Add SAM3/4 RTT driver. From Bob Doiron

5 files changed, 923 insertions, 30 deletions

diff --git a/nuttx/arch/arm/src/sam34/Make.defs b/nuttx/arch/arm/src/sam34/Make.defs
index efd7e2326..c09eeab73 100644
--- a/nuttx/arch/arm/src/sam34/Make.defs
+++ b/nuttx/arch/arm/src/sam34/Make.defs
@@ -134,6 +134,10 @@ ifeq ($(CONFIG_SAM34_RTC),y)
 CHIP_CSRCS += sam_rtc.c
 endif
 
+ifeq ($(CONFIG_SAM34_RTT),y)
+CHIP_CSRCS += sam_rtt.c
+endif
+
 ifeq ($(CONFIG_SAM34_WDT),y)
 CHIP_CSRCS += sam_wdt.c
 endif
diff --git a/nuttx/arch/arm/src/sam34/sam_rtc.c b/nuttx/arch/arm/src/sam34/sam_rtc.c
index 0bdb028d2..9b4e8b40f 100644
--- a/nuttx/arch/arm/src/sam34/sam_rtc.c
+++ b/nuttx/arch/arm/src/sam34/sam_rtc.c
@@ -54,20 +54,25 @@
 #include "up_arch.h"
 #include "sam_rtc.h"
 
+#if defined(CONFIG_RTC_HIRES) && defined (CONFIG_SAM34_RTT)
+#  include "sam_rtt.h"
+#  include "sam_periphclks.h"
+#endif
+
 #ifdef CONFIG_RTC
 
 /************************************************************************************
  * Pre-processor Definitions
  ************************************************************************************/
 /* Configuration ********************************************************************/
-/* This RTC implementation supports only date/time RTC hardware */
-
-#ifndef CONFIG_RTC_DATETIME
-#  error "CONFIG_RTC_DATETIME must be set to use this driver"
-#endif
 
 #ifdef CONFIG_RTC_HIRES
-#  error "CONFIG_RTC_HIRES must NOT be set with this driver"
+# if !defined(CONFIG_SAM34_RTT)
+#  error RTT is required to emulate high resolution RTC
+# endif
+# if (CONFIG_RTC_FREQUENCY > 32768) || ((32768 % CONFIG_RTC_FREQUENCY) != 0)
+#  error CONFIG_RTC_FREQUENCY must be an integer division of 32768
+# endif
 #endif
 
 #if defined(CONFIG_RTC_ALARM) && !defined(CONFIG_SCHED_WORKQUEUE)
@@ -119,6 +124,12 @@ struct work_s g_alarmwork;
 
 volatile bool g_rtc_enabled = false;
 
+/* g_rtt_offset holds the rtt->rtc count offset */
+
+#if defined(CONFIG_RTC_HIRES) && defined (CONFIG_SAM34_RTT)
+uint32_t g_rtt_offset = 0;
+#endif
+
 /************************************************************************************
  * Private Functions
  ************************************************************************************/
@@ -303,6 +314,40 @@ static int rtc_interrupt(int irq, void *context)
 #endif
 
 /************************************************************************************
+ * Name: rtc_sync
+ *
+ * Description:
+ *   Waits and returns immediately after 1 sec tick. For best accuracy,
+ *   call with interrupts disabled.
+ *
+ * Returns value of the TIMR register
+ *
+ ************************************************************************************/
+
+static uint32_t rtc_sync(void)
+{
+  uint32_t r0, r1;
+
+  /* Get start second (stable) */
+
+  do
+    {
+      r0 = getreg32(SAM_RTC_TIMR);
+    }
+  while (r0 != getreg32(SAM_RTC_TIMR));
+
+  /* Now read until it changes */
+
+  do
+    {
+      r1 = getreg32(SAM_RTC_TIMR);
+    }
+  while (r1 == r0);
+
+  return r1;
+}
+
+/************************************************************************************
  * Public Functions
  ************************************************************************************/
 
@@ -370,6 +415,32 @@ int up_rtcinitialize(void)
 
 #endif
 
+#if defined(CONFIG_RTC_HIRES) && defined (CONFIG_SAM34_RTT)
+   /* Using the RTT for subsecond ticks. */
+
+  sam_rtt_enableclk();
+
+  /* Disable ints, set prescaler, start counter */
+
+  putreg32(RTT_MR_RTPRES(32768/CONFIG_RTC_FREQUENCY) | RTT_MR_RTTRST, SAM_RTT_MR);
+
+  /* wait for a second tick to get the RTT offset.
+   * Interrupts are assumed to still be off at this point.
+   */
+
+  rtc_sync();
+
+  /* Probably safe to read the RTT_VR register now since the clock just ticked,
+   * but we'll be careful anyway.
+   */
+
+  do
+    {
+      g_rtt_offset = getreg32(SAM_RTT_VR);
+    }
+  while(getreg32(SAM_RTT_VR) != g_rtt_offset);
+#endif
+
   rtc_dumpregs("After Initialization");
   return OK;
 }
@@ -681,4 +752,55 @@ int up_rtc_setalarm(FAR const struct timespec *tp, alarmcb_t callback)
 }
 #endif
 
+
+/************************************************************************************
+ * Name: up_rtc_gettime
+ *
+ * Description:
+ *   Get the current time from the high resolution RTC clock/counter.  This interface
+ *   is only supported by the high-resolution RTC/counter hardware implementation.
+ *   It is used to replace the system timer.
+ *
+ * Input Parameters:
+ *   tp - The location to return the high resolution time value.
+ *
+ * Returned Value:
+ *   Zero (OK) on success; a negated errno on failure
+ *
+ ************************************************************************************/
+
+#if defined(CONFIG_RTC_HIRES) && defined (CONFIG_SAM34_RTT)
+
+int up_rtc_gettime(FAR struct timespec *tp)
+{
+  /* This is a hack to emulate a high resolution rtc using the rtt */
+  uint32_t rtc_cal, rtc_tim, rtt_val;
+  struct tm t;
+
+  do
+  {
+    rtc_cal = getreg32(SAM_RTC_CALR);
+    rtc_tim = getreg32(SAM_RTC_TIMR);
+    rtt_val = getreg32(SAM_RTT_VR);
+  } while((rtc_cal != getreg32(SAM_RTC_CALR)) ||
+          (rtc_tim != getreg32(SAM_RTC_TIMR)) ||
+          (rtt_val != getreg32(SAM_RTT_VR)));
+
+  t.tm_sec  = rtc_bcd2bin((rtc_tim & RTC_TIMR_SEC_MASK)   >> RTC_TIMR_SEC_SHIFT);
+  t.tm_min  = rtc_bcd2bin((rtc_tim & RTC_TIMR_MIN_MASK)   >> RTC_TIMR_MIN_SHIFT);
+  t.tm_hour = rtc_bcd2bin((rtc_tim & RTC_TIMR_HOUR_MASK)  >> RTC_TIMR_HOUR_SHIFT);
+  t.tm_mday = rtc_bcd2bin((rtc_cal & RTC_CALR_DATE_MASK)  >> RTC_CALR_DATE_SHIFT);
+  t.tm_mon  = rtc_bcd2bin((rtc_cal & RTC_CALR_MONTH_MASK) >> RTC_CALR_MONTH_SHIFT);
+  t.tm_year = (rtc_bcd2bin((rtc_cal & RTC_CALR_CENT_MASK) >> RTC_CALR_CENT_SHIFT) * 100)
+             + rtc_bcd2bin((rtc_cal & RTC_CALR_YEAR_MASK) >> RTC_CALR_YEAR_SHIFT)
+             - 1900;
+
+  tp->tv_sec = mktime(&t);
+  tp->tv_nsec = (((rtt_val-g_rtt_offset) & (CONFIG_RTC_FREQUENCY-1)) * 1000000000ULL) /
+                CONFIG_RTC_FREQUENCY;
+
+  return OK;
+}
+#endif
+
 #endif /* CONFIG_RTC */
diff --git a/nuttx/arch/arm/src/sam34/sam_rtt.c b/nuttx/arch/arm/src/sam34/sam_rtt.c
new file mode 100644
index 000000000..fc9ddd170
--- /dev/null
+++ b/nuttx/arch/arm/src/sam34/sam_rtt.c
@@ -0,0 +1,668 @@
+/****************************************************************************
+ * arch/arm/src/sam34/sam_rtt.c
+ *
+ *   Copyright (C) 2014 Gregory Nutt. All rights reserved.
+ *   Authors: Gregory Nutt <gnutt@nuttx.org>
+ *            Bob Dioron
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+#include <nuttx/arch.h>
+
+#include <sys/types.h>
+
+#include <stdint.h>
+#include <errno.h>
+#include <debug.h>
+#include <nuttx/timer.h>
+#include <arch/board/board.h>
+
+#include "up_arch.h"
+#include "sam_rtt.h"
+#include "sam_periphclks.h"
+
+#if defined(CONFIG_TIMER) && (defined(CONFIG_SAM34_RTT))
+
+/****************************************************************************
+ * Pre-Processor Definitions
+ ****************************************************************************/
+/* Clocking *****************************************************************/
+
+#if defined(CONFIG_RTC_HIRES) && defined (CONFIG_SAM34_RTC)
+#  define RTT_PRES      (32768/CONFIG_RTC_FREQUENCY)
+#else
+/* TODO: Allow prescaler selection. */
+#  define RTT_PRES      1
+#endif
+
+#define RTT_FCLK        (BOARD_SLCK_FREQUENCY/RTT_PRES)
+#define RTT_MAXTIMEOUT  ((1000000ULL * (0x100000000ULL)) / RTT_FCLK)
+
+/* Configuration ************************************************************/
+
+/* Debug ********************************************************************/
+/* Non-standard debug that may be enabled just for testing the timer
+ * driver.  NOTE: that only lldbg types are used so that the output is
+ * immediately available.
+ */
+
+#ifdef CONFIG_DEBUG_RTT
+#  define rttdbg    lldbg
+#  define rttvdbg   llvdbg
+#else
+#  define rttdbg(x...)
+#  define rttvdbg(x...)
+#endif
+
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+/* This structure provides the private representation of the "lower-half"
+ * driver state structure.  This structure must be cast-compatible with the
+ * timer_lowerhalf_s structure.
+ */
+
+struct sam34_lowerhalf_s
+{
+  FAR const struct timer_ops_s  *ops;  /* Lower half operations */
+
+  /* Private data */
+
+  tccb_t   handler;         /* Current user interrupt handler */
+  uint32_t timeout;         /* The current timeout value (us) */
+  uint32_t clkticks;        /* actual clock ticks for current interval */
+  uint32_t val;             /* rtt value of current timeout */
+  uint32_t adjustment;      /* time lost due to clock resolution truncation (us) */
+  bool     started;         /* The timer has been started */
+};
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+/* Register operations ******************************************************/
+
+#if defined(CONFIG_SAM34_RTT_REGDEBUG) && defined(CONFIG_DEBUG)
+static uint32_t sam34_getreg(uint32_t addr);
+static void     sam34_putreg(uint32_t val, uint32_t addr);
+#else
+# define        sam34_getreg(addr)     getreg32(addr)
+# define        sam34_putreg(val,addr) putreg32(val,addr)
+#endif
+
+/* Interrupt handling *******************************************************/
+
+static int      sam34_interrupt(int irq, FAR void *context);
+
+/* "Lower half" driver methods **********************************************/
+
+static int      sam34_start(FAR struct timer_lowerhalf_s *lower);
+static int      sam34_stop(FAR struct timer_lowerhalf_s *lower);
+static int      sam34_getstatus(FAR struct timer_lowerhalf_s *lower,
+                  FAR struct timer_status_s *status);
+static int      sam34_settimeout(FAR struct timer_lowerhalf_s *lower,
+                  uint32_t timeout);
+static tccb_t   sam34_sethandler(FAR struct timer_lowerhalf_s *lower,
+                  tccb_t handler);
+static int      sam34_ioctl(FAR struct timer_lowerhalf_s *lower, int cmd,
+                  unsigned long arg);
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+/* "Lower half" driver methods */
+
+static const struct timer_ops_s g_tcops =
+{
+  .start      = sam34_start,
+  .stop       = sam34_stop,
+  .getstatus  = sam34_getstatus,
+  .settimeout = sam34_settimeout,
+  .sethandler = sam34_sethandler,
+  .ioctl      = sam34_ioctl,
+};
+
+/* "Lower half" driver state */
+
+static struct sam34_lowerhalf_s g_tcdev;
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: sam34_readvr
+ *
+ * Description:
+ *   Get the contents of the value register.
+ *
+ ****************************************************************************/
+static inline uint32_t sam34_readvr(void)
+{
+  register uint32_t v;
+
+  /* Async counter, read until two consecutive reads match */
+
+  do
+    {
+      v = getreg32(SAM_RTT_VR);
+    }
+  while(v != getreg32(SAM_RTT_VR));
+
+  return v;
+}
+
+/****************************************************************************
+ * Name: sam34_getreg
+ *
+ * Description:
+ *   Get the contents of a register
+ *
+ ****************************************************************************/
+
+#if defined(CONFIG_SAM34_RTT_REGDEBUG) && defined(CONFIG_DEBUG)
+static uint32_t sam34_getreg(uint32_t addr)
+{
+  static uint32_t prevaddr = 0;
+  static uint32_t count = 0;
+  static uint32_t preval = 0;
+
+  /* Read the value from the register */
+
+  uint32_t val = getreg32(addr);
+
+  /* Is this the same value that we read from the same registe last time?  Are
+   * we polling the register?  If so, suppress some of the output.
+   */
+
+  if (addr == prevaddr && val == preval)
+    {
+      if (count == 0xffffffff || ++count > 3)
+        {
+           if (count == 4)
+             {
+               lldbg("...\n");
+             }
+
+          return val;
+        }
+    }
+
+  /* No this is a new address or value */
+
+  else
+    {
+       /* Did we print "..." for the previous value? */
+
+       if (count > 3)
+         {
+           /* Yes.. then show how many times the value repeated */
+
+           lldbg("[repeats %d more times]\n", count-3);
+         }
+
+       /* Save the new address, value, and count */
+
+       prevaddr = addr;
+       preval   = val;
+       count    = 1;
+    }
+
+  /* Show the register value read */
+
+  lldbg("%08lx->%08lx\n", addr, val);
+  return val;
+}
+#endif
+
+/****************************************************************************
+ * Name: sam34_putreg
+ *
+ * Description:
+ *   Set the contents of an SAM34 register to a value
+ *
+ ****************************************************************************/
+
+#if defined(CONFIG_SAM34_RTT_REGDEBUG) && defined(CONFIG_DEBUG)
+static void sam34_putreg(uint32_t val, uint32_t addr)
+{
+  /* Show the register value being written */
+
+  lldbg("%08lx<-%08lx\n", addr, val);
+
+  /* Write the value */
+
+  putreg32(val, addr);
+}
+#endif
+
+/****************************************************************************
+ * Name: sam34_interrupt
+ *
+ * Description:
+ *   TC interrupt
+ *
+ * Input Parameters:
+ *   Usual interrupt handler arguments.
+ *
+ * Returned Values:
+ *   Always returns OK.
+ *
+ ****************************************************************************/
+
+static int sam34_interrupt(int irq, FAR void *context)
+{
+  FAR struct sam34_lowerhalf_s *priv = &g_tcdev;
+
+  rttvdbg("Entry\n");
+  DEBUGASSERT(irq == SAM_IRQ_RTT);
+
+  /* Check if the interrupt is really pending */
+
+  if ((sam34_getreg(SAM_RTT_SR) & RTT_SR_ALMS) != 0)
+    {
+      uint32_t timeout;
+      uint32_t mrval;
+      uint32_t vr;
+      uint32_t lateticks;
+
+      /* Is there a registered handler? */
+
+      if (priv->handler && priv->handler(&priv->timeout))
+        {
+          /* Disable int before writing new alarm */
+
+          mrval = sam34_getreg(SAM_RTT_MR);
+          sam34_putreg(mrval & ~RTT_MR_ALMIEN, SAM_RTT_MR);
+
+          /* Calculate new ticks / dither adjustment */
+
+          vr = sam34_readvr();
+          priv->clkticks =
+            ((uint64_t)(priv->adjustment + priv->timeout)) * RTT_FCLK / 1000000;
+
+          /* Subtract off how late we are, but only up to half an interval.
+           * TODO calculate lost ticks?
+           */
+
+          lateticks = vr - priv->val;
+          if (lateticks <= (priv->clkticks>>1))
+            {
+              priv->clkticks -= lateticks;
+            }
+
+          /* Set next interval interval. */
+
+          priv->val = vr + priv->clkticks;
+          sam34_putreg(priv->val-1, SAM_RTT_AR);
+
+          /* Re-enable alarm */
+
+          sam34_putreg(mrval, SAM_RTT_MR);
+
+          /* Truncated timeout */
+
+          timeout = (1000000ULL * priv->clkticks) / RTT_FCLK;
+
+          /* Truncated time to be added to next interval (dither) */
+
+          priv->adjustment = (priv->adjustment + priv->timeout) - timeout;
+        }
+      else /* stop */
+        {
+          sam34_stop((FAR struct timer_lowerhalf_s *)priv);
+        }
+
+      /* RTT_SR_ALMS is cleared by reading SAM_RTT_SR */
+    }
+
+  return OK;
+}
+
+/****************************************************************************
+ * Name: sam34_start
+ *
+ * Description:
+ *   Start the timer, resetting the time to the current timeout,
+ *
+ * Input Parameters:
+ *   lower - A pointer the publicly visible representation of the "lower-half"
+ *           driver state structure.
+ *
+ * Returned Values:
+ *   Zero on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+static int sam34_start(FAR struct timer_lowerhalf_s *lower)
+{
+  FAR struct sam34_lowerhalf_s *priv = (FAR struct sam34_lowerhalf_s *)lower;
+  uint32_t mr;
+  uint32_t vr;
+
+  rttvdbg("Entry\n");
+  DEBUGASSERT(priv);
+
+  if (priv->started)
+    {
+      return -EINVAL;
+    }
+
+#if defined(CONFIG_RTC_HIRES) && defined (CONFIG_SAM34_RTC)
+  /* RTT is started with the RTC and always on */
+
+  mr = sam34_getreg(SAM_RTT_MR) & ~RTT_MR_ALMIEN;
+  sam34_putreg(mr, SAM_RTT_MR);
+  vr = sam34_readvr();
+
+#else
+  sam_rtt_enableclk();                   /* Enable peripheral clock */
+  mr = RTT_MR_RTPRES(RTT_PRES);
+  sam34_putreg(mr, SAM_RTT_MR);          /* Set prescaler, disable ints */
+  vr = 0;                                /* we're going to reset the counter */
+#endif
+
+  priv->val = vr + priv->clkticks;       /* value at end of interval */
+  sam34_putreg(priv->val-1, SAM_RTT_AR); /* Set interval */
+
+  if (priv->handler)
+    {
+      /* Clear status and enable interrupt */
+
+      sam34_getreg(SAM_RTT_SR);
+      mr |= RTT_MR_ALMIEN;
+      sam34_putreg(mr, SAM_RTT_MR);
+    }
+
+#if !(defined(CONFIG_RTC_HIRES) && defined (CONFIG_SAM34_RTC))
+  sam34_putreg(mr | RTT_MR_RTTRST, SAM_RTT_MR); /* Start counter */
+#endif /* !(CONFIG_RTC_HIRES && CONFIG_SAM34_RTC) */
+
+  priv->started = true;
+  return OK;
+}
+
+/****************************************************************************
+ * Name: sam34_stop
+ *
+ * Description:
+ *   Stop the timer
+ *
+ * Input Parameters:
+ *   lower - A pointer the publicly visible representation of the "lower-half"
+ *           driver state structure.
+ *
+ * Returned Values:
+ *   Zero on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+static int sam34_stop(FAR struct timer_lowerhalf_s *lower)
+{
+  FAR struct sam34_lowerhalf_s *priv = (FAR struct sam34_lowerhalf_s *)lower;
+  rttvdbg("Entry\n");
+  DEBUGASSERT(priv);
+
+  if(!priv->started)
+    {
+      return -EINVAL;
+    }
+
+#if !(defined(CONFIG_RTC_HIRES) && defined (CONFIG_SAM34_RTC))
+  sam34_putreg(RTT_MR_RTTDIS, SAM_RTT_MR);    /* Disable RTT */
+  sam_rtt_disableclk();                       /* Disable peripheral clock */
+#endif
+
+  priv->started = false;
+
+  return OK;
+}
+
+/****************************************************************************
+ * Name: sam34_getstatus
+ *
+ * Description:
+ *   Get the current timer status
+ *
+ * Input Parameters:
+ *   lower  - A pointer the publicly visible representation of the "lower-half"
+ *            driver state structure.
+ *   status - The location to return the status information.
+ *
+ * Returned Values:
+ *   Zero on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+static int sam34_getstatus(FAR struct timer_lowerhalf_s *lower,
+                           FAR struct timer_status_s *status)
+{
+  FAR struct sam34_lowerhalf_s *priv = (FAR struct sam34_lowerhalf_s *)lower;
+
+  rttvdbg("Entry\n");
+  DEBUGASSERT(priv);
+
+  /* Return the status bit */
+
+  status->flags = 0;
+  if (priv->started)
+    {
+      status->flags |= TCFLAGS_ACTIVE;
+    }
+
+  if (priv->handler)
+    {
+      status->flags |= TCFLAGS_HANDLER;
+    }
+
+  /* Return the actual timeout is milliseconds */
+
+  status->timeout = priv->timeout;
+
+  /* Get the time remaining until the timer expires (in microseconds) */
+
+  status->timeleft = 1000000ULL*(sam34_getreg(SAM_RTT_AR) - sam34_readvr())/RTT_FCLK;
+
+  rttvdbg("  flags    : %08x\n", status->flags);
+  rttvdbg("  timeout  : %d\n", status->timeout);
+  rttvdbg("  timeleft : %d\n", status->timeleft);
+  return OK;
+}
+
+/****************************************************************************
+ * Name: sam34_settimeout
+ *
+ * Description:
+ *   Set a new timeout value (and reset the timer)
+ *
+ * Input Parameters:
+ *   lower   - A pointer the publicly visible representation of the "lower-half"
+ *             driver state structure.
+ *   timeout - The new timeout value in milliseconds.
+ *
+ * Returned Values:
+ *   Zero on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+static int sam34_settimeout(FAR struct timer_lowerhalf_s *lower,
+                            uint32_t timeout)
+{
+  FAR struct sam34_lowerhalf_s *priv = (FAR struct sam34_lowerhalf_s *)lower;
+
+  DEBUGASSERT(priv);
+  rttvdbg("Entry: timeout=%d\n", timeout);
+
+  if(priv->started) return -EPERM;
+
+  /* Can this timeout be represented? */
+
+  if (timeout < 1 || timeout > RTT_MAXTIMEOUT)
+    {
+      rttdbg("Cannot represent timeout=%lu > %lu\n",
+            timeout, RTT_MAXTIMEOUT);
+      return -ERANGE;
+    }
+
+  priv->timeout = timeout;                                     /* Intended timeout */
+  priv->clkticks = (((uint64_t)timeout * RTT_FCLK) / 1000000); /* Actual clock ticks */
+  timeout = (1000000ULL * priv->clkticks) / RTT_FCLK;          /* Truncated timeout */
+  priv->adjustment = priv->timeout - timeout;                  /* Truncated time to be added to next interval (dither) */
+
+  rttvdbg("fclk=%d clkticks=%d timout=%d, adjustment=%d\n",
+         RTT_FCLK, priv->clkticks, priv->timeout, priv->adjustment);
+
+  return OK;
+}
+
+/****************************************************************************
+ * Name: sam34_sethandler
+ *
+ * Description:
+ *   Call this user provided timeout handler.
+ *
+ * Input Parameters:
+ *   lower      - A pointer the publicly visible representation of the "lower-half"
+ *                driver state structure.
+ *   newhandler - The new timer expiration function pointer.  If this
+ *                function pointer is NULL, then the reset-on-expiration
+ *                behavior is restored,
+ *
+ * Returned Values:
+ *   The previous timer expiration function pointer or NULL is there was
+ *   no previous function pointer.
+ *
+ ****************************************************************************/
+
+static tccb_t sam34_sethandler(FAR struct timer_lowerhalf_s *lower,
+                               tccb_t handler)
+{
+  FAR struct sam34_lowerhalf_s *priv = (FAR struct sam34_lowerhalf_s *)lower;
+  irqstate_t flags;
+  tccb_t oldhandler;
+
+  flags = irqsave();
+
+  DEBUGASSERT(priv);
+  rttvdbg("Entry: handler=%p\n", handler);
+
+  /* Get the old handler return value */
+
+  oldhandler = priv->handler;
+
+  /* Save the new handler */
+
+   priv->handler = handler;
+
+  irqrestore(flags);
+  return oldhandler;
+}
+
+/****************************************************************************
+ * Name: sam34_ioctl
+ *
+ * Description:
+ *   Any ioctl commands that are not recognized by the "upper-half" driver
+ *   are forwarded to the lower half driver through this method.
+ *
+ * Input Parameters:
+ *   lower - A pointer the publicly visible representation of the "lower-half"
+ *           driver state structure.
+ *   cmd   - The ioctl command value
+ *   arg   - The optional argument that accompanies the 'cmd'.  The
+ *           interpretation of this argument depends on the particular
+ *           command.
+ *
+ * Returned Values:
+ *   Zero on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+static int sam34_ioctl(FAR struct timer_lowerhalf_s *lower, int cmd,
+                    unsigned long arg)
+{
+  FAR struct sam34_lowerhalf_s *priv = (FAR struct sam34_lowerhalf_s *)lower;
+  int ret = -ENOTTY;
+
+  DEBUGASSERT(priv);
+  rttvdbg("Entry: cmd=%d arg=%ld\n", cmd, arg);
+
+  return ret;
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: sam_rttinitialize
+ *
+ * Description:
+ *   Initialize the timer.  The timer is initialized and registers as
+ *   'devpath'.
+ *
+ * Input Parameters:
+ *   devpath - The full path to the timer.  This should be of the form
+ *     /dev/rtt0
+ *
+ * Returned Values:
+ *   None
+ *
+ ****************************************************************************/
+
+void sam_rttinitialize(FAR const char *devpath)
+{
+  FAR struct sam34_lowerhalf_s *priv = &g_tcdev;
+
+  rttvdbg("Entry: devpath=%s\n", devpath);
+
+  /* Initialize the driver state structure.  Here we assume: (1) the state
+   * structure lies in .bss and was zeroed at reset time.  (2) This function
+   * is only called once so it is never necessary to re-zero the structure.
+   */
+
+  priv->ops = &g_tcops;
+
+  (void)irq_attach(SAM_IRQ_RTT, sam34_interrupt);
+
+  /* Enable NVIC interrupt. */
+
+  up_enable_irq(SAM_IRQ_RTT);
+
+  /* Register the timer driver as /dev/timerX */
+
+  (void)timer_register(devpath, (FAR struct timer_lowerhalf_s *)priv);
+}
+
+#endif /* CONFIG_TIMER && CONFIG_SAM34_TCx */
diff --git a/nuttx/arch/arm/src/sam34/sam_rtt.h b/nuttx/arch/arm/src/sam34/sam_rtt.h
new file mode 100644
index 000000000..f300747ef
--- /dev/null
+++ b/nuttx/arch/arm/src/sam34/sam_rtt.h
@@ -0,0 +1,100 @@
+/****************************************************************************
+ * arch/arm/src/sam34/sam_rtt.h
+ *
+ *   Copyright (C) 2014 Gregory Nutt. All rights reserved.
+ *   Authors: Gregory Nutt <gnutt@nuttx.org>
+ *            Bob Doiron
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+#ifndef __ARCH_ARM_SRC_SAM34_RTT_H
+#define __ARCH_ARM_SRC_SAM34_RTT_H
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include "chip.h"
+#include "chip/sam_rtt.h"
+
+#ifdef CONFIG_TIMER
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+#ifndef __ASSEMBLY__
+
+#undef EXTERN
+#if defined(__cplusplus)
+#define EXTERN extern "C"
+extern "C"
+{
+#else
+#define EXTERN extern
+#endif
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+#if defined(CONFIG_SAM34_RTT)
+
+/****************************************************************************
+ * Name: sam_rttinitialize
+ *
+ * Description:
+ *   Initialize the timer.  The timer is initialized and registers as
+ *   'devpath.  The initial state of the timer is disabled.
+ *
+ * Input Parameters:
+ *   devpath - The full path to the timer.  This should be of the form
+ *     /dev/rtt0
+ *
+ * Returned Values:
+ *   None
+ *
+ ****************************************************************************/
+
+void sam_rttinitialize(FAR const char *devpath);
+
+#endif // CONFIG_SAM34_RTT
+
+
+#undef EXTERN
+#if defined(__cplusplus)
+}
+#endif
+
+#endif /* __ASSEMBLY__ */
+#endif /* CONFIG_TIMER */
+#endif /* __ARCH_ARM_SRC_SAM34_RTT_H */
diff --git a/nuttx/arch/arm/src/sam34/sam_tc.c b/nuttx/arch/arm/src/sam34/sam_tc.c
index 27dbd1642..b955d6bb0 100644
--- a/nuttx/arch/arm/src/sam34/sam_tc.c
+++ b/nuttx/arch/arm/src/sam34/sam_tc.c
@@ -106,7 +106,6 @@ struct sam34_lowerhalf_s
   uint32_t clkticks;        /* actual clock ticks for current interval */
   bool     started;         /* The timer has been started */
   uint16_t periphid;        /* peripheral id */
-  uint16_t debug;
 };
 
 /****************************************************************************
@@ -134,7 +133,7 @@ static int      sam34_getstatus(FAR struct timer_lowerhalf_s *lower,
                   FAR struct timer_status_s *status);
 static int      sam34_settimeout(FAR struct timer_lowerhalf_s *lower,
                   uint32_t timeout);
-static tccb_t   sam34_capture(FAR struct timer_lowerhalf_s *lower,
+static tccb_t   sam34_sethandler(FAR struct timer_lowerhalf_s *lower,
                   tccb_t handler);
 static int      sam34_ioctl(FAR struct timer_lowerhalf_s *lower, int cmd,
                   unsigned long arg);
@@ -150,7 +149,7 @@ static const struct timer_ops_s g_tcops =
   .stop       = sam34_stop,
   .getstatus  = sam34_getstatus,
   .settimeout = sam34_settimeout,
-  .capture    = sam34_capture,
+  .sethandler = sam34_sethandler,
   .ioctl      = sam34_ioctl,
 };
 
@@ -267,15 +266,13 @@ static void sam34_putreg(uint32_t val, uint32_t addr)
 static int sam34_interrupt(int irq, FAR void *context)
 {
   FAR struct sam34_lowerhalf_s *priv = &g_tcdevs[irq-SAM_IRQ_TC0];
-  uint16_t regval;
 
   tcvdbg("Entry\n");
   DEBUGASSERT((irq >= SAM_IRQ_TC0) && (irq <= SAM_IRQ_TC5));
 
   /* Check if the interrupt is really pending */
 
-  regval = sam34_getreg(priv->base + SAM_TC_SR_OFFSET);
-  if ((regval & TC_INT_CPCS) != 0)
+  if ((sam34_getreg(priv->base + SAM_TC_SR_OFFSET) & TC_INT_CPCS) != 0)
     {
       uint32_t timeout;
 
@@ -283,7 +280,7 @@ static int sam34_interrupt(int irq, FAR void *context)
 
       if (priv->handler && priv->handler(&priv->timeout))
         {
-          /* Calculate new ticks */
+          /* Calculate new ticks / dither adjustment */
 
           priv->clkticks = ((uint64_t)(priv->adjustment + priv->timeout))*TC_FCLK / 1000000;
 
@@ -323,7 +320,7 @@ static int sam34_interrupt(int irq, FAR void *context)
 static int sam34_start(FAR struct timer_lowerhalf_s *lower)
 {
   FAR struct sam34_lowerhalf_s *priv = (FAR struct sam34_lowerhalf_s *)lower;
-  uint32_t mr_val = 0;
+  uint32_t mr_val;
 
   tcvdbg("Entry\n");
   DEBUGASSERT(priv);
@@ -335,13 +332,14 @@ static int sam34_start(FAR struct timer_lowerhalf_s *lower)
 
   sam_enableperiph0(priv->periphid);                            /* Enable peripheral clock */
   sam34_putreg(TC_CCR_CLKDIS, priv->base + SAM_TC_CCR_OFFSET);  /* Disable counter */
+  sam34_putreg(0, priv->base + SAM_TC_CV_OFFSET);               /* clear counter */
 
   /* TC_CMR_WAVE - waveform mode
    * TC_CMR_WAVSEL_UPAUTO - reset on RC compare (interval timer)
    * TC_CMR_TCCLKS_TIMERCLOCK5 = SCLK
    */
 
-  mr_val |= (TC_CMR_WAVE + TC_CMR_WAVSEL_UPAUTO + TC_CMR_TCCLKS_TIMERCLOCK5);
+  mr_val = (TC_CMR_WAVE + TC_CMR_WAVSEL_UPAUTO + TC_CMR_TCCLKS_TIMERCLOCK5);
   sam34_putreg(mr_val, priv->base + SAM_TC_CMR_OFFSET);
 
   sam34_putreg(priv->clkticks, priv->base + SAM_TC_RC_OFFSET);   /* Set interval */
@@ -381,7 +379,7 @@ static int sam34_stop(FAR struct timer_lowerhalf_s *lower)
   tcvdbg("Entry\n");
   DEBUGASSERT(priv);
 
-  if(!priv->started)
+  if (!priv->started)
     {
       return -EINVAL;
     }
@@ -430,7 +428,7 @@ static int sam34_getstatus(FAR struct timer_lowerhalf_s *lower,
 
   if (priv->handler)
     {
-      status->flags |= TCFLAGS_CAPTURE;
+      status->flags |= TCFLAGS_HANDLER;
     }
 
   /* Return the actual timeout is milliseconds */
@@ -440,7 +438,7 @@ static int sam34_getstatus(FAR struct timer_lowerhalf_s *lower,
   /* Get the time remaining until the timer expires (in microseconds) */
 
   elapsed = sam34_getreg(priv->base + SAM_TC_CV_OFFSET);
-  status->timeleft = (priv->timeout * elapsed) / (priv->clkticks + 1); /* TODO - check on this +1 */
+  status->timeleft = ((uint64_t)priv->timeout * elapsed) / (priv->clkticks + 1); /* TODO - check on this +1 */
 
   tcvdbg("  flags    : %08x\n", status->flags);
   tcvdbg("  timeout  : %d\n", status->timeout);
@@ -470,6 +468,12 @@ static int sam34_settimeout(FAR struct timer_lowerhalf_s *lower,
   FAR struct sam34_lowerhalf_s *priv = (FAR struct sam34_lowerhalf_s *)lower;
 
   DEBUGASSERT(priv);
+
+  if (priv->started)
+    {
+      return -EPERM;
+    }
+
   tcvdbg("Entry: timeout=%d\n", timeout);
 
   /* Can this timeout be represented? */
@@ -486,21 +490,17 @@ static int sam34_settimeout(FAR struct timer_lowerhalf_s *lower,
   timeout = (1000000ULL * priv->clkticks) / TC_FCLK;          /* Truncated timeout */
   priv->adjustment = priv->timeout - timeout;                 /* Truncated time to be added to next interval (dither) */
 
-  tcvdbg("fwdt=%d reload=%d timout=%d, adjustment=%d\n",
-         TC_FCLK, reload, priv->timeout, priv->adjustment);
-
-  /* Don't commit to MR register until started! */
+  tcvdbg("fclk=%d clkticks=%d timout=%d, adjustment=%d\n",
+         TC_FCLK, priv->clkticks, priv->timeout, priv->adjustment);
 
   return OK;
 }
 
 /****************************************************************************
- * Name: sam34_capture
+ * Name: sam34_sethandler
  *
  * Description:
- *   Don't reset on timer timeout; instead, call this user provider
- *   timeout handler.  NOTE:  Providing handler==NULL will restore the reset
- *   behavior.
+ *   Call this user provided timeout handler.
  *
  * Input Parameters:
  *   lower      - A pointer the publicly visible representation of the "lower-half"
@@ -511,13 +511,12 @@ static int sam34_settimeout(FAR struct timer_lowerhalf_s *lower,
  *
  * Returned Values:
  *   The previous timer expiration function pointer or NULL is there was
- *   no previous function pointer, i.e., if the previous behavior was
- *   reset-on-expiration (NULL is also returned if an error occurs).
+ *   no previous function pointer.
  *
  ****************************************************************************/
 
-static tccb_t sam34_capture(FAR struct timer_lowerhalf_s *lower,
-                            tccb_t handler)
+static tccb_t sam34_sethandler(FAR struct timer_lowerhalf_s *lower,
+                               tccb_t handler)
 {
   FAR struct sam34_lowerhalf_s *priv = (FAR struct sam34_lowerhalf_s *)lower;
   irqstate_t flags;