On Mon, Apr 25, 2016 at 03:54:18PM +0200, Lars-Peter Clausen wrote:
> On 04/25/2016 03:39 PM, kernel@xxxxxxxxxxxxxxxx wrote:
> > From: Matthias Reichl <hias@xxxxxxxxx>
> >
> > Register i2s also as pcm device.
>
> This is not really what this patch does.
Agreed, we need a better description.
> > Code ported from bcm2708-i2s driver in Raspberry Pi tree.
> >
> > Signed-off-by: Florian Meier <florian.meier@xxxxxxxx>
> > Signed-off-by: Matthias Reichl <hias@xxxxxxxxx>
> > Signed-off-by: Martin Sperl <kernel@xxxxxxxxxxxxxxxx>
> > ---
> > sound/soc/bcm/bcm2835-i2s.c | 25 ++++++++++++++++++++++++-
> > 1 file changed, 24 insertions(+), 1 deletion(-)
> >
> > diff --git a/sound/soc/bcm/bcm2835-i2s.c b/sound/soc/bcm/bcm2835-i2s.c
> > index a0026e2..8e93295 100644
> > --- a/sound/soc/bcm/bcm2835-i2s.c
> > +++ b/sound/soc/bcm/bcm2835-i2s.c
> > @@ -632,6 +632,27 @@ static const struct snd_soc_component_driver bcm2835_i2s_component = {
> > .name = "bcm2835-i2s-comp",
> > };
> >
> > +static const struct snd_pcm_hardware bcm2835_pcm_hardware = {
> > + .info = SNDRV_PCM_INFO_INTERLEAVED |
> > + SNDRV_PCM_INFO_JOINT_DUPLEX |
> > + SNDRV_PCM_INFO_MMAP |
> > + SNDRV_PCM_INFO_MMAP_VALID,
> > + .formats = SNDRV_PCM_FMTBIT_S16_LE |
> > + SNDRV_PCM_FMTBIT_S24_LE |
> > + SNDRV_PCM_FMTBIT_S32_LE,
> > + .period_bytes_min = 32,
> > + .period_bytes_max = 64 * PAGE_SIZE,
I think it'd be better to use SZ constants instead of x * PAGE_SIZE.
> > + .periods_min = 2,
> > + .periods_max = 255,
> > + .buffer_bytes_max = 128 * PAGE_SIZE,
> > +};
> > +
> > +static const struct snd_dmaengine_pcm_config bcm2835_dmaengine_pcm_config = {
> > + .prepare_slave_config = snd_dmaengine_pcm_prepare_slave_config,
> > + .pcm_hardware = &bcm2835_pcm_hardware,
> > + .prealloc_buffer_size = 256 * PAGE_SIZE,
> > +};
>
> The generic dmaengine PCM driver auto-discovers these things, no need to
> provide them. The code is OK as it is.
With the auto-discover code we loose the S16_LE format.
If I understood the code in dmaengine_pcm_set_runtime_hwparams
correctly, this is because the DMA controller doesn't support
16bit transfers (only multiples of 32bit are allowed).
But since the I2S driver needs exactly 2 channels S16_LE actually
works fine (one 32bit transfer per frame).
Do you know of a better way to get S16_LE support? It could well
be that I missed something important...
> > +
> > static int bcm2835_i2s_probe(struct platform_device *pdev)
> > {
> > struct bcm2835_i2s_dev *dev;
> > @@ -704,7 +725,9 @@ static int bcm2835_i2s_probe(struct platform_device *pdev)
> > return ret;
> > }
> >
> > - ret = devm_snd_dmaengine_pcm_register(&pdev->dev, NULL, 0);
> > + ret = devm_snd_dmaengine_pcm_register(
> > + &pdev->dev, &bcm2835_dmaengine_pcm_config,
> > + SND_DMAENGINE_PCM_FLAG_COMPAT);
> > if (ret) {
> > dev_err(&pdev->dev, "Could not register PCM: %d\n", ret);
> > return ret;
> >
>
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