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Message-ID: <519CFFDD.4080203@metafoo.de>
Date: Wed, 22 May 2013 19:26:53 +0200
From: Lars-Peter Clausen <lars@...afoo.de>
To: Florian Meier <florian.meier@...lo.de>
CC: Mark Brown <broonie@...nel.org>,
Liam Girdwood <lgirdwood@...il.com>, swarren@...dotorg.org,
alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
linux-rpi-kernel@...ts.infradead.org,
linux-arm-kernel@...ts.infradead.org,
Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.de>
Subject: Re: [PATCH] ASoC: Add support for BCM2708
On 05/22/2013 04:10 PM, Florian Meier wrote:
[...]
> diff --git a/sound/soc/bcm2708/bcm2708-i2s.c b/sound/soc/bcm2708/bcm2708-i2s.c
> new file mode 100644
> index 0000000..a8e995f
> --- /dev/null
> +++ b/sound/soc/bcm2708/bcm2708-i2s.c
> @@ -0,0 +1,964 @@
[...]
> +static int bcm2708_i2s_startup(struct snd_pcm_substream *substream,
> + struct snd_soc_dai *dai)
> +{
> + struct bcm2708_i2s_dev *dev = snd_soc_dai_get_drvdata(dai);
> +
> + if (!dev->first_stream) {
> + dev->first_stream = substream;
> +
> + /* should this still be running stop it */
> + bcm2708_i2s_stop_clock(dev);
> +
> + /* enable PCM block */
> + bcm2708_i2s_set_bits(dev, BCM2708_I2S_CS_A_REG, BCM2708_I2S_EN);
> +
> + /*
> + * Disable STBY
> + * Requires at least 4 PCM clock cycles to take effect
> + */
> + bcm2708_i2s_set_bits(dev, BCM2708_I2S_CS_A_REG,
> + BCM2708_I2S_STBY);
> + } else {
> + struct snd_pcm_runtime *first_runtime =
> + dev->first_stream->runtime;
> +
> + /*
> + * This is the second stream open, so we need to impose
> + * sample size and sampling rate constraints.
> + * This is because frame length and clock cannot be specified
> + * seperately.
> + *
> + * Note that this can cause a race condition if the
> + * second stream is opened before the first stream is
> + * fully initialized. We provide some protection by
> + * checking to make sure the first stream is
> + * initialized, but it's not perfect. ALSA sometimes
> + * re-initializes the driver with a different sample
> + * rate or size. If the second stream is opened
> + * before the first stream has received its final
> + * parameters, then the second stream may be
> + * constrained to the wrong sample rate or size.
> + *
> + * We will continue in case of failure and recheck the
> + * constraint in hw_params.
> + */
> + if (!first_runtime->format) {
> + dev_err(substream->pcm->card->dev,
> + "Set format in %s stream first! "
> + "Initialization may fail.\n",
> + substream->stream ==
> + SNDRV_PCM_STREAM_PLAYBACK
> + ? "capture" : "playback");
> + } else {
> + snd_pcm_hw_constraint_minmax(substream->runtime,
> + SNDRV_PCM_HW_PARAM_FORMAT,
> + first_runtime->format,
> + first_runtime->format);
> + }
> +
> + if (!first_runtime->rate) {
> + dev_err(substream->pcm->card->dev,
> + "Set sampling rate in %s stream first! "
> + "Initialization may fail!\n",
> + substream->stream ==
> + SNDRV_PCM_STREAM_PLAYBACK
> + ? "capture" : "playback");
> + } else {
> + snd_pcm_hw_constraint_minmax(substream->runtime,
> + SNDRV_PCM_HW_PARAM_RATE,
> + first_runtime->rate,
> + first_runtime->rate);
> + }
Setting the symmetric_rates lets the core take care of setting the proper
constraints on the rate. It probably makes sense to also add a
symmetric_formats since this isn't the only driver that has the requirement
that the formats for playback and capture match.
> +
> + dev->second_stream = substream;
> + }
> +
> + snd_soc_dai_set_dma_data(dai, substream,
> + &dev->dma_params[substream->stream]);
> +
> + return 0;
> +}
> +
> +static void bcm2708_i2s_shutdown(struct snd_pcm_substream *substream,
> + struct snd_soc_dai *dai)
> +{
> + struct bcm2708_i2s_dev *dev = snd_soc_dai_get_drvdata(dai);
> +
> + bcm2708_i2s_stop(dev, substream);
> +
> + if (dev->first_stream == substream)
> + dev->first_stream = dev->second_stream;
> +
> + dev->second_stream = NULL;
> +
> + /* If both streams are stopped, disable module and clock */
> + if (!dev->first_stream) {
> + /* Disable the module */
> + bcm2708_i2s_clear_bits(dev, BCM2708_I2S_CS_A_REG,
> + BCM2708_I2S_EN);
> +
> + /*
> + * Stopping clock is necessary, because stop does
> + * not stop the clock when SND_SOC_DAIFMT_CONT
> + */
> + bcm2708_i2s_stop_clock(dev);
> + }
> +}
[...]
> diff --git a/sound/soc/bcm2708/bcm2708-pcm.c b/sound/soc/bcm2708/bcm2708-pcm.c
> new file mode 100644
> index 0000000..4b3e688
> --- /dev/null
> +++ b/sound/soc/bcm2708/bcm2708-pcm.c
> @@ -0,0 +1,303 @@
I think you should be able to remove the bulk of this driver by using the
generic PCM dmaengine driver.
[...]
> +
> +#include "bcm2708-pcm.h"
> +
> +static const struct snd_pcm_hardware bcm2708_pcm_hardware = {
> + .info = SNDRV_PCM_INFO_MMAP |
> + SNDRV_PCM_INFO_MMAP_VALID |
> + SNDRV_PCM_INFO_INTERLEAVED |
> + SNDRV_PCM_INFO_PAUSE |
> + SNDRV_PCM_INFO_RESUME |
> + SNDRV_PCM_INFO_JOINT_DUPLEX |
> + SNDRV_PCM_INFO_NO_PERIOD_WAKEUP,
I don't think you actually support the last one, and neither pause and
resume are supported.
> + .formats = SNDRV_PCM_FMTBIT_S16_LE |
> + SNDRV_PCM_FMTBIT_S32_LE,
> + .period_bytes_min = 32,
> + .period_bytes_max = 64 * 1024,
> + .periods_min = 2,
> + .periods_max = 255,
> + .buffer_bytes_max = 128 * 1024,
> +};
> +
[...]
--
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