El Fri, Jan 05, 2018 at 02:12:42PM -0800 Matthias Kaehlcke ha dit:
> The Rockchip I2S controller only allows to configure even numbers of
> capture channels. It is still possible to capture monophonic audio by
> using dual-channel mode and ignoring the 'data' from the second
> channel.
Due to different issues in our audio recording path I couldn't test
this properly, and only looked at the .wav data in audacity, which
appeared to look ok. After putting some of the missing pieces
together and I noticed that mono capture doesn't work as intended,
the recorded audio is slowed down. I think this is because the I2S
controller keeps generating a two-channel stream, however the sound
system interprets it as a monophonic stream because of the channel
configuration.
Not sure if there is a clean solution for this if we can't tell the
hardware to generate a single-channel stream. Any suggestions or do
we have to revert the patch?
Sorry about the mess :(
> ---
> sound/soc/rockchip/rockchip_i2s.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/sound/soc/rockchip/rockchip_i2s.c b/sound/soc/rockchip/rockchip_i2s.c
> index 908211e1d6fc..cc22ab3d10dd 100644
> --- a/sound/soc/rockchip/rockchip_i2s.c
> +++ b/sound/soc/rockchip/rockchip_i2s.c
> @@ -328,6 +328,7 @@ static int rockchip_i2s_hw_params(struct snd_pcm_substream *substream,
> val |= I2S_CHN_4;
> break;
> case 2:
> + case 1:
> val |= I2S_CHN_2;
> break;
> default:
> @@ -460,7 +461,7 @@ static struct snd_soc_dai_driver rockchip_i2s_dai = {
> },
> .capture = {
> .stream_name = "Capture",
> - .channels_min = 2,
> + .channels_min = 1,
> .channels_max = 2,
> .rates = SNDRV_PCM_RATE_8000_192000,
> .formats = (SNDRV_PCM_FMTBIT_S8 |
> @@ -654,7 +655,7 @@ static int rockchip_i2s_probe(struct platform_device *pdev)
> }
>
> if (!of_property_read_u32(node, "rockchip,capture-channels", &val)) {
> - if (val >= 2 && val <= 8)
> + if (val >= 1 && val <= 8)
> soc_dai->capture.channels_max = val;
> }
>
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