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Subject[PATCH v7 3/4] ASoC: fsl_ssi: Add dual fifo mode support
Date
By enabling dual fifo mode, it would allow SSI enter a better performance
to transimit/receive data without occasional hardware underrun/overrun.

Signed-off-by: Nicolin Chen <b42378@freescale.com>
Acked-by: Timur Tabi <timur@tabi.org>
Acked-by: Mark Brown <broonie@linaro.org>
---
sound/soc/fsl/fsl_ssi.c | 27 ++++++++++++++++++++++++++-
1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/sound/soc/fsl/fsl_ssi.c b/sound/soc/fsl/fsl_ssi.c
index 35e2773..f43be6d 100644
--- a/sound/soc/fsl/fsl_ssi.c
+++ b/sound/soc/fsl/fsl_ssi.c
@@ -143,6 +143,7 @@ struct fsl_ssi_private {
bool ssi_on_imx;
bool imx_ac97;
bool use_dma;
+ bool use_dual_fifo;
struct clk *clk;
struct snd_dmaengine_dai_dma_data dma_params_tx;
struct snd_dmaengine_dai_dma_data dma_params_rx;
@@ -413,6 +414,12 @@ static int fsl_ssi_setup(struct fsl_ssi_private *ssi_private)
write_ssi(CCSR_SSI_SOR_WAIT(3), &ssi->sor);
}

+ if (ssi_private->use_dual_fifo) {
+ write_ssi_mask(&ssi->srcr, 0, CCSR_SSI_SRCR_RFEN1);
+ write_ssi_mask(&ssi->stcr, 0, CCSR_SSI_STCR_TFEN1);
+ write_ssi_mask(&ssi->scr, 0, CCSR_SSI_SCR_TCH_EN);
+ }
+
return 0;
}

@@ -480,6 +487,15 @@ static int fsl_ssi_startup(struct snd_pcm_substream *substream,
ssi_private->second_stream = substream;
}

+ /* When using dual fifo mode, it is safer to ensure an even period
+ * size. If appearing to an odd number while DMA always starts its
+ * task from fifo0, fifo1 would be neglected at the end of each
+ * period. But SSI would still access fifo1 with an invalid data.
+ */
+ if (ssi_private->use_dual_fifo)
+ snd_pcm_hw_constraint_step(substream->runtime, 0,
+ SNDRV_PCM_HW_PARAM_PERIOD_SIZE, 2);
+
return 0;
}

@@ -947,7 +963,7 @@ static int fsl_ssi_probe(struct platform_device *pdev)
ssi_private->fifo_depth = 8;

if (of_device_is_compatible(pdev->dev.of_node, "fsl,imx21-ssi")) {
- u32 dma_events[2];
+ u32 dma_events[2], dmas[4];
ssi_private->ssi_on_imx = true;

ssi_private->clk = devm_clk_get(&pdev->dev, NULL);
@@ -1001,6 +1017,15 @@ static int fsl_ssi_probe(struct platform_device *pdev)
dma_events[0], shared ? IMX_DMATYPE_SSI_SP : IMX_DMATYPE_SSI);
imx_pcm_dma_params_init_data(&ssi_private->filter_data_rx,
dma_events[1], shared ? IMX_DMATYPE_SSI_SP : IMX_DMATYPE_SSI);
+ if (!of_property_read_u32_array(pdev->dev.of_node, "dmas", dmas, 4)
+ && dmas[2] == IMX_DMATYPE_SSI_DUAL) {
+ ssi_private->use_dual_fifo = true;
+ /* When using dual fifo mode, we need to keep watermark
+ * as even numbers due to dma script limitation.
+ */
+ ssi_private->dma_params_tx.maxburst &= ~0x1;
+ ssi_private->dma_params_rx.maxburst &= ~0x1;
+ }
} else if (ssi_private->use_dma) {
/* The 'name' should not have any slashes in it. */
ret = devm_request_irq(&pdev->dev, ssi_private->irq,
--
1.8.4



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