Work around a start-up error in the GMAC that I still do not understand

1 files changed, 24 insertions, 2 deletions

diff --git a/nuttx/arch/arm/src/sama5/sam_emac.c b/nuttx/arch/arm/src/sama5/sam_emac.c
index 878e43ca2..c169bacb6 100644
--- a/nuttx/arch/arm/src/sama5/sam_emac.c
+++ b/nuttx/arch/arm/src/sama5/sam_emac.c
@@ -1247,9 +1247,31 @@ static void sam_txdone(struct sam_emac_s *priv)
 
       if ((txdesc->status & EMACTXD_STA_USED) == 0)
         {
-          /* Yes ... break out of the loop now */
+          /* Yes.. the descriptor is still in use.  However, I have seen a
+           * case (only repeatable on start-up) where the USED bit is never
+           * set.  Yikes!  If we have encountered the first still busy
+           * descriptor, then we should also have TQBD equal to the descriptor
+           * address.  If it is not, then treat is as used anyway.
+           */
 
-          break;
+#if 0 /* The issue does not exist in the current configuration, but may return */
+#warning REVISIT
+          if (priv->txtail == 0 &&
+              sam_physramaddr((uintprt_t)txdesc) != sam_getreg(priv, SAM_EMAC_TBQP))
+            {
+              txdesc->status = (uint32_t)EMACTXD_STA_USED;
+              cp15_clean_dcache((uintptr_t)txdesc,
+                                (uintptr_t)txdesc + sizeof(struct emac_txdesc_s));
+            }
+          else
+#endif
+            {
+              /* Otherwise, the descriptor is truly in use.  Break out of the
+               * loop now.
+               */
+
+              break;
+            }
         }
 
       /* Increment the tail index */