RE: [alsa-devel] [PATCH] ASoC: atmel_ssc_dai: Track playback and capture CMR dividers separately.

From: Peter Rosin
Date: Tue Oct 21 2014 - 03:57:26 EST

Hi!

(and thank you for the pointer to the example with the ssc-dai in master mode)

> Hi Peter,
>
> On 10/20/2014 09:45 PM, Peter Rosin wrote:
> > From 1e5621d7b9887c648d1a66238dc82d715c1e2cad Mon Sep 17 00:00:00
> > 2001
> > From: Peter Rosin <peda@xxxxxxxxxx>
> > Date: Mon, 20 Oct 2014 14:38:04 +0200
> > Subject: [PATCH] ASoC: atmel_ssc_dai: Track playback and capture CMR
> dividers
> > separately.
> >
> > The CMR divider register is shared by playback and capture. The SSC
> > driver therefore tries to enforce rules so that the needed register
> > content do not conflict during simultaneous playback/capture. However,
> > the implementation also prevents changing the register content in a
> > half-duplex scenario, which is needed when changing sample rates.
>
> I am not fully get what you mean here, do you mean:
> - when playback, first playback 48kHz, and then playback 8Khz, the 8Khz still
> playback in 48kHz mode?
>
> or other things?

I do not know exactly why the problem occurs, but it might be connected to
the library (proprietary) we are using. It apparently uses the OSS interface
and somehow it opens a stream and changes the playback sample-rate a
couple of time before it settles on something. I don't know why this is
done, and I have no control over it. The end result is that without this patch,
the ssc-dai driver returns -EBUSY when the library changes the playback
sample-rate (the driver returns -EBUSY because it thinks that the new
sample rate does not match a previously given capture sample-rate, but
that is of course bogus when no capture is going on at all).

> > Thus, keep track of the desired playback and capture clock dividers
> > separately, and allow changing rates without closing the stream.
> >
> > Signed-off-by: Peter Rosin <peda@xxxxxxxxxx>
> > ---
> > sound/soc/atmel/atmel_ssc_dai.c | 31 ++++++++++++++++++++++------
> ---
> > sound/soc/atmel/atmel_ssc_dai.h | 10 ++++++----
> > 2 files changed, 28 insertions(+), 13 deletions(-)
> >
> > diff --git a/sound/soc/atmel/atmel_ssc_dai.c
> > b/sound/soc/atmel/atmel_ssc_dai.c index f403f39..fec14fb 100644
> > --- a/sound/soc/atmel/atmel_ssc_dai.c
> > +++ b/sound/soc/atmel/atmel_ssc_dai.c
> > @@ -277,7 +277,8 @@ static void atmel_ssc_shutdown(struct
> snd_pcm_substream *substream,
> > /* Reset the SSC */
> > ssc_writel(ssc_p->ssc->regs, CR, SSC_BIT(CR_SWRST));
> > /* Clear the SSC dividers */
> > - ssc_p->cmr_div = ssc_p->tcmr_period = ssc_p->rcmr_period
> = 0;
> > + ssc_p->tcmr_div = ssc_p->rcmr_div = 0;
> > + ssc_p->tcmr_period = ssc_p->rcmr_period = 0;
> > }
> > spin_unlock_irq(&ssc_p->lock);
> > }
> > @@ -304,17 +305,27 @@ static int atmel_ssc_set_dai_clkdiv(struct
> snd_soc_dai *cpu_dai,
> > struct atmel_ssc_info *ssc_p = &ssc_info[cpu_dai->id];
> >
> > switch (div_id) {
> > - case ATMEL_SSC_CMR_DIV:
> > + case ATMEL_SSC_TCMR_DIV:
> > /*
> > * The same master clock divider is used for both
> > * transmit and receive, so if a value has already
> > - * been set, it must match this value.
> > + * been set for the other direction, it must match
> > + * this value.
> > */
> > - if (ssc_p->cmr_div == 0)
> > - ssc_p->cmr_div = div;
> > - else
> > - if (div != ssc_p->cmr_div)
> > - return -EBUSY;
> > + if (ssc_p->rcmr_div == 0)
> > + ssc_p->tcmr_div = div;
> > + else if (div != ssc_p->rcmr_div)
> > + return -EBUSY;
> > + break;
> > +
> > + case ATMEL_SSC_RCMR_DIV:
> > + /*
> > + * See ATMEL_SSC_TCMR_DIV.
> > + */
> > + if (ssc_p->tcmr_div == 0)
> > + ssc_p->rcmr_div = div;
> > + else if (div != ssc_p->tcmr_div)
> > + return -EBUSY;
> > break;
> >
> > case ATMEL_SSC_TCMR_PERIOD:
> > @@ -345,6 +356,7 @@ static int atmel_ssc_hw_params(struct
> snd_pcm_substream *substream,
> > struct atmel_pcm_dma_params *dma_params;
> > int dir, channels, bits;
> > u32 tfmr, rfmr, tcmr, rcmr;
> > + u16 cmr;
>
> should be u32.

Ok, I'll send an updated patch later.

> > int start_event;
> > int ret;
> > int fslen, fslen_ext;
> > @@ -626,7 +638,8 @@ static int atmel_ssc_hw_params(struct
> snd_pcm_substream *substream,
> > }
> >
> > /* set SSC clock mode register */
> > - ssc_writel(ssc_p->ssc->regs, CMR, ssc_p->cmr_div);
> > + cmr = ssc_p->tcmr_div ? ssc_p->tcmr_div : ssc_p->rcmr_div;
> > + ssc_writel(ssc_p->ssc->regs, CMR, cmr);
> >
> > /* set receive clock mode and format */
> > ssc_writel(ssc_p->ssc->regs, RCMR, rcmr); diff --git
> > a/sound/soc/atmel/atmel_ssc_dai.h b/sound/soc/atmel/atmel_ssc_dai.h
> > index b1f08d5..a25df7a 100644
> > --- a/sound/soc/atmel/atmel_ssc_dai.h
> > +++ b/sound/soc/atmel/atmel_ssc_dai.h
> > @@ -39,9 +39,10 @@
> > #define ATMEL_SYSCLK_MCK 0 /* SSC uses AT91 MCK as system
> clock */
> >
> > /* SSC divider ids */
> > -#define ATMEL_SSC_CMR_DIV 0 /* MCK divider for BCLK */
> > -#define ATMEL_SSC_TCMR_PERIOD 1 /* BCLK divider for transmit FS */
> > -#define ATMEL_SSC_RCMR_PERIOD 2 /* BCLK divider for receive FS */
> > +#define ATMEL_SSC_TCMR_DIV 0 /* MCK divider for transmit BCLK */
> > +#define ATMEL_SSC_RCMR_DIV 1 /* MCK divider for receive BCLK */
> > +#define ATMEL_SSC_TCMR_PERIOD 2 /* BCLK divider for transmit
> FS */
> > +#define ATMEL_SSC_RCMR_PERIOD 3 /* BCLK divider for receive
> FS */
> > /*
> > * SSC direction masks
> > */
> > @@ -110,7 +111,8 @@ struct atmel_ssc_info {
> > unsigned short dir_mask; /* 0=unused, 1=playback, 2=capture
> */
> > unsigned short initialized; /* true if SSC has been initialized */
> > unsigned short daifmt;
> > - unsigned short cmr_div;
> > + unsigned short tcmr_div;
> > + unsigned short rcmr_div;
> > unsigned short tcmr_period;
> > unsigned short rcmr_period;
> > struct atmel_pcm_dma_params *dma_params[2];
> >
>
> Best Regards,
> Bo Shen

Cheers,
Peter

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/