On Monday 31 May 2010 11:16:50 Ujfalusi Peter (Nokia-D/Tampere) wrote:
...
> @@ -185,33 +231,43 @@ static int omap_mcbsp_dai_startup(struct
> snd_pcm_substream *substream, if (!cpu_dai->active)
> err = omap_mcbsp_request(bus_id);
>
> + /*
> + * OMAP McBSP FIFO is word structured.
> + * McBSP2 has 1024 + 256 = 1280 word long buffer,
> + * McBSP1,3,4,5 has 128 word long buffer
> + * This means that the size of the FIFO depends on the sample format.
> + * For example on McBSP3:
> + * 16bit samples: size is 128 * 2 = 256 bytes
> + * 32bit samples: size is 128 * 4 = 512 bytes
> + * It is simpler to place constraint for buffer and period based on
> + * channels.
> + * McBSP3 as example again (16 or 32 bit samples):
> + * 1 channel (mono): size is 128 frames (128 words)
> + * 2 channels (stereo): size is 128 / 2 = 64 frames (2 * 64 words)
> + * 4 channels: size is 128 / 4 = 32 frames (4 * 32 words)
> + */
> +
> + /*
> + * The first rule is for the buffer size, we should not allow smaller
> + * buffer than the FIFO size to avoid underruns
> + */
> + snd_pcm_hw_rule_add(substream->runtime, 0, SNDRV_PCM_HW_PARAM_CHANNELS,
> + hw_rule_bsize_by_channels, mcbsp_data,
> + SNDRV_PCM_HW_PARAM_BUFFER_SIZE, -1);
> +
Obviously this hw_rule must be moved after checking the CPU type, since it is
only valid for OMAP3 class of devices.
I'll fix this in the v2 series.
I have been testing this on OMAP3...
> if (cpu_is_omap343x()) {
> int dma_op_mode = omap_mcbsp_get_dma_op_mode(bus_id);
> - int max_period;
>
> /*
> - * McBSP2 in OMAP3 has 1024 * 32-bit internal audio buffer.
> - * Set constraint for minimum buffer size to the same than FIFO
> - * size in order to avoid underruns in playback startup because
> - * HW is keeping the DMA request active until FIFO is filled.
> + * In case os threshold mode, the rule will ensure, that the
> + * period size is not bigger than the maximum allowed threshold
> + * value.
> */
> - if (bus_id == 1)
> - snd_pcm_hw_constraint_minmax(substream->runtime,
> - SNDRV_PCM_HW_PARAM_BUFFER_BYTES,
> - 4096, UINT_MAX);
> -
> - if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
> - max_period = omap_mcbsp_get_max_tx_threshold(bus_id);
> - else
> - max_period = omap_mcbsp_get_max_rx_threshold(bus_id);
> -
> - max_period++;
> - max_period <<= 1;
> -
> if (dma_op_mode == MCBSP_DMA_MODE_THRESHOLD)
> - snd_pcm_hw_constraint_minmax(substream->runtime,
> - SNDRV_PCM_HW_PARAM_PERIOD_BYTES,
> - 32, max_period);
> + snd_pcm_hw_rule_add(substream->runtime, 0,
> + SNDRV_PCM_HW_PARAM_CHANNELS,
> + hw_rule_psize_by_channels, substream,
> + SNDRV_PCM_HW_PARAM_PERIOD_SIZE, -1);
> }
>
> return err;
--
Péter
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