[alsa-devel] [PATCH v2 05/11] ASoC: fsl-ssi: Add support for imx-pcm-fiq

[Markus Pargmann]

On Sun, Apr 07, 2013 at 07:18:50PM -0500, Timur Tabi wrote:
> Markus Pargmann wrote:
> >Add support for non-dma pcm for imx platforms with imx-pcm-fiq support.
> >Instead of imx-pcm-audio, in this case imx-pcm-fiq-audio device is added
> >and the SIER flags are set differently.
> 
> So just to be clear, this is interrupt-driven SSI audio?  So you're
> generating an interrupt every time the transmit FIFO goes below the
> threshold?

Yes

> I wonder if it makes sense to enable both FIFOs, so that you take
> half as many interrupts per second.

It looks like imx-pcm-fiq and ssi-fiq.s do not support transmitting
through two FIFOs at the moment.

> 
> >
> >Signed-off-by: Markus Pargmann <mpa at pengutronix.de>
> >---
> >  sound/soc/fsl/fsl_ssi.c | 70 ++++++++++++++++++++++++++++++++++++++++---------
> >  1 file changed, 58 insertions(+), 12 deletions(-)
> >
> >diff --git a/sound/soc/fsl/fsl_ssi.c b/sound/soc/fsl/fsl_ssi.c
> >index 7decbd9..afb5a23 100644
> >--- a/sound/soc/fsl/fsl_ssi.c
> >+++ b/sound/soc/fsl/fsl_ssi.c
> >@@ -120,10 +120,12 @@ struct fsl_ssi_private {
> >
> >  	bool new_binding;
> >  	bool ssi_on_imx;
> >+	bool dma;
> 
> Can you rename this to "use_dma" or something like that?

Done.

> 
> >  	struct clk *clk;
> >  	struct platform_device *imx_pcm_pdev;
> >  	struct imx_pcm_dma_params dma_params_tx;
> >  	struct imx_pcm_dma_params dma_params_rx;
> >+	struct imx_pcm_fiq_params fiq_params;
> >
> >  	struct {
> >  		unsigned int rfrc;
> >@@ -353,7 +355,8 @@ static int fsl_ssi_startup(struct snd_pcm_substream *substream,
> >  		 */
> >
> >  		/* Enable the interrupts and DMA requests */
> >-		write_ssi(SIER_FLAGS, &ssi->sier);
> >+		if (ssi_private->dma)
> >+			write_ssi(SIER_FLAGS, &ssi->sier);
> >
> >  		/*
> >  		 * Set the watermark for transmit FIFI 0 and receive FIFO 0. We
> >@@ -520,6 +523,18 @@ static int fsl_ssi_trigger(struct snd_pcm_substream *substream, int cmd,
> >  		return -EINVAL;
> >  	}
> >
> >+	if (!ssi_private->dma) {
> >+		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
> >+			write_ssi(CCSR_SSI_SOR_TX_CLR, &ssi->sor);
> >+			write_ssi(CCSR_SSI_SIER_TIE | CCSR_SSI_SIER_TFE0_EN,
> >+					&ssi->sier);
> >+		} else {
> >+			write_ssi(CCSR_SSI_SOR_RX_CLR, &ssi->sor);
> >+			write_ssi(CCSR_SSI_SIER_RIE | CCSR_SSI_SIER_RFF0_EN,
> >+					&ssi->sier);
> >+		}
> >+	}
> >+
> >  	return 0;
> >  }
> >
> >@@ -680,6 +695,8 @@ static int fsl_ssi_probe(struct platform_device *pdev)
> >  	       sizeof(fsl_ssi_dai_template));
> >  	ssi_private->cpu_dai_drv.name = ssi_private->name;
> >
> >+	ssi_private->dma = !of_property_read_bool(np, "fsl,imx-fiq");
> 
> Instead of looking for the FIQ property, maybe you should just look
> for the absence of a DMA property/node, and then default to
> interrupts if there is no DMA.  That would make it more generic, and
> even work on non-IMX systems.

I do not think it is possible. For example imx27 ssi does support
DMA but for specific boards we have to use fiq instead (phycore-ac97).
So I would prefer to define the DMA in the chip dtsi file and choose
fiq, if necessary, in the board dts.

Regards,

Markus

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