diff options
Diffstat (limited to 'sound/soc/fsl/fsl_dma.c')
| -rw-r--r-- | sound/soc/fsl/fsl_dma.c | 67 |
1 files changed, 51 insertions, 16 deletions
diff --git a/sound/soc/fsl/fsl_dma.c b/sound/soc/fsl/fsl_dma.c index 5a6f56d63756..f039e8db0765 100644 --- a/sound/soc/fsl/fsl_dma.c +++ b/sound/soc/fsl/fsl_dma.c @@ -60,6 +60,7 @@ struct dma_object { struct snd_soc_platform_driver dai; dma_addr_t ssi_stx_phys; dma_addr_t ssi_srx_phys; + unsigned int ssi_fifo_depth; struct ccsr_dma_channel __iomem *channel; unsigned int irq; bool assigned; @@ -99,6 +100,7 @@ struct fsl_dma_private { unsigned int irq; struct snd_pcm_substream *substream; dma_addr_t ssi_sxx_phys; + unsigned int ssi_fifo_depth; dma_addr_t ld_buf_phys; unsigned int current_link; dma_addr_t dma_buf_phys; @@ -439,6 +441,7 @@ static int fsl_dma_open(struct snd_pcm_substream *substream) else dma_private->ssi_sxx_phys = dma->ssi_srx_phys; + dma_private->ssi_fifo_depth = dma->ssi_fifo_depth; dma_private->dma_channel = dma->channel; dma_private->irq = dma->irq; dma_private->substream = substream; @@ -552,11 +555,11 @@ static int fsl_dma_hw_params(struct snd_pcm_substream *substream, struct device *dev = rtd->platform->dev; /* Number of bits per sample */ - unsigned int sample_size = + unsigned int sample_bits = snd_pcm_format_physical_width(params_format(hw_params)); /* Number of bytes per frame */ - unsigned int frame_size = 2 * (sample_size / 8); + unsigned int sample_bytes = sample_bits / 8; /* Bus address of SSI STX register */ dma_addr_t ssi_sxx_phys = dma_private->ssi_sxx_phys; @@ -596,7 +599,7 @@ static int fsl_dma_hw_params(struct snd_pcm_substream *substream, * that offset here. While we're at it, also tell the DMA controller * how much data to transfer per sample. */ - switch (sample_size) { + switch (sample_bits) { case 8: mr |= CCSR_DMA_MR_DAHTS_1 | CCSR_DMA_MR_SAHTS_1; ssi_sxx_phys += 3; @@ -610,22 +613,42 @@ static int fsl_dma_hw_params(struct snd_pcm_substream *substream, break; default: /* We should never get here */ - dev_err(dev, "unsupported sample size %u\n", sample_size); + dev_err(dev, "unsupported sample size %u\n", sample_bits); return -EINVAL; } /* - * BWC should always be a multiple of the frame size. BWC determines - * how many bytes are sent/received before the DMA controller checks the - * SSI to see if it needs to stop. For playback, the transmit FIFO can - * hold three frames, so we want to send two frames at a time. For - * capture, the receive FIFO is triggered when it contains one frame, so - * we want to receive one frame at a time. + * BWC determines how many bytes are sent/received before the DMA + * controller checks the SSI to see if it needs to stop. BWC should + * always be a multiple of the frame size, so that we always transmit + * whole frames. Each frame occupies two slots in the FIFO. The + * parameter for CCSR_DMA_MR_BWC() is rounded down the next power of two + * (MR[BWC] can only represent even powers of two). + * + * To simplify the process, we set BWC to the largest value that is + * less than or equal to the FIFO watermark. For playback, this ensures + * that we transfer the maximum amount without overrunning the FIFO. + * For capture, this ensures that we transfer the maximum amount without + * underrunning the FIFO. + * + * f = SSI FIFO depth + * w = SSI watermark value (which equals f - 2) + * b = DMA bandwidth count (in bytes) + * s = sample size (in bytes, which equals frame_size * 2) + * + * For playback, we never transmit more than the transmit FIFO + * watermark, otherwise we might write more data than the FIFO can hold. + * The watermark is equal to the FIFO depth minus two. + * + * For capture, two equations must hold: + * w > f - (b / s) + * w >= b / s + * + * So, b > 2 * s, but b must also be <= s * w. To simplify, we set + * b = s * w, which is equal to + * (dma_private->ssi_fifo_depth - 2) * sample_bytes. */ - if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) - mr |= CCSR_DMA_MR_BWC(2 * frame_size); - else - mr |= CCSR_DMA_MR_BWC(frame_size); + mr |= CCSR_DMA_MR_BWC((dma_private->ssi_fifo_depth - 2) * sample_bytes); out_be32(&dma_channel->mr, mr); @@ -879,6 +902,7 @@ static int __devinit fsl_soc_dma_probe(struct of_device *of_dev, struct device_node *np = of_dev->dev.of_node; struct device_node *ssi_np; struct resource res; + const uint32_t *iprop; int ret; /* Find the SSI node that points to us. */ @@ -889,15 +913,17 @@ static int __devinit fsl_soc_dma_probe(struct of_device *of_dev, } ret = of_address_to_resource(ssi_np, 0, &res); - of_node_put(ssi_np); if (ret) { - dev_err(&of_dev->dev, "could not determine device resources\n"); + dev_err(&of_dev->dev, "could not determine resources for %s\n", + ssi_np->full_name); + of_node_put(ssi_np); return ret; } dma = kzalloc(sizeof(*dma) + strlen(np->full_name), GFP_KERNEL); if (!dma) { dev_err(&of_dev->dev, "could not allocate dma object\n"); + of_node_put(ssi_np); return -ENOMEM; } @@ -910,6 +936,15 @@ static int __devinit fsl_soc_dma_probe(struct of_device *of_dev, dma->ssi_stx_phys = res.start + offsetof(struct ccsr_ssi, stx0); dma->ssi_srx_phys = res.start + offsetof(struct ccsr_ssi, srx0); + iprop = of_get_property(ssi_np, "fsl,fifo-depth", NULL); + if (iprop) + dma->ssi_fifo_depth = *iprop; + else + /* Older 8610 DTs didn't have the fifo-depth property */ + dma->ssi_fifo_depth = 8; + + of_node_put(ssi_np); + ret = snd_soc_register_platform(&of_dev->dev, &dma->dai); if (ret) { dev_err(&of_dev->dev, "could not register platform\n"); |