linux-kernel - Re: [PATCH V4 4/9] ASoC: amd: ps: add SoundWire dma driver dma ops

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Date:   Mon, 12 Jun 2023 13:06:19 -0500
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Vijendar Mukunda <Vijendar.Mukunda@....com>, broonie@...nel.org
Cc:     alsa-devel@...a-project.org, Basavaraj.Hiregoudar@....com,
        Sunil-kumar.Dommati@....com, Mastan.Katragadda@....com,
        Arungopal.kondaveeti@....com, mario.limonciello@....com,
        Liam Girdwood <lgirdwood@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Syed Saba Kareem <Syed.SabaKareem@....com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V4 4/9] ASoC: amd: ps: add SoundWire dma driver dma ops


> +#define SDW_PLAYBACK_MIN_NUM_PERIODS    2
> +#define SDW_PLAYBACK_MAX_NUM_PERIODS    8
> +#define SDW_PLAYBACK_MAX_PERIOD_SIZE    8192

that's a fairly small max period. That's 21ms for 2ch S32_LE 48kHz.

Does this come from specific limitations or is this an arbitrary number?

A comment on this wouldn't hurt.

> +static u32 sdw0_dma_enable_reg[ACP63_SDW0_DMA_MAX_STREAMS] = {
> +	ACP_SW0_AUDIO0_TX_EN,
> +	ACP_SW0_AUDIO1_TX_EN,
> +	ACP_SW0_AUDIO2_TX_EN,
> +	ACP_SW0_AUDIO0_RX_EN,
> +	ACP_SW0_AUDIO1_RX_EN,
> +	ACP_SW0_AUDIO2_RX_EN,
> +};
> +
> +static u32 sdw1_dma_enable_reg[ACP63_SDW1_DMA_MAX_STREAMS] = {
> +	ACP_SW1_AUDIO1_TX_EN,
> +	ACP_SW1_AUDIO1_RX_EN,
> +};

Still no explanation as to why SDW0 indices start at zero and SDW1
indices start at one?

> +
> +static const struct snd_pcm_hardware acp63_sdw_hardware_playback = {
> +	.info = SNDRV_PCM_INFO_INTERLEAVED |
> +		SNDRV_PCM_INFO_BLOCK_TRANSFER |
> +		SNDRV_PCM_INFO_MMAP | SNDRV_PCM_INFO_MMAP_VALID |
> +		SNDRV_PCM_INFO_PAUSE | SNDRV_PCM_INFO_RESUME,
> +	.formats = SNDRV_PCM_FMTBIT_S16_LE |  SNDRV_PCM_FMTBIT_S8 |
> +		   SNDRV_PCM_FMTBIT_U8 | SNDRV_PCM_FMTBIT_S24_LE | SNDRV_PCM_FMTBIT_S32_LE,
> +	.channels_min = 2,
> +	.channels_max = 2,
> +	.rates = SNDRV_PCM_RATE_48000,
> +	.rate_min = 48000,
> +	.rate_max = 48000,
> +	.buffer_bytes_max = SDW_PLAYBACK_MAX_NUM_PERIODS * SDW_PLAYBACK_MAX_PERIOD_SIZE,
> +	.period_bytes_min = SDW_PLAYBACK_MIN_PERIOD_SIZE,
> +	.period_bytes_max = SDW_PLAYBACK_MAX_PERIOD_SIZE,
> +	.periods_min = SDW_PLAYBACK_MIN_NUM_PERIODS,
> +	.periods_max = SDW_PLAYBACK_MAX_NUM_PERIODS,
> +};
> +
> +static const struct snd_pcm_hardware acp63_sdw_hardware_capture = {
> +	.info = SNDRV_PCM_INFO_INTERLEAVED |
> +		SNDRV_PCM_INFO_BLOCK_TRANSFER |
> +		SNDRV_PCM_INFO_MMAP |
> +		SNDRV_PCM_INFO_MMAP_VALID |
> +		SNDRV_PCM_INFO_PAUSE | SNDRV_PCM_INFO_RESUME,
> +	.formats = SNDRV_PCM_FMTBIT_S16_LE |  SNDRV_PCM_FMTBIT_S8 |
> +		   SNDRV_PCM_FMTBIT_U8 | SNDRV_PCM_FMTBIT_S24_LE | SNDRV_PCM_FMTBIT_S32_LE,
> +	.channels_min = 2,
> +	.channels_max = 2,
> +	.rates = SNDRV_PCM_RATE_48000,
> +	.rate_min = 48000,
> +	.rate_max = 48000,
> +	.buffer_bytes_max = SDW_CAPTURE_MAX_NUM_PERIODS * SDW_CAPTURE_MAX_PERIOD_SIZE,
> +	.period_bytes_min = SDW_CAPTURE_MIN_PERIOD_SIZE,
> +	.period_bytes_max = SDW_CAPTURE_MAX_PERIOD_SIZE,
> +	.periods_min = SDW_CAPTURE_MIN_NUM_PERIODS,
> +	.periods_max = SDW_CAPTURE_MAX_NUM_PERIODS,
> +};

> +static int acp63_sdw_dma_open(struct snd_soc_component *component,
> +			      struct snd_pcm_substream *substream)
> +{
> +	struct snd_pcm_runtime *runtime;
> +	struct acp_sdw_dma_stream *stream;
> +	struct snd_soc_dai *cpu_dai;
> +	struct amd_sdw_manager *amd_manager;
> +	struct snd_soc_pcm_runtime *prtd = substream->private_data;
> +	int ret;
> +
> +	runtime = substream->runtime;
> +	cpu_dai = asoc_rtd_to_cpu(prtd, 0);
> +	amd_manager = snd_soc_dai_get_drvdata(cpu_dai);
> +	stream = kzalloc(sizeof(*stream), GFP_KERNEL);
> +	if (!stream)
> +		return -ENOMEM;
> +
> +	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
> +		runtime->hw = acp63_sdw_hardware_playback;
> +	else
> +		runtime->hw = acp63_sdw_hardware_capture;
> +	ret = snd_pcm_hw_constraint_integer(runtime,
> +					    SNDRV_PCM_HW_PARAM_PERIODS);
> +	if (ret < 0) {
> +		dev_err(component->dev, "set integer constraint failed\n");
> +		kfree(stream);
> +		return ret;
> +	}

it's not clear to me why you have to add this specific constraint, isn't
this checked already with the sdw_hardware_playback information.

> +static u64 acp63_sdw_get_byte_count(struct acp_sdw_dma_stream *stream, void __iomem *acp_base)
> +{
> +	union acp_sdw_dma_count byte_count;
> +	u32 pos_low_reg, pos_high_reg;
> +
> +	byte_count.bytescount = 0;
> +	switch (stream->instance) {
> +	case ACP_SDW0:
> +		pos_low_reg = sdw0_dma_ring_buf_reg[stream->stream_id].pos_low_reg;
> +		pos_high_reg = sdw0_dma_ring_buf_reg[stream->stream_id].pos_high_reg;
> +		break;
> +	case ACP_SDW1:
> +		pos_low_reg = sdw1_dma_ring_buf_reg[stream->stream_id].pos_low_reg;
> +		pos_high_reg = sdw1_dma_ring_buf_reg[stream->stream_id].pos_high_reg;
> +		break;
> +	default:
> +		return -EINVAL;

returning -EINVAL as a u64 doesn't seem quite right to me?

> +	}
> +	if (pos_low_reg) {
> +		byte_count.bcount.high = readl(acp_base + pos_high_reg);
> +		byte_count.bcount.low = readl(acp_base + pos_low_reg);
> +	}
> +	return byte_count.bytescount;
> +}