[PATCH] ASoC: OMAP: Add checking to detect bufferless pcms

[PATCH] ASoC: OMAP: Add checking to detect bufferless pcms

[Joonyoung Shim]

Add checking in hw_params and prepare to detect bufferless pcms(i.e. BT
<--> codec).

Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
---
 sound/soc/omap/omap-pcm.c |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/sound/soc/omap/omap-pcm.c b/sound/soc/omap/omap-pcm.c
index 07cf7f4..6454e15 100644
--- a/sound/soc/omap/omap-pcm.c
+++ b/sound/soc/omap/omap-pcm.c
@@ -87,8 +87,10 @@ static int omap_pcm_hw_params(struct snd_pcm_substream *substream,
 	struct omap_pcm_dma_data *dma_data = rtd->dai->cpu_dai->dma_data;
 	int err = 0;
 
+	/* return if this is a bufferless transfer e.g.
+	 * codec <--> BT codec or GSM modem -- lg FIXME */
 	if (!dma_data)
-		return -ENODEV;
+		return 0;
 
 	snd_pcm_set_runtime_buffer(substream, &substream->dma_buffer);
 	runtime->dma_bytes = params_buffer_bytes(params);
@@ -134,6 +136,11 @@ static int omap_pcm_prepare(struct snd_pcm_substream *substream)
 	struct omap_pcm_dma_data *dma_data = prtd->dma_data;
 	struct omap_dma_channel_params dma_params;
 
+	/* return if this is a bufferless transfer e.g.
+	 * codec <--> BT codec or GSM modem -- lg FIXME */
+	if (!prtd->dma_data)
+		return 0;
+
 	memset(&dma_params, 0, sizeof(dma_params));
 	/*
 	 * Note: Regardless of interface data formats supported by OMAP McBSP
-- 
1.5.6.3

Re: [PATCH] ASoC: OMAP: Add checking to detect bufferless pcms

[Jarkko Nikula]

On Wed, Apr 22, 2009 at 4:56 AM, Joonyoung Shim <jy0922.shim@samsung.com>wrote:

> Add checking in hw_params and prepare to detect bufferless pcms(i.e. BT
> <--> codec).
>
> Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
> ---
>  sound/soc/omap/omap-pcm.c |    9 ++++++++-
>  1 files changed, 8 insertions(+), 1 deletions(-)
>
> diff --git a/sound/soc/omap/omap-pcm.c b/sound/soc/omap/omap-pcm.c
> index 07cf7f4..6454e15 100644
> --- a/sound/soc/omap/omap-pcm.c
> +++ b/sound/soc/omap/omap-pcm.c
> @@ -87,8 +87,10 @@ static int omap_pcm_hw_params(struct snd_pcm_substream
> *substream,
>        struct omap_pcm_dma_data *dma_data = rtd->dai->cpu_dai->dma_data;
>        int err = 0;
>
> +       /* return if this is a bufferless transfer e.g.
> +        * codec <--> BT codec or GSM modem -- lg FIXME */
>        if (!dma_data)
> -               return -ENODEV;
> +               return 0;
>
>
I see exactly similar lines in s3c24xx-pcm.c but don't point now the use
case where this is used and I don't have idea what is this all about.

Is this something where DAI driver or another end of connection is used to
provide clocking and the whole setup is then controlled with ALSA PCM API?
Somehow I have the feeling that would there be a better way to achieve it
than with dummy bufferless transfer?


-- 
Jarkko

Re: [PATCH] ASoC: OMAP: Add checking to detect bufferless pcms

[Mark Brown]

On Wed, Apr 22, 2009 at 11:30:32AM +0300, Jarkko Nikula wrote:
> On Wed, Apr 22, 2009 at 4:56 AM, Joonyoung Shim <jy0922.shim@samsung.com>wrote:

> > +       /* return if this is a bufferless transfer e.g.
> > +        * codec <--> BT codec or GSM modem -- lg FIXME */
> >        if (!dma_data)
> > -               return -ENODEV;
> > +               return 0;

> I see exactly similar lines in s3c24xx-pcm.c but don't point now the use
> case where this is used and I don't have idea what is this all about.

The use case is for dummy DAIs used to represent bluetooth and similar -
they aren't going to do any DMA so don't pass anything to the platform.

> Is this something where DAI driver or another end of connection is used to
> provide clocking and the whole setup is then controlled with ALSA PCM API?
> Somehow I have the feeling that would there be a better way to achieve it
> than with dummy bufferless transfer?

The host isn't transferring any data at all in these cases.  Ideally
we'd support multiple platforms and there'd be a dummy platform driver
to go with the dummy DAI driver.

Re: [PATCH] ASoC: OMAP: Add checking to detect bufferless pcms

[Jarkko Nikula]

On Wed, Apr 22, 2009 at 11:43 AM, Mark Brown <broonie@sirena.org.uk> wrote:

> On Wed, Apr 22, 2009 at 11:30:32AM +0300, Jarkko Nikula wrote:
>
> > Is this something where DAI driver or another end of connection is used
> to
> > provide clocking and the whole setup is then controlled with ALSA PCM
> API?
> > Somehow I have the feeling that would there be a better way to achieve it
> > than with dummy bufferless transfer?
>
> The host isn't transferring any data at all in these cases.  Ideally
> we'd support multiple platforms and there'd be a dummy platform driver
> to go with the dummy DAI driver.
>

Probably it's better to extend this patch to other architectures as well (at
least DaVinci) where possible in order to be more consistent. I just noticed
that also PXA is having the same feature.


-- 
Jarkko

Re: [PATCH] ASoC: OMAP: Add checking to detect bufferless pcms

[Mark Brown]

On Wed, Apr 22, 2009 at 12:01:28PM +0300, Jarkko Nikula wrote:
> On Wed, Apr 22, 2009 at 11:43 AM, Mark Brown <broonie@sirena.org.uk> wrote:

> > The host isn't transferring any data at all in these cases.  Ideally
> > we'd support multiple platforms and there'd be a dummy platform driver
> > to go with the dummy DAI driver.

> Probably it's better to extend this patch to other architectures as well (at
> least DaVinci) where possible in order to be more consistent. I just noticed
> that also PXA is having the same feature.

Yes, though given that it's a bodge at the moment it'd need someone to
go through per architecture and check that the right thing is being
done.

When I've thought about doing it I've always decided it'd probably be
less hassle to fix the core not to need the bodge :/

Re: [PATCH] ASoC: OMAP: Add checking to detect bufferless pcms

[Peter Ujfalusi]

On Wednesday 22 April 2009 11:30:32 ext Jarkko Nikula wrote:
> On Wed, Apr 22, 2009 at 4:56 AM, Joonyoung Shim
> <jy0922.shim@samsung.com<mailto:jy0922.shim@samsung.com>> wrote: Add
> checking in hw_params and prepare to detect bufferless pcms(i.e. BT <-->
> codec).
>
> I see exactly similar lines in s3c24xx-pcm.c but don't point now the use
> case where this is used and I don't have idea what is this all about.
>
> Is this something where DAI driver or another end of connection is used to
> provide clocking and the whole setup is then controlled with ALSA PCM API?
> Somehow I have the feeling that would there be a better way to achieve it
> than with dummy bufferless transfer?

In the twl codec, the BT interface does not have dedicated clock line, but it 
is (re)using the clock lines for the voice PCM interface. So in order to get 
BT data going between the BT and the codec, the voice PCM interface has to 
generate the clocks.

But I think this could be done even without the need for the alsa PCM 
interface, probably well placed DAPM switches would also can take care of 
this?

>
> --
> Jarkko

-- 
Péter

Re: [PATCH] ASoC: OMAP: Add checking to detect bufferless pcms

[Joonyoung Shim]

On 4/22/2009 5:30 PM, Jarkko Nikula wrote:
> On Wed, Apr 22, 2009 at 4:56 AM, Joonyoung Shim <jy0922.shim@samsung.com
> <mailto:jy0922.shim@samsung.com>> wrote:
> 
>     Add checking in hw_params and prepare to detect bufferless pcms(i.e. BT
>     <--> codec).
> 
>     Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com
>     <mailto:jy0922.shim@samsung.com>>
>     ---
>     쟳ound/soc/omap/omap-pcm.c |    9 ++++++++-
>      1 files changed, 8 insertions(+), 1 deletions(-)
> 
>     diff --git a/sound/soc/omap/omap-pcm.c b/sound/soc/omap/omap-pcm.c
>     index 07cf7f4..6454e15 100644
>     --- a/sound/soc/omap/omap-pcm.c
>     +++ b/sound/soc/omap/omap-pcm.c
>     @@ -87,8 +87,10 @@ static int omap_pcm_hw_params(struct
>     snd_pcm_substream *substream,
>           쟳truct omap_pcm_dma_data *dma_data = rtd->dai->cpu_dai->dma_data;
>           쟧nt err = 0;
> 
>     +       /* return if this is a bufferless transfer e.g.
>     +        * codec <--> BT codec or GSM modem -- lg FIXME */
>           쟧f (!dma_data)
>     -               return -ENODEV;
>     +               return 0;
> 
> 
> I see exactly similar lines in s3c24xx-pcm.c but don't point now the use
> case where this is used and I don't have idea what is this all about.
> 
> Is this something where DAI driver or another end of connection is used
> to provide clocking and the whole setup is then controlled with ALSA PCM
> API? Somehow I have the feeling that would there be a better way to
> achieve it than with dummy bufferless transfer?

I tested this patch with the omap3 target having the twl4030 codec. The
twl4030 codec driver supports the voice DAI to transfer pcm data between
modem and codec, and i added for test the dummy voice DAI in machine
driver. To transfer pcm data at modem <--> codec doesn't need DMA.

> 
> 
> -- 
> Jarkko

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