Do not make assumptions about the number of ready HDLC frames on HDLC RX

interrupt.  This prevents libpri from becoming confused when many HDLC frames
arrive before the driver can service them or a false RX interrupt is received.

Patch provided by akolsmith. Issue DAHDI-173.


git-svn-id: http://svn.asterisk.org/svn/dahdi/linux/trunk@5367 a0bf4364-ded3-4de4-8d8a-66a801d63aff

1 files changed, 35 insertions, 14 deletions

diff --git a/drivers/dahdi/wcb4xxp/base.c b/drivers/dahdi/wcb4xxp/base.c
index 38e45ec..977127c 100644
--- a/drivers/dahdi/wcb4xxp/base.c
+++ b/drivers/dahdi/wcb4xxp/base.c
@@ -1522,32 +1522,44 @@ static void hdlc_stop(struct b4xxp *b4, int fifo)
 /*
  * Inner loop for D-channel receive function.
  * Retrieves a full HDLC frame from the hardware.
- * If the hardware indicates that the frame is complete, checks the FCS and updates
- * DAHDI as needed.
- * Returns 1 if an HDLC frame was correctly received, 0 otherwise.
+ * If the hardware indicates that the frame is complete,
+ * we check the HDLC engine's STAT byte and update DAHDI as needed.
+ *
+ * Returns the number of HDLC frames left in the FIFO.
  */
 static int hdlc_rx_frame(struct b4xxp_span *bspan)
 {
-	int fifo, i, j, zlen, zleft, z1, z2, ret;
-	unsigned char buf[32];		/* arbitrary */
+	int fifo, i, j, zleft;
+	int z1, z2, zlen, f1, f2, flen;
+	unsigned char buf[WCB4XXP_HDLC_BUF_LEN];
 	unsigned long irq_flags;
 	struct b4xxp *b4 = bspan->parent;
 
-	ret = 0;
 	fifo = bspan->fifos[2];
 	++bspan->frames_in;
 
 	spin_lock_irqsave(&b4->fifolock, irq_flags);
 	hfc_setreg_waitbusy(b4, R_FIFO, (fifo << V_FIFO_NUM_SHIFT) | V_FIFO_DIR);
+	get_F(f1, f2, flen);
 	get_Z(z1, z2, zlen);
 	spin_unlock_irqrestore(&b4->fifolock, irq_flags);
 
+/* first check to make sure we really do have HDLC frames available to retrieve */
+	if (flen == 0) {
+		if (DBG_HDLC) {
+			dev_info(b4->dev, "hdlc_rx_frame(span %d): no frames available?\n",
+				bspan->port + 1);
+		}
+
+		return flen;
+	}
+
 	zlen++;		/* include STAT byte that the HFC injects after FCS */
 	zleft = zlen;
 
 	do {
-		if (zleft > 32)
-			j = 32;
+		if (zleft > WCB4XXP_HDLC_BUF_LEN)
+			j = WCB4XXP_HDLC_BUF_LEN;
 		else
 			j = zleft;
 
@@ -1558,7 +1570,7 @@ static int hdlc_rx_frame(struct b4xxp_span *bspan)
 		spin_unlock_irqrestore(&b4->fifolock, irq_flags);
 
 /* don't send STAT byte to DAHDI */
-		dahdi_hdlc_putbuf(bspan->sigchan, buf, (j == 32) ? j : j - 1);
+		dahdi_hdlc_putbuf(bspan->sigchan, buf, (j == WCB4XXP_HDLC_BUF_LEN) ? j : j - 1);
 
 		zleft -= j;
 		if (DBG_HDLC) {
@@ -1568,8 +1580,10 @@ static int hdlc_rx_frame(struct b4xxp_span *bspan)
 		}
 	} while (zleft > 0);
 
+/* Frame received, increment F2 and get an updated count of frames left */
 	spin_lock_irqsave(&b4->fifolock, irq_flags);
 	hfc_setreg_waitbusy(b4, A_INC_RES_FIFO, V_INC_F);
+	get_F(f1, f2, flen);
 	spin_unlock_irqrestore(&b4->fifolock, irq_flags);
 
 	if (zlen < 3) {
@@ -1597,11 +1611,10 @@ static int hdlc_rx_frame(struct b4xxp_span *bspan)
 			if (DBG_HDLC)
 				dev_info(b4->dev, "(span %d) Frame %d is good!\n", bspan->port + 1, bspan->frames_in);
 			dahdi_hdlc_finish(bspan->sigchan);
-			ret = 1;
 		}
 	}
 
-	return ret;
+	return flen;
 }
 
 
@@ -1615,9 +1628,9 @@ static int hdlc_tx_frame(struct b4xxp_span *bspan)
 {
 	struct b4xxp *b4 = bspan->parent;
 	int res, i, fifo;
-	unsigned int size = 32;
 	int z1, z2, zlen;
-	unsigned char buf[32];
+	unsigned char buf[WCB4XXP_HDLC_BUF_LEN];
+	unsigned int size = sizeof(buf) / sizeof(buf[0]);
 	unsigned long irq_flags;
 
 /* if we're ignoring TE red alarms and we are in alarm, restart the S/T state machine */
@@ -2269,7 +2282,15 @@ static void b4xxp_bottom_half(unsigned long data)
 
 			if (b & V_IRQ_FIFOx_RX) {
 				if (fifo >=8 && fifo <= 11) {
-					hdlc_rx_frame(&b4->spans[fifo - 8]);
+/*
+ * I have to loop here until hdlc_rx_frame says there are no more frames waiting.
+ * for whatever reason, the HFC will not generate another interrupt if there are
+ * still HDLC frames waiting to be received.
+ * i.e. I get an int when F1 changes, not when F1 != F2.
+ */
+					do {
+						k = hdlc_rx_frame(&b4->spans[fifo - 8]);
+					} while (k);
 				} else {
 					if (printk_ratelimit())
 						dev_warn(b4->dev, "Got FIFO RX int from non-d-chan FIFO %d??\n", fifo);