linux-kernel - Re: [PATCH V2 5/9] ASoC: amd: ps: add support for SoundWire DMA interrupts

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Date:   Mon, 22 May 2023 13:12:06 -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 V2 5/9] ASoC: amd: ps: add support for SoundWire DMA
 interrupts



On 5/22/23 08:31, Vijendar Mukunda wrote:
> Initialize workqueue for SoundWire DMA interrupts handling.
> Whenever audio data equal to the SoundWire FIFO watermark level
> are produced/consumed, interrupt is generated.
> Acknowledge the interrupt and schedule the workqueue.

It would help to explain why a work queue is needed is the first place,
as opposed to handling periods in the interrupt thread.

> +static void acp63_sdw_dma_workthread(struct work_struct *work)
> +{
> +	struct acp63_dev_data *adata = container_of(work, struct acp63_dev_data,
> +						    acp_sdw_dma_work);
> +	struct sdw_dma_dev_data *sdw_dma_data;
> +	u32 stream_index;
> +	u16 pdev_index;
> +
> +	pdev_index = adata->sdw_dma_dev_index;
> +	sdw_dma_data = dev_get_drvdata(&adata->pdev[pdev_index]->dev);
> +
> +	for (stream_index = 0; stream_index < ACP63_SDW0_DMA_MAX_STREAMS; stream_index++) {
> +		if (adata->sdw0_dma_intr_stat[stream_index]) {
> +			if (sdw_dma_data->sdw0_dma_stream[stream_index])
> +				snd_pcm_period_elapsed(sdw_dma_data->sdw0_dma_stream[stream_index]);
> +			adata->sdw0_dma_intr_stat[stream_index] = 0;
> +		}
> +	}
> +	for (stream_index = 0; stream_index < ACP63_SDW1_DMA_MAX_STREAMS; stream_index++) {
> +		if (adata->sdw1_dma_intr_stat[stream_index]) {
> +			if (sdw_dma_data->sdw1_dma_stream[stream_index])
> +				snd_pcm_period_elapsed(sdw_dma_data->sdw1_dma_stream[stream_index]);
> +			adata->sdw1_dma_intr_stat[stream_index] = 0;
> +		}
> +	}

I am not clear on the benefits of the workqueue which only tests a flag
that's set ...

> +}
> +
>  static irqreturn_t acp63_irq_handler(int irq, void *dev_id)
>  {
>  	struct acp63_dev_data *adata;
>  	struct pdm_dev_data *ps_pdm_data;
>  	struct amd_sdw_manager *amd_manager;
>  	u32 ext_intr_stat, ext_intr_stat1;
> +	u32 stream_id = 0;
>  	u16 irq_flag = 0;
> +	u16 sdw_dma_irq_flag = 0;
>  	u16 pdev_index;
> +	u16 index;
>  
>  	adata = dev_id;
>  	if (!adata)
> @@ -148,7 +178,57 @@ static irqreturn_t acp63_irq_handler(int irq, void *dev_id)
>  			snd_pcm_period_elapsed(ps_pdm_data->capture_stream);
>  		irq_flag = 1;
>  	}
> -	if (irq_flag)
> +	if (ext_intr_stat & ACP_SDW_DMA_IRQ_MASK) {
> +		for (index = ACP_AUDIO2_RX_THRESHOLD; index <= ACP_AUDIO0_TX_THRESHOLD; index++) {
> +			if (ext_intr_stat & BIT(index)) {
> +				writel(BIT(index), adata->acp63_base + ACP_EXTERNAL_INTR_STAT);
> +				switch (index) {
> +				case ACP_AUDIO0_TX_THRESHOLD:
> +					stream_id = ACP_SDW0_AUDIO0_TX;
> +					break;
> +				case ACP_AUDIO1_TX_THRESHOLD:
> +					stream_id = ACP_SDW0_AUDIO1_TX;
> +					break;
> +				case ACP_AUDIO2_TX_THRESHOLD:
> +					stream_id = ACP_SDW0_AUDIO2_TX;
> +					break;
> +				case ACP_AUDIO0_RX_THRESHOLD:
> +					stream_id = ACP_SDW0_AUDIO0_RX;
> +					break;
> +				case ACP_AUDIO1_RX_THRESHOLD:
> +					stream_id = ACP_SDW0_AUDIO1_RX;
> +					break;
> +				case ACP_AUDIO2_RX_THRESHOLD:
> +					stream_id = ACP_SDW0_AUDIO2_RX;
> +					break;
> +				}
> +
> +				adata->sdw0_dma_intr_stat[stream_id] = 1;

.. here ...
> +				sdw_dma_irq_flag = 1;
> +			}
> +		}
> +	}
> +
> +	/* SDW1 BT RX */
> +	if (ext_intr_stat1 & ACP_P1_AUDIO1_RX_THRESHOLD) {
> +		writel(ACP_P1_AUDIO1_RX_THRESHOLD,
> +		       adata->acp63_base + ACP_EXTERNAL_INTR_STAT1);
> +		adata->sdw1_dma_intr_stat[ACP_SDW1_AUDIO1_RX] = 1;

... and here ...

> +		sdw_dma_irq_flag = 1;
> +	}
> +
> +	/* SDW1 BT TX*/
> +	if (ext_intr_stat1 & ACP_P1_AUDIO1_TX_THRESHOLD) {
> +		writel(ACP_P1_AUDIO1_TX_THRESHOLD,
> +		       adata->acp63_base + ACP_EXTERNAL_INTR_STAT1);
> +		adata->sdw1_dma_intr_stat[ACP_SDW1_AUDIO1_TX] = 1;

... or here ...

> +		sdw_dma_irq_flag = 1;
> +	}
> +
> +	if (sdw_dma_irq_flag)
> +		schedule_work(&adata->acp_sdw_dma_work);
> +
> +	if (irq_flag || sdw_dma_irq_flag)
>  		return IRQ_HANDLED;
>  	else
>  		return IRQ_NONE;