Re: [PATCH 2/2] ASoC: Intel: KMB: Enable DMA transfer mode

On 12/15/20 6:33 AM, Michael Sit Wei Hong wrote:

[...] +static inline void kmb_i2s_enable_dma(struct kmb_i2s_info *kmb_i2s, u32 stream) +{

• u32 dma_reg;
• dma_reg = readl(kmb_i2s->i2s_base + I2S_DMACR);
• /* Enable DMA handshake for stream */
• if (stream == SNDRV_PCM_STREAM_PLAYBACK)

• dma_reg |= I2S_DMAEN_TXBLOCK;
  

• else

• dma_reg |= I2S_DMAEN_RXBLOCK;
  

• writel(dma_reg, kmb_i2s->i2s_base + I2S_DMACR);

+}

+static inline void kmb_i2s_disable_dma(struct kmb_i2s_info *kmb_i2s, u32 stream) +{

• u32 dma_reg;
• dma_reg = readl(kmb_i2s->i2s_base + I2S_DMACR);
• /* Disable DMA handshake for stream */
• if (stream == SNDRV_PCM_STREAM_PLAYBACK) {

• dma_reg &= ~I2S_DMAEN_TXBLOCK;
  

• writel(1, kmb_i2s->i2s_base + I2S_RTXDMA);
  

• } else {

• dma_reg &= ~I2S_DMAEN_RXBLOCK;
  

• writel(1, kmb_i2s->i2s_base + I2S_RRXDMA);
  

• }
• writel(dma_reg, kmb_i2s->i2s_base + I2S_DMACR);

Does this need locking? I believe it is possible for the startup callback of the playback and capture stream to be called concurrently.

+}

• static void kmb_i2s_start(struct kmb_i2s_info *kmb_i2s, struct snd_pcm_substream *substream) {

@@ -356,7 +405,11 @@ static void kmb_i2s_start(struct kmb_i2s_info *kmb_i2s, else writel(1, kmb_i2s->i2s_base + IRER);

• kmb_i2s_irq_trigger(kmb_i2s, substream->stream, config->chan_nr, true);

• if (kmb_i2s->use_pio)

• kmb_i2s_irq_trigger(kmb_i2s, substream->stream,
  

• 		    config->chan_nr, true);
  

• else

• kmb_i2s_enable_dma(kmb_i2s, substream->stream);
  
  

  if (kmb_i2s->master) writel(1, kmb_i2s->i2s_base + CER);

[...]