good idea

Based on our discussion so far, I think we both agree on the following points
1. Driver select SSI mode automatically (by checking tdm_slots, runtime channel, etc)
2. Driver parse BUSIFx for each dai-link from device-tree

I will review my v2 patch-set, drop changes violate to above two points


Thanks,
Jiada
Best regards
---
Kuninori Morimoto