diff --git a/arch/arm/src/lpc313x/Make.defs b/arch/arm/src/lpc313x/Make.defs
index 9d9a7dd49a5e09f9f8d36e36e9e3d15a7af6a964..2eee54cc8e870789a9b5811633f53924873f74e4 100755
--- a/arch/arm/src/lpc313x/Make.defs
+++ b/arch/arm/src/lpc313x/Make.defs
@@ -46,7 +46,8 @@ CMN_CSRCS = up_assert.c up_blocktask.c up_copystate.c up_createstack.c \
up_undefinedinsn.c up_usestack.c
CGU_ASRCS =
-CGU_CSRCS = lpc313x_clkdomain.c lpc313x_fdcndx.c lpc313x_esrndx.c
+CGU_CSRCS = lpc313x_clkdomain.c lpc313x_clkfreq.c lpc313x_esrndx.c \
+ lpc313x_fdcndx.c
CHIP_ASRCS = $(CGU_ASRCS)
CHIP_CSRCS = lpc313x_irq.c lpc313x_allocateheap.c $(CGU_CSRCS)
diff --git a/arch/arm/src/lpc313x/lpc313x_cgu.h b/arch/arm/src/lpc313x/lpc313x_cgu.h
index 4733a2605198fdf689123d1ed841ca9bd7399949..3d31fe4b67b9c651226023f6869139e2b5511a0a 100755
--- a/arch/arm/src/lpc313x/lpc313x_cgu.h
+++ b/arch/arm/src/lpc313x/lpc313x_cgu.h
@@ -1197,7 +1197,7 @@
#define CGU_FDC_MSUB_SHIFT (11) /* Bits 11-18: Modulo subtraction value */
#define CGU_FDC_MSUB_MASK (255 << CGU_FDC_MSUB_SHIFT)
-#define CGU_FDC_MADD_SHIFT (3) /* Bits 3-10: Modulo addition value */
+#define CGU_FDC_MADD_SHIFT (3) /* Bits 3-10: Modulo addition value */
#define CGU_FDC_MADD_MASK (255 << CGU_FDC_MADD_SHIFT)
#define CGU_FDC_STRETCH (1 << 2) /* Bit 2: Enables the stretching option */
#define CGU_FDC_RESET (1 << 1) /* Bit 1: Reset fractional divider */
@@ -1205,7 +1205,7 @@
#define CGU_FDC17_MSUB_SHIFT (16) /* Bits 16-28: Modulo subtraction value */
#define CGU_FDC17_MSUB_MASK (0x1fff << CGU_FDC17_MSUB_SHIFT)
-#define CGU_FDC17_MADD_SHIFT (3) /* Bits 3-15: Modulo addition value */
+#define CGU_FDC17_MADD_SHIFT (3) /* Bits 3-15: Modulo addition value */
#define CGU_FDC17_MADD_MASK (0x1fff << CGU_FDC17_MADD_SHIFT)
#define CGU_FDC17_STRETCH (1 << 2) /* Bit 2: Enables the stretching option */
#define CGU_FDC17_RESET (1 << 1) /* Bit 1: Reset fractional divider */
diff --git a/arch/arm/src/lpc313x/lpc313x_cgudrvr.h b/arch/arm/src/lpc313x/lpc313x_cgudrvr.h
index 0fb105c8d2fdf3999846d73ad43b7e006a480104..5d3089191ae6cc06980a30b730419737ba02801f 100755
--- a/arch/arm/src/lpc313x/lpc313x_cgudrvr.h
+++ b/arch/arm/src/lpc313x/lpc313x_cgudrvr.h
@@ -457,6 +457,18 @@ EXTERN int lp313x_esrndx(enum lpc313x_clockid_e clkid);
EXTERN int lpc313x_fdcndx(enum lpc313x_clockid_e clkid,
enum lpc313x_domainid_e dmnid);
+/************************************************************************
+ * Name: lpc313x_fdcndx
+ *
+ * Description:
+ * Given a clock ID and its domain ID, return the frequency of the
+ * clock.
+ *
+ ************************************************************************/
+
+EXTERN uint32_t lpc313x_clkfreq(enum lpc313x_clockid_e clkid,
+ enum lpc313x_domainid_e dmnid);
+
#undef EXTERN
#ifdef __cplusplus
}
diff --git a/arch/arm/src/lpc313x/lpc313x_clkfreq.c b/arch/arm/src/lpc313x/lpc313x_clkfreq.c
new file mode 100755
index 0000000000000000000000000000000000000000..8d4f9fb35f90b3b985b5fa0ebaa05a9f7185957d
--- /dev/null
+++ b/arch/arm/src/lpc313x/lpc313x_clkfreq.c
@@ -0,0 +1,177 @@
+/************************************************************************
+ * arch/arm/src/lpc313x/lpc313x_clkfreq.c
+ *
+ * Copyright (C) 2009 Gregory Nutt. All rights reserved.
+ * Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * References:
+ * - UM10314 LPC3130/31 User manual Rev. 1.01 � 9 September 2009
+ * - lpc313x.cdl.drivers.zip example driver code
+ *
+ * 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 <stdint.h>
+
+#include "up_arch.h"
+#include "lpc313x_cgudrvr.h"
+
+/************************************************************************
+ * Pre-processor Definitions
+ ************************************************************************/
+
+/************************************************************************
+ * Private Data
+ ************************************************************************/
+
+/************************************************************************
+ * Private Functions
+ ************************************************************************/
+
+/************************************************************************
+ * Public Functions
+ ************************************************************************/
+
+/************************************************************************
+ * Name: lpc313x_fdcndx
+ *
+ * Description:
+ * Given a clock ID and its domain ID, return the frequency of the
+ * clock.
+ *
+ ************************************************************************/
+
+uint32_t lpc313x_clkfreq(enum lpc313x_clockid_e clkid,
+ enum lpc313x_domainid_e dmnid)
+{
+ uint32_t freq = 0;
+ uint32_t fdcndx;
+ uint32_t regval;
+
+ /* Get then fractional divider register index for this clock */
+
+ fdcndx = lpc313x_fdcndx(clkid, dmnid);
+
+ /* Get base frequency for the domain */
+
+ freq = lpc313x_basefreq(dmnid);
+
+ /* If there is no fractional divider associated with the clodk, then the
+ * connection is directo and we just return the base frequency.
+ */
+
+ if (fdcndx == FDCNDX_INVALID)
+ {
+ return freq;
+ }
+
+ /* Read fractional divider control (FDC) register value and double check that
+ * it is enabled (not necessary since lpc313x_fdcndx() also does this check
+ */
+
+ regval = getreg32(LPC313X_CGU_FDC_OFFSET(fdcndx));
+ if ((regval & CGU_ESR_ESREN) != 0)
+ {
+ int32_t msub;
+ int32_t madd;
+ int32_t n;
+ int32_t m;
+
+ /* Yes, extract modulo subtraction and addition values, msub and madd.
+ * Fractional divider 17 is a special case because its msub and madd
+ * fields have greater range.
+ */
+
+ if (fdcndx == 17)
+ {
+ /* Range is 0-0x1fff for both */
+
+ msub = (regval & CGU_FDC17_MSUB_MASK) >> CGU_FDC17_MSUB_SHIFT;
+ madd = (regval & CGU_FDC17_MADD_MASK) >> CGU_FDC17_MADD_SHIFT;
+ }
+ else
+ {
+ /* Range is 0-255 for both */
+
+ msub = (regval & CGU_FDC_MSUB_MASK) >> CGU_FDC_MSUB_SHIFT;
+ madd = (regval & CGU_FDC_MADD_MASK) >> CGU_FDC_MADD_SHIFT;
+ }
+
+ /* Handle a corner case that would result in an infinite loop below */
+
+ if (msub == 0 && madd == 0)
+ {
+ return 0;
+ }
+
+ /* Reduce to the greatest common power-of-2 denominator. To minimize
+ * power consumption, the lpc313x user manual recommends that madd and msub
+ * be shifted right to have as many trailing zero's as possible. The
+ * following undoes that shift.
+ */
+
+ while ((msub & 1) == 0 && (madd & 1) == 0)
+ {
+ madd = madd >> 1;
+ msub = msub >> 1;
+ }
+
+ /* Then compute n and m values:
+ *
+ * fout = n/m * fin
+ *
+ * where
+ *
+ * madd = m - n
+ * msub = -n
+ */
+
+ n = -msub;
+ m = madd + n;
+
+ /* Check that both m and n are non-zero values */
+
+ if ((n == 0) || (m == 0))
+ {
+ return 0;
+ }
+
+ /* Finally, calculate the frequency based on m and n values */
+
+ freq = (freq * n) / m ;
+ }
+
+ return freq;
+}
+