asoc/multi-component: fsl: add support for variable SSI FIFO depth

Add code that programs the DMA and SSI controllers differently based on the
FIFO depth of the SSI.

The SSI devices on the MPC8610 and the P1022 are identical in every way except
one: the transmit and receive FIFO depth.  On the MPC8610, the depth is eight.
On the P1022, it's fifteen.  The device tree nodes for the SSI include a
"fsl,fifo-depth" property that specifies the FIFO depth.

Signed-off-by: Timur Tabi <timur@freescale.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>

1 files changed, 22 insertions, 3 deletions

diff --git a/sound/soc/fsl/fsl_ssi.c b/sound/soc/fsl/fsl_ssi.c
index 7939c337ed9d..d1c855ade8fb 100644
--- a/sound/soc/fsl/fsl_ssi.c
+++ b/sound/soc/fsl/fsl_ssi.c
@@ -93,6 +93,7 @@ struct fsl_ssi_private {
 	unsigned int playback;
 	unsigned int capture;
 	int asynchronous;
+	unsigned int fifo_depth;
 	struct snd_soc_dai_driver cpu_dai_drv;
 	struct device_attribute dev_attr;
 	struct platform_device *pdev;
@@ -337,11 +338,20 @@ static int fsl_ssi_startup(struct snd_pcm_substream *substream,
 
 		/*
 		 * Set the watermark for transmit FIFI 0 and receive FIFO 0. We
-		 * don't use FIFO 1.  Since the SSI only supports stereo, the
-		 * watermark should never be an odd number.
+		 * don't use FIFO 1.  We program the transmit water to signal a
+		 * DMA transfer if there are only two (or fewer) elements left
+		 * in the FIFO.  Two elements equals one frame (left channel,
+		 * right channel).  This value, however, depends on the depth of
+		 * the transmit buffer.
+		 *
+		 * We program the receive FIFO to notify us if at least two
+		 * elements (one frame) have been written to the FIFO.  We could
+		 * make this value larger (and maybe we should), but this way
+		 * data will be written to memory as soon as it's available.
 		 */
 		out_be32(&ssi->sfcsr,
-			 CCSR_SSI_SFCSR_TFWM0(6) | CCSR_SSI_SFCSR_RFWM0(2));
+			CCSR_SSI_SFCSR_TFWM0(ssi_private->fifo_depth - 2) |
+			CCSR_SSI_SFCSR_RFWM0(ssi_private->fifo_depth - 2));
 
 		/*
 		 * We keep the SSI disabled because if we enable it, then the
@@ -622,6 +632,7 @@ static int __devinit fsl_ssi_probe(struct of_device *of_dev,
 	struct device_attribute *dev_attr = NULL;
 	struct device_node *np = of_dev->dev.of_node;
 	const char *p, *sprop;
+	const uint32_t *iprop;
 	struct resource res;
 	char name[64];
 
@@ -678,6 +689,14 @@ static int __devinit fsl_ssi_probe(struct of_device *of_dev,
 	else
 		ssi_private->cpu_dai_drv.symmetric_rates = 1;
 
+	/* Determine the FIFO depth. */
+	iprop = of_get_property(np, "fsl,fifo-depth", NULL);
+	if (iprop)
+		ssi_private->fifo_depth = *iprop;
+	else
+                /* Older 8610 DTs didn't have the fifo-depth property */
+		ssi_private->fifo_depth = 8;
+
 	/* Initialize the the device_attribute structure */
 	dev_attr = &ssi_private->dev_attr;
 	dev_attr->attr.name = "statistics";