ASoC: dwc: Unmask I2S interrupts only for enabled channels

There is no need to unmask all interrupts at I2S start. This
can cause performance issues in slower platforms.

Unmask only the interrupts for the used channels.
Signed-off-by: NJose Abreu <joabreu@synopsys.com>
Signed-off-by: NMark Brown <broonie@kernel.org>

sound/soc/dwc/designware_i2s.c

@@ -147,17 +147,18 @@ static inline void i2s_clear_irqs(struct dw_i2s_dev *dev, u32 stream)
 static void i2s_start(struct dw_i2s_dev *dev,
 		      struct snd_pcm_substream *substream)
 {
+	struct i2s_clk_config_data *config = &dev->config;
 	u32 i, irq;
 	i2s_write_reg(dev->i2s_base, IER, 1);
 
 	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
-		for (i = 0; i < 4; i++) {
+		for (i = 0; i < (config->chan_nr / 2); i++) {
 			irq = i2s_read_reg(dev->i2s_base, IMR(i));
 			i2s_write_reg(dev->i2s_base, IMR(i), irq & ~0x30);
 		}
 		i2s_write_reg(dev->i2s_base, ITER, 1);
 	} else {
-		for (i = 0; i < 4; i++) {
+		for (i = 0; i < (config->chan_nr / 2); i++) {
 			irq = i2s_read_reg(dev->i2s_base, IMR(i));
 			i2s_write_reg(dev->i2s_base, IMR(i), irq & ~0x03);
 		}