mISDN: Add feature via MISDN_CTRL_FILL_EMPTY to fill fifo if empty

This prevents underrun of fifo when filled and in case of an underrun it
prevents subsequent underruns due to jitter.
Improve dsp, so buffers are kept filled with a certain delay, so moderate
jitter will not cause underrun all the time -> the audio quality is highly
improved. tones are not interrupted by gaps anymore, except when CPU is
stalling or in high load.

Signed-off-by: Andreas Eversberg <andreas@eversberg.eu>
Signed-off-by: Karsten Keil <kkeil@suse.de>

1 files changed, 37 insertions, 19 deletions

diff --git a/drivers/isdn/mISDN/dsp_cmx.c b/drivers/isdn/mISDN/dsp_cmx.c
index c884511e2d49..fc8ea41ae6a2 100644
--- a/drivers/isdn/mISDN/dsp_cmx.c
+++ b/drivers/isdn/mISDN/dsp_cmx.c
@@ -1168,11 +1168,18 @@ dsp_cmx_receive(struct dsp *dsp, struct sk_buff *skb)
 		dsp->rx_init = 0;
 		if (dsp->features.unordered) {
 			dsp->rx_R = (hh->id & CMX_BUFF_MASK);
-			dsp->rx_W = (dsp->rx_R + dsp->cmx_delay)
-				& CMX_BUFF_MASK;
+			if (dsp->cmx_delay)
+				dsp->rx_W = (dsp->rx_R + dsp->cmx_delay)
+					& CMX_BUFF_MASK;
+			else
+				dsp->rx_W = (dsp->rx_R + (dsp_poll >> 1))
+					& CMX_BUFF_MASK;
 		} else {
 			dsp->rx_R = 0;
-			dsp->rx_W = dsp->cmx_delay;
+			if (dsp->cmx_delay)
+				dsp->rx_W = dsp->cmx_delay;
+			else
+				dsp->rx_W = dsp_poll >> 1;
 		}
 	}
 	/* if frame contains time code, write directly */
@@ -1190,14 +1197,20 @@ dsp_cmx_receive(struct dsp *dsp, struct sk_buff *skb)
 			    "cmx_receive(dsp=%lx): UNDERRUN (or overrun the "
 			    "maximum delay), adjusting read pointer! "
 			    "(inst %s)\n", (u_long)dsp, dsp->name);
-		/* flush buffer */
+		/* flush rx buffer and set delay to dsp_poll / 2 */
 		if (dsp->features.unordered) {
 			dsp->rx_R = (hh->id & CMX_BUFF_MASK);
-			dsp->rx_W = (dsp->rx_R + dsp->cmx_delay)
-				& CMX_BUFF_MASK;
+			if (dsp->cmx_delay)
+				dsp->rx_W = (dsp->rx_R + dsp->cmx_delay)
+					& CMX_BUFF_MASK;
+				dsp->rx_W = (dsp->rx_R + (dsp_poll >> 1))
+					& CMX_BUFF_MASK;
 		} else {
 			dsp->rx_R = 0;
-			dsp->rx_W = dsp->cmx_delay;
+			if (dsp->cmx_delay)
+				dsp->rx_W = dsp->cmx_delay;
+			else
+				dsp->rx_W = dsp_poll >> 1;
 		}
 		memset(dsp->rx_buff, dsp_silence, sizeof(dsp->rx_buff));
 	}
@@ -1360,8 +1373,11 @@ dsp_cmx_send_member(struct dsp *dsp, int len, s32 *c, int members)
 				t = (t+1) & CMX_BUFF_MASK;
 				r = (r+1) & CMX_BUFF_MASK;
 			}
-			if (r != rr)
+			if (r != rr) {
+				printk(KERN_DEBUG "%s: buffer empty\n",
+					__func__);
 				memset(d, dsp_silence, (rr-r)&CMX_BUFF_MASK);
+			}
 		/* -> if echo is enabled */
 		} else {
 			/*
@@ -1704,9 +1720,10 @@ dsp_cmx_send(void *arg)
 			}
 			/*
 			 * remove rx_delay only if we have delay AND we
-			 * have not preset cmx_delay
+			 * have not preset cmx_delay AND
+			 * the delay is greater dsp_poll
 			 */
-			if (delay && !dsp->cmx_delay) {
+			if (delay > dsp_poll && !dsp->cmx_delay) {
 				if (dsp_debug & DEBUG_DSP_CMX)
 					printk(KERN_DEBUG
 					    "%s lowest rx_delay of %d bytes for"
@@ -1714,7 +1731,8 @@ dsp_cmx_send(void *arg)
 					    __func__, delay,
 					    dsp->name);
 				r = dsp->rx_R;
-				rr = (r + delay) & CMX_BUFF_MASK;
+				rr = (r + delay - (dsp_poll >> 1))
+					& CMX_BUFF_MASK;
 				/* delete rx-data */
 				while (r != rr) {
 					p[r] = dsp_silence;
@@ -1736,7 +1754,7 @@ dsp_cmx_send(void *arg)
 			 * remove delay only if we have delay AND we
 			 * have enabled tx_dejitter
 			 */
-			if (delay && dsp->tx_dejitter) {
+			if (delay > dsp_poll && dsp->tx_dejitter) {
 				if (dsp_debug & DEBUG_DSP_CMX)
 					printk(KERN_DEBUG
 					    "%s lowest tx_delay of %d bytes for"
@@ -1744,7 +1762,8 @@ dsp_cmx_send(void *arg)
 					    __func__, delay,
 					    dsp->name);
 				r = dsp->tx_R;
-				rr = (r + delay) & CMX_BUFF_MASK;
+				rr = (r + delay - (dsp_poll >> 1))
+					& CMX_BUFF_MASK;
 				/* delete tx-data */
 				while (r != rr) {
 					q[r] = dsp_silence;
@@ -1797,14 +1816,13 @@ dsp_cmx_transmit(struct dsp *dsp, struct sk_buff *skb)
 	ww = dsp->tx_R;
 	p = dsp->tx_buff;
 	d = skb->data;
-	space = ww-w;
-	if (space <= 0)
-		space += CMX_BUFF_SIZE;
+	space = (ww - w - 1) & CMX_BUFF_MASK;
 	/* write-pointer should not overrun nor reach read pointer */
-	if (space-1 < skb->len)
+	if (space < skb->len) {
 		/* write to the space we have left */
-		ww = (ww - 1) & CMX_BUFF_MASK;
-	else
+		ww = (ww - 1) & CMX_BUFF_MASK; /* end one byte prior tx_R */
+		printk(KERN_DEBUG "%s: buffer overflow\n", __func__);
+	} else
 		/* write until all byte are copied */
 		ww = (w + skb->len) & CMX_BUFF_MASK;
 	dsp->tx_W = ww;