Messages in this thread | | | Subject | Re: [alsa-devel] [PATCH linux-next v2 9/9] ASoC: rsnd: add busif property to dai stream | From | Jiada Wang <> | Date | Tue, 9 Oct 2018 16:09:05 +0900 |
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Hi Morimoto-san
Thanks for your comment
On 2018/10/09 9:44, Kuninori Morimoto wrote: > Hi Jiada > >> SSI can work in following modes >> 1. Basic Mode: (channel 1, 2, 4, 6, 8, 16) >> 2. TDM Extended Mode: (channel 6, 8) >> 3. TDM Split Mode: (channel 1, 2) >> 4. TDM Ex-Split mode: (Channel 2, 4, 6, 8, 10) > (snip) >>> So, my opinions for BUSIFn support are >>> - SSI mode should be selected automatically >> can you give me your idea, how to automatically determine working mode, >> when user plays 2 channel stream on playback dai-link > If my understanding was correct, we can do like this > If DT indicated sound card has dai-link x N, tdm-slots = <M>, > If (N, M) = (1, 2) : Basic mode > If (N, M) = (1, >2): TDM mode > If (N, M) = (2, 4) : TDM Split mode > If (N, M) = (2, >4): TDM Ex-Split mode > If (N, M) = (>2, 8): TDM Split mode > ... > > Maybe some combination was wrong, but we can do something like this ? The idea to consider tdm_slot when determine SSI mode makes sense to me, by checking runtime channel and tdm_slots combination, I think SSI mode can be automatically selected like following:
1ch: (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
>> for example user asks dai-link0 to playback 2ch audio stream, >> driver can't determine which mode to work, as it can be Basic mode, >> Split mode or Ex-Split mode. > Why do we need to use Basic mode if HW has TDM Split mode connection? > If user playbacks 2ch audio in such situation, > we can use TDM Split mode (= only 2ch has sound, other channel has no sound ?) > user might start to playback for other channels. > I'm not sure how it works... >>> - BUSIFn connection should be selected on DT >> since which BUSIFx is used during audio data transfer, is not >> consideration of user, >> I think your previous suggestion, (automatically select BUSIFx) makes >> more sense > I'm not yet sure detail, but in your idea, does it mean, > BUSIFx connection might be exchanged runtime ? no BUSIFx shouldn't be changed during runtime, my idea is BUSIFx can be automatically selected when corresponding dai-link is not active
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
What is your opinion?
Thanks, Jiada > I think BUSIFx connection shouldn't exchanged runtime IMO. > Otherwise, sound position can't be fixed, and user can't control > sound, I think...
> > Best regards > --- > Kuninori Morimoto
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