[Sound-open-firmware] [PATCH] [RFC]SOF: FIX: adjust the SSC3's TFT/RFT field in SSP

[Wu Zhigang]

Actually I did not have full confidence about this patch.
if someone can help do more test, that would be better.
before this, do not accept this patch.

Incorrect TFT/RFT will cause DMA IRQ happened too frequently.
the interval will be less than 1ms, which will cause XRUN easily.

The old code will has this issue in TDM4-s32le test.

Signed-off-by: Wu Zhigang <zhigang.wu at linux.intel.com>
Acked-by: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>

---
Test with:
APL-GPMRB with TDF8532 codec
Linux sof-v4.14: 1d4a25d72d1e87c182f15a68d32c9599b734ea7b
SOF master: 7c5dd8cfdf4f8ca1fa5cfdd7352b81cbfc8edb88
Tools master: 86fe688a2b4f68a1ce87e0951686be12a00f1a3c

Pass the Sanity test:
BYT(Minnowboard Turbo)
APL(UP^2)
CNL(CNL-RVP)
---
 src/drivers/apl-ssp.c | 21 +++------------------
 1 file changed, 3 insertions(+), 18 deletions(-)

diff --git a/src/drivers/apl-ssp.c b/src/drivers/apl-ssp.c
index a51f91c..5fb9b27 100644
--- a/src/drivers/apl-ssp.c
+++ b/src/drivers/apl-ssp.c
@@ -36,6 +36,7 @@
 #include <sof/ssp.h>
 #include <sof/alloc.h>
 #include <sof/interrupt.h>
+#include <sof/math/numbers.h>
 #include <config.h>
 
 /* tracing */
@@ -496,24 +497,8 @@ static inline int ssp_set_config(struct dai *dai,
 	/* bypass divider for MCLK */
 	mdivr = 0x00000fff;
 
-	/* setting TFT and RFT */
-	switch (config->ssp.sample_valid_bits) {
-	case 16:
-		/* use 2 bytes for each slot */
-		tft = active_tx_slots * 2;
-		rft = active_rx_slots * 2;
-		break;
-	case 24:
-	case 32:
-		/* use 4 bytes for each slot */
-		tft = active_tx_slots * 4;
-		rft = active_rx_slots * 4;
-		break;
-	default:
-		trace_ssp_error("ecd");
-		ret = -EINVAL;
-		goto out;
-	}
+	tft = MIN(8, 2 * active_tx_slots);
+	rft = MIN(8, 2 * active_rx_slots);
 
 	sscr3 |= SSCR3_TX(tft) | SSCR3_RX(rft);
 
-- 
2.14.1