byt:ssp:porting the patch dcc6149 to clear fifo.

porting the patch dcc6149 on byt platform,
to clear out the stale samples in ssp's FIFO.

Signed-off-by: Wu Zhigang <zhigang.wu@linux.intel.com>

Author: Wu Zhigang

src/drivers/byt-ssp.c

@@ -54,6 +54,32 @@ static int hweight_32(uint32_t mask)
 	return count;
 }
 
+/* empty SSP receive FIFO */
+static void ssp_empty_rx_fifo(struct dai *dai)
+{
+	struct ssp_pdata *ssp = dai_get_drvdata(dai);
+	uint32_t sssr;
+	uint32_t entries;
+	uint32_t i;
+
+	spin_lock(&ssp->lock);
+
+	sssr = ssp_read(dai, SSSR);
+
+	/* clear interrupt */
+	if (sssr & SSSR_ROR)
+		ssp_write(dai, SSSR, sssr);
+
+	/* empty fifo */
+	if (sssr & SSSR_RNE) {
+		entries = SFIFOL_RFL(ssp_read(dai, SFIFOL));
+		for (i = 0; i < entries + 1; i++)
+			ssp_read(dai, SSDR);
+	}
+
+	spin_unlock(&ssp->lock);
+}
+
 /* save SSP context prior to entering D3 */
 static int ssp_context_store(struct dai *dai)
 {
@@ -500,6 +526,7 @@ static void ssp_stop(struct dai *dai, int direction)
 	if (direction == DAI_DIR_CAPTURE &&
 	    ssp->state[SOF_IPC_STREAM_CAPTURE] == COMP_STATE_ACTIVE) {
 		ssp_update_bits(dai, SSCR1, SSCR1_RSRE, 0);
+		ssp_empty_rx_fifo(dai);
 		ssp->state[SOF_IPC_STREAM_CAPTURE] = COMP_STATE_PAUSED;
 		trace_ssp("Ss0");
 	}
@@ -598,6 +625,7 @@ static int ssp_probe(struct dai *dai)
 	platform_interrupt_unmask(ssp_irq(dai), 1);
 	interrupt_enable(ssp_irq(dai));
 
+	ssp_empty_rx_fifo(dai);
 	return 0;
 }
 

src/include/sof/ssp.h

@@ -61,6 +61,7 @@
 	defined CONFIG_CHERRYTRAIL ||\
 	defined CONFIG_BROADWELL ||\
 	defined CONFIG_HASWELL
+#define SFIFOL		0x68
 #define SFIFOTT		0x6C
 #define SSCR3		0x70
 #define SSCR4		0x74
@@ -198,6 +199,10 @@ extern const struct dai_ops ssp_ops;
 #define SFIFOTT_TX(x)		((x) - 1)
 #define SFIFOTT_RX(x)		(((x) - 1) << 16)
 
+/* SFIFOL bits */
+#define SFIFOL_TFL(x)		((x) & 0xFFFF)
+#define SFIFOL_RFL(x)		((x) >> 16)
+
 #if defined CONFIG_APOLLOLAKE || defined CONFIG_CANNONLAKE ||\
 	defined CONFIG_HASWELL || defined CONFIG_BROADWELL
 #define SSTSA_TSEN			BIT(8)