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Date:      Thu, 7 Jul 2016 20:01:03 +0000 (UTC)
From:      Luiz Otavio O Souza <loos@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r302394 - head/sys/arm/ti/cpsw
Message-ID:  <201607072001.u67K13Nh006740@repo.freebsd.org>
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Author: loos
Date: Thu Jul  7 20:01:03 2016
New Revision: 302394
URL: https://svnweb.freebsd.org/changeset/base/302394

Log:
  Fix a lockup in tx path for cspw.
  
  Sometimes the software loses the race when appending more descriptors to
  the tx ring and the tx queue stops.
  
  This commit detects this condition and restart the tx queue whenever it stall.
  
  Tested by:	sobomax@, Keith White <kwhite@site.uottawa.ca>,
  	Paul Mather <paul@gromit.dlib.vt.edu>
  Sponsored by:	Rubicon Communications (Netgate)
  Approved by:	re (kib)

Modified:
  head/sys/arm/ti/cpsw/if_cpsw.c
  head/sys/arm/ti/cpsw/if_cpswvar.h

Modified: head/sys/arm/ti/cpsw/if_cpsw.c
==============================================================================
--- head/sys/arm/ti/cpsw/if_cpsw.c	Thu Jul  7 18:37:12 2016	(r302393)
+++ head/sys/arm/ti/cpsw/if_cpsw.c	Thu Jul  7 20:01:03 2016	(r302394)
@@ -1874,6 +1874,7 @@ cpswp_tx_enqueue(struct cpswp_softc *sc)
 		return;
 	} else if (last_old_slot == NULL) {
 		/* Start a fresh queue. */
+		sc->swsc->last_hdp = cpsw_cpdma_bd_paddr(sc->swsc, first_new_slot);
 		cpsw_write_hdp_slot(sc->swsc, &sc->swsc->tx, first_new_slot);
 	} else {
 		/* Add buffers to end of current queue. */
@@ -1882,6 +1883,7 @@ cpswp_tx_enqueue(struct cpswp_softc *sc)
 		/* If underrun, restart queue. */
 		if (cpsw_cpdma_read_bd_flags(sc->swsc, last_old_slot) &
 		    CPDMA_BD_EOQ) {
+			sc->swsc->last_hdp = cpsw_cpdma_bd_paddr(sc->swsc, first_new_slot);
 			cpsw_write_hdp_slot(sc->swsc, &sc->swsc->tx,
 			    first_new_slot);
 		}
@@ -1897,6 +1899,7 @@ static int
 cpsw_tx_dequeue(struct cpsw_softc *sc)
 {
 	struct cpsw_slot *slot, *last_removed_slot = NULL;
+	struct cpsw_cpdma_bd bd;
 	uint32_t flags, removed = 0;
 
 	slot = STAILQ_FIRST(&sc->tx.active);
@@ -1931,13 +1934,26 @@ cpsw_tx_dequeue(struct cpsw_softc *sc)
 		}
 
 		/* TearDown complete is only marked on the SOP for the packet. */
-		if (flags & CPDMA_BD_TDOWNCMPLT) {
+		if ((flags & (CPDMA_BD_SOP | CPDMA_BD_TDOWNCMPLT)) ==
+		    (CPDMA_BD_EOP | CPDMA_BD_TDOWNCMPLT)) {
 			CPSW_DEBUGF(sc, ("TX teardown in progress"));
 			cpsw_write_cp(sc, &sc->tx, 0xfffffffc);
 			// TODO: Increment a count of dropped TX packets
 			sc->tx.running = 0;
 			break;
 		}
+
+		if ((flags & CPDMA_BD_EOP) == 0)
+			flags = cpsw_cpdma_read_bd_flags(sc, last_removed_slot);
+		if ((flags & (CPDMA_BD_EOP | CPDMA_BD_EOQ)) ==
+		    (CPDMA_BD_EOP | CPDMA_BD_EOQ)) {
+			cpsw_cpdma_read_bd(sc, last_removed_slot, &bd);
+			if (bd.next != 0 && bd.next != sc->last_hdp) {
+				/* Restart the queue. */
+				sc->last_hdp = bd.next;
+				cpsw_write_4(sc, sc->tx.hdp_offset, bd.next);
+			}
+		}
 	}
 
 	if (removed != 0) {

Modified: head/sys/arm/ti/cpsw/if_cpswvar.h
==============================================================================
--- head/sys/arm/ti/cpsw/if_cpswvar.h	Thu Jul  7 18:37:12 2016	(r302393)
+++ head/sys/arm/ti/cpsw/if_cpswvar.h	Thu Jul  7 20:01:03 2016	(r302394)
@@ -83,6 +83,7 @@ struct cpsw_softc {
 
 	/* RX and TX buffer tracking */
 	struct cpsw_queue rx, tx;
+	uint32_t	last_hdp;
 
 	/* We expect 1 memory resource and 4 interrupts from the device tree. */
 	int		mem_rid;

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