Unverified Commit a2dc6f82 authored by Peter Ujfalusi's avatar Peter Ujfalusi Committed by Mark Brown
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ASoC: ti: davinci-i2s: Move the XSYNCERR workaround to .prepare callback 



Currently the driver uses snd_soc_rtdcom_lookup() in it's mcbsp_start
function to try to stop/restart the DMA as the initial XSYNCERR workaround
need to be done before the DMA is armed.

There are couple of things wrong with this:
- the driver crashes with NULL pointer dereference as the
  component->driver->ops is actually NULL
- the driver should not use snd_soc_rtdcom_lookup() in the first place
- Fiddling with DMA is never a good thing

Move the workaround handling to .prepare which is called before the DMA is
armed, so it complies with the requirements.

Reported-by (usage of snd_soc_rtdcom_lookup): Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: default avatarPeter Ujfalusi <peter.ujfalusi@ti.com>
Link: https://lore.kernel.org/r/20190830103841.25128-3-peter.ujfalusi@ti.com


Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent cc9bbb6c

sound/soc/ti/davinci-i2s.c

+34 −48
Original line number Diff line number Diff line
@@ -187,57 +187,9 @@ static void toggle_clock(struct davinci_mcbsp_dev *dev, int playback) 
static void davinci_mcbsp_start(struct davinci_mcbsp_dev *dev,

		struct snd_pcm_substream *substream)

{

	struct snd_soc_pcm_runtime *rtd = substream->private_data;

	struct snd_soc_component *component = snd_soc_rtdcom_lookup(rtd, DRV_NAME);

	int playback = (substream->stream == SNDRV_PCM_STREAM_PLAYBACK);

	u32 spcr;

	u32 mask = playback ? DAVINCI_MCBSP_SPCR_XRST : DAVINCI_MCBSP_SPCR_RRST;

	spcr = davinci_mcbsp_read_reg(dev, DAVINCI_MCBSP_SPCR_REG);

	if (spcr & mask) {

		/* start off disabled */

		davinci_mcbsp_write_reg(dev, DAVINCI_MCBSP_SPCR_REG,

				spcr & ~mask);

		toggle_clock(dev, playback);

	}

	if (dev->pcr & (DAVINCI_MCBSP_PCR_FSXM | DAVINCI_MCBSP_PCR_FSRM |

			DAVINCI_MCBSP_PCR_CLKXM | DAVINCI_MCBSP_PCR_CLKRM)) {

		/* Start the sample generator */

		spcr |= DAVINCI_MCBSP_SPCR_GRST;

		davinci_mcbsp_write_reg(dev, DAVINCI_MCBSP_SPCR_REG, spcr);

	}



	if (playback) {

		/* Stop the DMA to avoid data loss */

		/* while the transmitter is out of reset to handle XSYNCERR */

		if (component->driver->ops->trigger) {

			int ret = component->driver->ops->trigger(substream,

				SNDRV_PCM_TRIGGER_STOP);

			if (ret < 0)

				printk(KERN_DEBUG "Playback DMA stop failed\n");

		}



		/* Enable the transmitter */

		spcr = davinci_mcbsp_read_reg(dev, DAVINCI_MCBSP_SPCR_REG);

		spcr |= DAVINCI_MCBSP_SPCR_XRST;

		davinci_mcbsp_write_reg(dev, DAVINCI_MCBSP_SPCR_REG, spcr);



		/* wait for any unexpected frame sync error to occur */

		udelay(100);



		/* Disable the transmitter to clear any outstanding XSYNCERR */

		spcr = davinci_mcbsp_read_reg(dev, DAVINCI_MCBSP_SPCR_REG);

		spcr &= ~DAVINCI_MCBSP_SPCR_XRST;

		davinci_mcbsp_write_reg(dev, DAVINCI_MCBSP_SPCR_REG, spcr);

		toggle_clock(dev, playback);



		/* Restart the DMA */

		if (component->driver->ops->trigger) {

			int ret = component->driver->ops->trigger(substream,

				SNDRV_PCM_TRIGGER_START);

			if (ret < 0)

				printk(KERN_DEBUG "Playback DMA start failed\n");

		}

	}



	/* Enable transmitter or receiver */

	spcr = davinci_mcbsp_read_reg(dev, DAVINCI_MCBSP_SPCR_REG);
@@ -575,7 +527,41 @@ static int davinci_i2s_prepare(struct snd_pcm_substream *substream, 
{

	struct davinci_mcbsp_dev *dev = snd_soc_dai_get_drvdata(dai);

	int playback = (substream->stream == SNDRV_PCM_STREAM_PLAYBACK);

	u32 spcr;

	u32 mask = playback ? DAVINCI_MCBSP_SPCR_XRST : DAVINCI_MCBSP_SPCR_RRST;



	davinci_mcbsp_stop(dev, playback);



	spcr = davinci_mcbsp_read_reg(dev, DAVINCI_MCBSP_SPCR_REG);

	if (spcr & mask) {

		/* start off disabled */

		davinci_mcbsp_write_reg(dev, DAVINCI_MCBSP_SPCR_REG,

					spcr & ~mask);

		toggle_clock(dev, playback);

	}

	if (dev->pcr & (DAVINCI_MCBSP_PCR_FSXM | DAVINCI_MCBSP_PCR_FSRM |

			DAVINCI_MCBSP_PCR_CLKXM | DAVINCI_MCBSP_PCR_CLKRM)) {

		/* Start the sample generator */

		spcr |= DAVINCI_MCBSP_SPCR_GRST;

		davinci_mcbsp_write_reg(dev, DAVINCI_MCBSP_SPCR_REG, spcr);

	}



	if (playback) {

		/* Enable the transmitter */

		spcr = davinci_mcbsp_read_reg(dev, DAVINCI_MCBSP_SPCR_REG);

		spcr |= DAVINCI_MCBSP_SPCR_XRST;

		davinci_mcbsp_write_reg(dev, DAVINCI_MCBSP_SPCR_REG, spcr);



		/* wait for any unexpected frame sync error to occur */

		udelay(100);



		/* Disable the transmitter to clear any outstanding XSYNCERR */

		spcr = davinci_mcbsp_read_reg(dev, DAVINCI_MCBSP_SPCR_REG);

		spcr &= ~DAVINCI_MCBSP_SPCR_XRST;

		davinci_mcbsp_write_reg(dev, DAVINCI_MCBSP_SPCR_REG, spcr);

		toggle_clock(dev, playback);

	}



	return 0;

}

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