svn commit: r216064 - head/sys/mips/cavium/octe

[Juli Mallett]

Author: jmallett
Date: Mon Nov 29 21:04:00 2010
New Revision: 216064
URL: http://svn.freebsd.org/changeset/base/216064

Log:
  Don't free the work queue entry that we're using to hold the scatter-gather
  list on exit from the transmit path.  The scatter-gather list itself can be
  asynchronously DMAed to the transmit hardware, and we could actually lock up
  the transmitter if any of a number of races around this were lost.
  
  Instead, let the PKO free the scatter-gather list when it is done with it, and
  use the "i" bit in each segment of the packet to avoid having them go into the
  FPA.
  
  This fixes an unrecoverable transmit stall under transmit load.
  
  MFC after:	3 days

Modified:
  head/sys/mips/cavium/octe/ethernet-tx.c

Modified: head/sys/mips/cavium/octe/ethernet-tx.c
==============================================================================
--- head/sys/mips/cavium/octe/ethernet-tx.c	Mon Nov 29 20:43:06 2010	(r216063)
+++ head/sys/mips/cavium/octe/ethernet-tx.c	Mon Nov 29 21:04:00 2010	(r216064)
@@ -143,6 +143,7 @@ int cvm_oct_xmit(struct mbuf *m, struct 
 		/* Build the PKO command */
 		pko_command.u64 = 0;
 		pko_command.s.segs = 1;
+		pko_command.s.dontfree = 1; /* Do not put this buffer into the FPA.  */
 
 		work = NULL;
 	} else {
@@ -164,6 +165,7 @@ int cvm_oct_xmit(struct mbuf *m, struct 
 
 			/* Build the PKO buffer pointer */
 			hw_buffer.u64 = 0;
+			hw_buffer.s.i = 1; /* Do not put this buffer into the FPA.  */
 			hw_buffer.s.addr = cvmx_ptr_to_phys(n->m_data);
 			hw_buffer.s.pool = 0;
 			hw_buffer.s.size = n->m_len;
@@ -182,12 +184,11 @@ int cvm_oct_xmit(struct mbuf *m, struct 
 		pko_command.u64 = 0;
 		pko_command.s.segs = segs;
 		pko_command.s.gather = 1;
+		pko_command.s.dontfree = 0; /* Put the WQE above back into the FPA.  */
 	}
 
 	/* Finish building the PKO command */
 	pko_command.s.n2 = 1; /* Don't pollute L2 with the outgoing packet */
-	pko_command.s.dontfree = 1;
-	pko_command.s.reg0 = priv->fau+qos*4;
 	pko_command.s.reg0 = priv->fau+qos*4;
 	pko_command.s.total_bytes = m->m_pkthdr.len;
 	pko_command.s.size0 = CVMX_FAU_OP_SIZE_32;
@@ -200,6 +201,11 @@ int cvm_oct_xmit(struct mbuf *m, struct 
 		pko_command.s.ipoffp1 = ETHER_HDR_LEN + 1;
 	}
 
+	/*
+	 * XXX
+	 * Could use a different free queue (and different FAU address) per
+	 * core instead of per QoS, to reduce contention here.
+	 */
 	IF_LOCK(&priv->tx_free_queue[qos]);
 	if (USE_ASYNC_IOBDMA) {
 		/* Get the number of mbufs in use by the hardware */
@@ -242,8 +248,6 @@ int cvm_oct_xmit(struct mbuf *m, struct 
 		/* Pass it to any BPF listeners.  */
 		ETHER_BPF_MTAP(ifp, m);
 	}
-	if (work != NULL)
-		cvmx_fpa_free(work, CVMX_FPA_WQE_POOL, DONT_WRITEBACK(1));
 
 	/* Free mbufs not in use by the hardware */
 	if (_IF_QLEN(&priv->tx_free_queue[qos]) > in_use) {