[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <3d4f89e8-ce41-f4eb-8e1b-b05c962bcea7@opensource.cirrus.com>
Date: Wed, 22 Feb 2023 11:39:55 +0000
From: Richard Fitzgerald <rf@...nsource.cirrus.com>
To: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
<broonie@...nel.org>, <cezary.rojewski@...el.com>,
<peter.ujfalusi@...ux.intel.com>,
<yung-chuan.liao@...ux.intel.com>, <kai.vehmanen@...ux.intel.com>
CC: <alsa-devel@...a-project.org>, <linux-kernel@...r.kernel.org>,
<patches@...nsource.cirrus.com>
Subject: Re: [PATCH 09/10] ASoC: Intel: sof_sdw: Add support for Cirrus Logic
CS35L56
On 21/02/2023 18:03, Pierre-Louis Bossart wrote:
>
>>>> + card->components);
>>>> + if (!card->components)
>>>> + return -ENOMEM;
>>>> +
>>>> + ret = snd_soc_dapm_new_controls(&card->dapm,
>>>> + cs35l56_sof_widgets,
>>>> ARRAY_SIZE(cs35l56_sof_widgets));
>>>> + if (ret) {
>>>> + dev_err(card->dev, "Widgets add failed: %d\n", ret);
>>>> + return ret;
>>>> + }
>>>> +
>>>> + ret = snd_soc_dapm_add_routes(&card->dapm, cs35l56_sof_map, count);
>>>> + if (ret) {
>>>> + dev_err(card->dev, "Map add %d failed: %d\n", count, ret);
>>>> + return ret;
>>>> + }
>>>> +
>>>> + /* Enable one feedback TX per amp on different slots */
>>>> + for_each_rtd_codec_dais(rtd, i, codec_dai) {
>>>> + ret = snd_soc_dai_set_tdm_slot(codec_dai, 0x3, 1 << i, 4, 16);
>>>
>>> TDM slots? Not getting how this would work with SoundWire?
>>>
>>
>> Strictly speaking Soundwire is TDM (the frame time is divided up into
>> slots for each sample...).
>>
>> The problem is if you have N amps on the dailink all feeding back audio
>> on the same bus. Their DP slots are all programmed to the same positions
>> in the frame, same as for the playback. So you have 4 amps all trying to
>> send 6 audio channels in the same positions in the frame and you'll just
>> get a ton of bus clash interrupts.
>>
>> So we use the set_tdm_slot() like we do with I2S TDM to set which slots
>> are active for each amp.
>>
>> I can't see that there's any obvious "generic" way that the manager code
>> can automatically figure out how many channels to enable on each amp and
>> what order to map them, so we do it here. Just as with I2S TDM - you
>> have many slots and many codecs but the machine driver has to tell it
>> how to map those.
>
> IIRC Bard did the same thing recently, and the order of the feedback
> channels is really defined by the order in which the peripheral devices
> are added in the dailink. See
> https://github.com/thesofproject/linux/pull/4108
>
I don't really see how it is determining how to split the channels.
I see there is a discussion about that but I didn't see any explanation
that I could understand.
Also that only seems to have been done for IPCv4. What if my system
uses IPCv3 ?
Anyway, I'll drop the machine driver patches for now until the IPC code
is stable and consistent behavior for v3 and v4.
> There's also another open related to the number of channels, we need to
> patch what the CPU DAI can handle, see
> https://github.com/thesofproject/linux/pull/4136 or
> https://github.com/thesofproject/linux/pull/4134
Powered by blists - more mailing lists