Hi Matt,
please include me in CC, your emails don't seem to get through linux-rpi-kernel reliably.
I did a few tests with WM5102 in DSP A mode connected to RPi3 with downstream kernel 4.9.11 plus your patch. wm5102 was configured as master, cpu<->codec dai_link.dai_fmt = SND_SOC_DAIFMT_DSP_A | SND_SOC_DAIFMT_NB_NF | SND_SOC_DAIFMT_CBM_CFM
Comments are inline.
On Wed, Feb 22, 2017 at 05:56:40PM +1100, Matt Flax wrote:
This patch adds multitrack capability if in DSP mode A and the codec is master.
In bcm2835_i2s_startup, snd_pcm_hw_constraint_single is used to set channels to 8 if both SND_SOC_DAIFMT_CBM_CFM and SND_SOC_DAIFMT_DSP_A are set. Otherwise, channels are set to 2. These settings are accomplished using the SNDRV_PCM_HW_PARAM_CHANNELS variable.
In bcm2835_i2s_shutdown the channels are set to 2 by default.
In bcm2835_i2s_hw_params, DSP mode A format is now an option. Before replicating the format variable (from ch2 to ch1) for register loading, requested channels are checked to be either 2 or 8. This can be expanded later to accomodate other channel counts if supported by the sound card hardware.
Signed-off-by: Matt Flax <flatmax at flatmax.org>
sound/soc/bcm/bcm2835-i2s.c | 22 +++++++++++++++++----- 1 file changed, 17 insertions(+), 5 deletions(-)
diff --git a/sound/soc/bcm/bcm2835-i2s.c b/sound/soc/bcm/bcm2835-i2s.c index 6ba2049..4b5f3f1 100644 --- a/sound/soc/bcm/bcm2835-i2s.c +++ b/sound/soc/bcm/bcm2835-i2s.c @@ -296,6 +296,7 @@ static int bcm2835_i2s_hw_params(struct snd_pcm_substream *substream,
switch (dev->fmt & SND_SOC_DAIFMT_FORMAT_MASK) { case SND_SOC_DAIFMT_I2S:
- case SND_SOC_DAIFMT_DSP_A: data_delay = 1;
In DSP_A mode data_delay should be set to 0. With data_delay = 1 the MSB is transmitted 1 clock cycle too late and the LSB of the previous sample is received as MSB (i.e. you get loud noise).
See these screenshots, I2S data was 0xF000 (S16_LE format)
data_delay = 1: http://www.horus.com/~hias/tmp/rpi/bcm2835-dsp-a-delay-1.png
data_delay = 0: http://www.horus.com/~hias/tmp/rpi/bcm2835-dsp-a-delay-0.png
break;default: @@ -312,6 +313,7 @@ static int bcm2835_i2s_hw_params(struct snd_pcm_substream *substream,
switch (params_channels(params)) { case 2:
- case 8: format = BCM2835_I2S_CH1(format) | BCM2835_I2S_CH2(format); format |= BCM2835_I2S_CH1(BCM2835_I2S_CHPOS(ch1pos)); format |= BCM2835_I2S_CH2(BCM2835_I2S_CHPOS(ch2pos));
@@ -526,7 +528,17 @@ static int bcm2835_i2s_startup(struct snd_pcm_substream *substream, regmap_update_bits(dev->i2s_regmap, BCM2835_I2S_CS_A_REG, BCM2835_I2S_STBY, BCM2835_I2S_STBY);
- return 0;
- /* Set the max channels to 8 if the codec is master and
* we are in DSP A mode. Otherwise only allow 2 channels.*/- if ((dev->fmt &
(SND_SOC_DAIFMT_MASTER_MASK | SND_SOC_DAIFMT_FORMAT_MASK))== (SND_SOC_DAIFMT_CBM_CFM | SND_SOC_DAIFMT_DSP_A))return snd_pcm_hw_constraint_single(substream->runtime,SNDRV_PCM_HW_PARAM_CHANNELS, 8);
I'm not sure why you are limiting to exactly 8 channels. 2 channels worked fine here, too. Haven't tested with 4 or 6 channels yet but I guess any even number of channels should work.
In 8-channel configuration I often got swapped/shifted channels. Not 100% sure why, but probably because bcm2835 hadn't DMAed the data in when the codec started the clocks - in that case bcm2835 seems to repeat the last stereo frame data it had in it's buffer. I haven't digged into that deeper though, could be something in my test setup as well.
- else
return snd_pcm_hw_constraint_single(substream->runtime,SNDRV_PCM_HW_PARAM_CHANNELS, 2);}
static void bcm2835_i2s_shutdown(struct snd_pcm_substream *substream, @@ -549,6 +561,10 @@ static void bcm2835_i2s_shutdown(struct snd_pcm_substream *substream, * not stop the clock when SND_SOC_DAIFMT_CONT */ bcm2835_i2s_stop_clock(dev);
- /* Default to 2 channels */
- snd_pcm_hw_constraint_single(substream->runtime,
SNDRV_PCM_HW_PARAM_CHANNELS, 2);}
static const struct snd_soc_dai_ops bcm2835_i2s_dai_ops = { @@ -576,16 +592,12 @@ static struct snd_soc_dai_driver bcm2835_i2s_dai = { .name = "bcm2835-i2s", .probe = bcm2835_i2s_dai_probe, .playback = {
.channels_min = 2,.channels_max = 2,.channels_min = 2,.channels_max = 2,
With .channels_max removed I get no alsa PCMs with the downstream card drivers - "aplay -L" only reported the "null" PCM.
Changing that to .channels_min = 2, .channels_max = 8 brought back the PCMs.
so long,
Hias