From 1299160d1d9aff2cc15d55718ff84ded1ffba90f Mon Sep 17 00:00:00 2001
From: Gregory Nutt <gnutt@nuttx.org>
Date: Tue, 3 Nov 2015 10:47:37 -0600
Subject: [PATCH] SAMV71-XULT: Add call to can_txready() to MCAN driver.  This
 is part of a fix to a CAN hang problem

---
 arch/arm/src/samv7/Kconfig    |  2 ++
 arch/arm/src/samv7/sam_mcan.c | 14 ++++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/arch/arm/src/samv7/Kconfig b/arch/arm/src/samv7/Kconfig
index 3dede34314e..7aa5707bd0c 100644
--- a/arch/arm/src/samv7/Kconfig
+++ b/arch/arm/src/samv7/Kconfig
@@ -223,6 +223,7 @@ config SAMV7_MCAN0
 	bool "CAN controller 0 (MCAN0)"
 	default n
 	select CAN
+	select CAN_TXREADY
 	select SAMV7_MCAN
 
 config SAMV7_MCAN1
@@ -230,6 +231,7 @@ config SAMV7_MCAN1
 	default n
 	depends on SAMV7_HAVE_MCAN1
 	select CAN
+	select CAN_TXREADY
 	select SAMV7_MCAN
 
 config SAMV7_DAC0
diff --git a/arch/arm/src/samv7/sam_mcan.c b/arch/arm/src/samv7/sam_mcan.c
index 1fcefd32c71..b72a08d4df6 100644
--- a/arch/arm/src/samv7/sam_mcan.c
+++ b/arch/arm/src/samv7/sam_mcan.c
@@ -128,6 +128,12 @@
 #  endif
 #endif
 
+/* General Configuration ****************************************************/
+
+#ifndef CONFIG_CAN_TXREADY
+#  warning WARNING!!! CONFIG_CAN_TXREADY is required by this driver
+#endif
+
 /* MCAN0 Configuration ******************************************************/
 
 #ifdef CONFIG_SAMV7_MCAN0
@@ -3190,6 +3196,14 @@ static void mcan_interrupt(FAR struct can_dev_s *dev)
 
           mcan_buffer_release(priv);
           handled = true;
+
+#ifdef CONFIG_CAN_TXREADY
+          /* Inform the upper half driver that we are again ready to accept
+           * data in mcan_send().
+           */
+
+          can_txready(dev);
+#endif
         }
       else if ((pending & priv->txints) != 0)
         {