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/************************************************************************
* arch/arm/src/lpc31xx/lpc31_clkfreq.c
*
* Copyright (C) 2009-2010 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* 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 "lpc31_cgudrvr.h"
/************************************************************************
* Pre-processor Definitions
************************************************************************/
/************************************************************************
* Private Data
************************************************************************/
/************************************************************************
* Private Functions
************************************************************************/
/************************************************************************
* Public Functions
************************************************************************/
/************************************************************************
* Name: lpc31_fdcndx
*
* Description:
* Given a clock ID and its domain ID, return the frequency of the
* clock.
*
************************************************************************/
uint32_t lpc31_clkfreq(enum lpc31_clockid_e clkid,
enum lpc31_domainid_e dmnid)
{
uint32_t freq = 0;
uint32_t fdcndx;
uint32_t regval;
/* Get then fractional divider register index for this clock */
fdcndx = lpc31_fdcndx(clkid, dmnid);
/* Get base frequency for the domain */
freq = lpc31_getbasefreq(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 lpc31_fdcndx() also does this check
*/
regval = getreg32(LPC31_CGU_FDC(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) | CGU_FDC17_MSUB_EXTEND;
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) | CGU_FDC_MSUB_EXTEND;
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;
}
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