29.01.2020 17:33, Jon Hunter пишет: > > On 29/01/2020 10:49, Jon Hunter wrote: >> >> On 28/01/2020 12:13, Mark Brown wrote: >>> I really don't understand why this is all taking so long, this thread >>> just seems to be going round in interminable circles long after it >>> looked like the issue was understood. I have to admit I've not read >>> every single message in the thread but it's difficult to see why it >>> doesn't seem to be making any progress. >> >> Sorry about that. On reviewing this with the audio team at NVIDIA, I was >> told we don't support S24_LE for I2S. The reason being that the crossbar >> between the DMA and I2S is not able to extract the correct 24-bits from >> the 32-bit sample to feed to the I2S interface. The Tegra documentation >> does show support for 24-bits, but not state explicit support for S24_LE. >> >> Now Ben says that he has this working, but I am unable to reproduce >> this, so before just dropping the S24_LE support, I would like to >> understand how this is working for Ben in case there is something that >> we have overlooked here. > > Ah, I see that part of the problem is that patches 6 and 7 are yet to be > applied and without these the audio is completely distorted because > there is a mismatch in the data size between the APBIF and I2S > controller. Applying these patches it is not distorted but now I am > observing the clocking issue Ben reported and so the tone is not quite > right. > > Ben, I was able to workaround the clocking issue by making the I2S word > clock 64 bits long and not 48. > > diff --git a/sound/soc/tegra/tegra30_i2s.c b/sound/soc/tegra/tegra30_i2s.c > index bbf81b5aa723..3c9b4779e61b 100644 > --- a/sound/soc/tegra/tegra30_i2s.c > +++ b/sound/soc/tegra/tegra30_i2s.c > @@ -143,7 +143,7 @@ static int tegra30_i2s_hw_params(struct > snd_pcm_substream *substream, > case SNDRV_PCM_FORMAT_S24_LE: > val = TEGRA30_I2S_CTRL_BIT_SIZE_24; > audio_bits = TEGRA30_AUDIOCIF_BITS_24; > - sample_size = 24; > + sample_size = 32; > break; > case SNDRV_PCM_FORMAT_S32_LE: > val = TEGRA30_I2S_CTRL_BIT_SIZE_32; > > For I2S I believe we only care about the edges of the word clock and so > we make the overall period of the word clock 64 bit clocks then we no > longer have an issue with the bit clock frequency. I assume that this > should also be fine for TDM modes as well. > > Can you let me know if this works for you? cat /proc/asound/card0/pcm0p/sub0/hw_params access: MMAP_INTERLEAVED format: S24_LE subformat: STD channels: 2 rate: 48000 (48000/1) period_size: 512 buffer_size: 4096 No distortion at all! Jon, thank you very much!
