Subject: Re: [PATCH 3/3] ASoC: fsl_asrc: Fix error with S24_3LE format bitstream in i.MX8

From: Nicolin Chen <[email-masked]>
Date: Mon, 9 Sep 2019 18:52:13 -0700

On Mon, Sep 09, 2019 at 06:33:21PM -0400, Shengjiu Wang wrote:
> There is error "aplay: pcm_write:2023: write error: Input/output error"
> on i.MX8QM/i.MX8QXP platform for S24_3LE format.
> 
> In i.MX8QM/i.MX8QXP, the DMA is EDMA, which don't support 24bit
> sample, but we didn't add any constraint, that cause issues.
> 
> So we need to query the caps of dma, then update the hw parameters
> according to the caps.

> @@ -285,8 +293,81 @@ static int fsl_asrc_dma_startup(struct snd_pcm_substream *substream)
>  
>  	runtime->private_data = pair;
>  
> -	snd_pcm_hw_constraint_integer(substream->runtime,
> -				      SNDRV_PCM_HW_PARAM_PERIODS);
> +	ret = snd_pcm_hw_constraint_integer(substream->runtime,
> +					    SNDRV_PCM_HW_PARAM_PERIODS);
> +	if (ret < 0) {
> +		dev_err(dev, "failed to set pcm hw params periods\n");
> +		return ret;
> +	}
> +
> +	dma_data = snd_soc_dai_get_dma_data(rtd->cpu_dai, substream);
> +
> +	/* Request a temp pair, which is release in the end */
> +	fsl_asrc_request_pair(1, pair);

Not sure if it'd be practical, but a pair request could fail. Will
probably need to check return value.

And a quick feeling is that below code is mostly identical to what
is in the soc-generic-dmaengine-pcm.c file. So I'm wondering if we
could abstract a helper function somewhere in the ASoC core: Mark?

Thanks
Nicolin

> +	tmp_chan = fsl_asrc_get_dma_channel(pair, dir);
> +	if (!tmp_chan) {
> +		dev_err(dev, "can't get dma channel\n");
> +		return -EINVAL;
> +	}
> +
> +	ret = dma_get_slave_caps(tmp_chan, &dma_caps);
> +	if (ret == 0) {
> +		if (dma_caps.cmd_pause)
> +			snd_imx_hardware.info |= SNDRV_PCM_INFO_PAUSE |
> +						 SNDRV_PCM_INFO_RESUME;
> +		if (dma_caps.residue_granularity <=
> +			DMA_RESIDUE_GRANULARITY_SEGMENT)
> +			snd_imx_hardware.info |= SNDRV_PCM_INFO_BATCH;
> +
> +		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
> +			addr_widths = dma_caps.dst_addr_widths;
> +		else
> +			addr_widths = dma_caps.src_addr_widths;
> +	}
> +
> +	/*
> +	 * If SND_DMAENGINE_PCM_DAI_FLAG_PACK is set keep
> +	 * hw.formats set to 0, meaning no restrictions are in place.
> +	 * In this case it's the responsibility of the DAI driver to
> +	 * provide the supported format information.
> +	 */
> +	if (!(dma_data->flags & SND_DMAENGINE_PCM_DAI_FLAG_PACK))
> +		/*
> +		 * Prepare formats mask for valid/allowed sample types. If the
> +		 * dma does not have support for the given physical word size,
> +		 * it needs to be masked out so user space can not use the
> +		 * format which produces corrupted audio.
> +		 * In case the dma driver does not implement the slave_caps the
> +		 * default assumption is that it supports 1, 2 and 4 bytes
> +		 * widths.
> +		 */
> +		for (i = 0; i <= SNDRV_PCM_FORMAT_LAST; i++) {
> +			int bits = snd_pcm_format_physical_width(i);
> +
> +			/*
> +			 * Enable only samples with DMA supported physical
> +			 * widths
> +			 */
> +			switch (bits) {
> +			case 8:
> +			case 16:
> +			case 24:
> +			case 32:
> +			case 64:
> +				if (addr_widths & (1 << (bits / 8)))
> +					snd_imx_hardware.formats |= (1LL << i);
> +				break;
> +			default:
> +				/* Unsupported types */
> +				break;
> +			}
> +		}
> +
> +	if (tmp_chan)
> +		dma_release_channel(tmp_chan);
> +	fsl_asrc_release_pair(pair);
> +
>  	snd_soc_set_runtime_hwparams(substream, &snd_imx_hardware);
>  
>  	return 0;
> -- 
> 2.21.0
>