speed.c

U-boot源码 ARM7启动代码

/*
 *
 * (C) Copyright 2000-2003
 * Wolfgang Denk, DENX Software Engineering, [e-mail].
 *
 * Copyright (C) 2004-2007 Freescale Semiconductor, Inc.
 * TsiChung Liew ([e-mail])
 *
 * See file CREDITS for list of people who contributed to this
 * project.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of
 * the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
 * MA 02111-1307 USA
 */

#include <common.h>
#include <asm/processor.h>

#include <asm/immap.h>

DECLARE_GLOBAL_DATA_PTR;

/* PLL min/max specifications */
#define MAX_FVCO	500000	/* KHz */
#define MAX_FSYS	80000	/* KHz */
#define MIN_FSYS	58333	/* KHz */
#define FREF		16000	/* KHz */
#define MAX_MFD		135	/* Multiplier */
#define MIN_MFD		88	/* Multiplier */
#define BUSDIV		6	/* Divider */
/*
 * Low Power Divider specifications
 */
#define MIN_LPD		(1 << 0)	/* Divider (not encoded) */
#define MAX_LPD		(1 << 15)	/* Divider (not encoded) */
#define DEFAULT_LPD	(1 << 1)	/* Divider (not encoded) */

/*
 * Get the value of the current system clock
 *
 * Parameters:
 *  none
 *
 * Return Value:
 *  The current output system frequency
 */
int get_sys_clock(void)
{
	volatile ccm_t *ccm = (volatile ccm_t *)(MMAP_CCM);
	volatile pll_t *pll = (volatile pll_t *)(MMAP_PLL);
	int divider;

	/* Test to see if device is in LIMP mode */
	if (ccm->misccr & CCM_MISCCR_LIMP) {
		divider = ccm->cdr & CCM_CDR_LPDIV(0xF);
		return (FREF / (2 << divider));
	} else {
		return ((FREF * pll->pfdr) / (BUSDIV * 4));
	}
}

/*
 * Initialize the Low Power Divider circuit
 *
 * Parameters:
 *  div     Desired system frequency divider
 *
 * Return Value:
 *  The resulting output system frequency
 */
int clock_limp(int div)
{
	volatile ccm_t *ccm = (volatile ccm_t *)(MMAP_CCM);
	u32 temp;

	/* Check bounds of divider */
	if (div < MIN_LPD)
		div = MIN_LPD;
	if (div > MAX_LPD)
		div = MAX_LPD;

	/* Save of the current value of the SSIDIV so we don't overwrite the value */
	temp = (ccm->cdr & CCM_CDR_SSIDIV(0xF));

	/* Apply the divider to the system clock */
	ccm->cdr = (CCM_CDR_LPDIV(div) | CCM_CDR_SSIDIV(temp));

	ccm->misccr |= CCM_MISCCR_LIMP;

	return (FREF / (3 * (1 << div)));
}

/*
 * Exit low power LIMP mode
 *
 * Parameters:
 *  div     Desired system frequency divider
 *
 * Return Value:
 *  The resulting output system frequency
 */
int clock_exit_limp(void)
{
	volatile ccm_t *ccm = (volatile ccm_t *)(MMAP_CCM);
	int fout;

	/* Exit LIMP mode */
	ccm->misccr &= (~CCM_MISCCR_LIMP);

	/* Wait for PLL to lock */
	while (!(ccm->misccr & CCM_MISCCR_PLL_LOCK)) ;

	fout = get_sys_clock();

	return fout;
}

/* Initialize the PLL
 *
 * Parameters:
 *  fref    PLL reference clock frequency in KHz
 *  fsys    Desired PLL output frequency in KHz
 *  flags   Operating parameters
 *
 * Return Value:
 *  The resulting output system frequency
 */
int clock_pll(int fsys, int flags)
{
	volatile u32 *sdram_workaround = (volatile u32 *)(MMAP_SDRAM + 0x80);
	volatile pll_t *pll = (volatile pll_t *)(MMAP_PLL);
	int fref, temp, fout, mfd;
	u32 i;

	fref = FREF;

	if (fsys == 0) {
		/* Return current PLL output */
		mfd = pll->pfdr;

		return (fref * mfd / (BUSDIV * 4));
	}

	/* Check bounds of requested system clock */
	if (fsys > MAX_FSYS)
		fsys = MAX_FSYS;

	if (fsys < MIN_FSYS)
		fsys = MIN_FSYS;

	/* Multiplying by 100 when calculating the temp value,
	   and then dividing by 100 to calculate the mfd allows
	   for exact values without needing to include floating
	   point libraries. */
	temp = (100 * fsys) / fref;
	mfd = (4 * BUSDIV * temp) / 100;

	/* Determine the output frequency for selected values */
	fout = ((fref * mfd) / (BUSDIV * 4));

	/*
	 * Check to see if the SDRAM has already been initialized.
	 * If it has then the SDRAM needs to be put into self refresh
	 * mode before reprogramming the PLL.
	 */

	/*
	 * Initialize the PLL to generate the new system clock frequency.
	 * The device must be put into LIMP mode to reprogram the PLL.
	 */

	/* Enter LIMP mode */
	clock_limp(DEFAULT_LPD);

	/* Reprogram PLL for desired fsys */
	pll->podr = (PLL_PODR_CPUDIV(BUSDIV / 3) | PLL_PODR_BUSDIV(BUSDIV));

	pll->pfdr = mfd;

	/* Exit LIMP mode */
	clock_exit_limp();

	/*
	 * Return the SDRAM to normal operation if it is in use.
	 */

	/* software workaround for SDRAM opeartion after exiting LIMP mode errata */
	*sdram_workaround = CFG_SDRAM_BASE;

	/* wait for DQS logic to relock */
	for (i = 0; i < 0x200; i++) ;

	return fout;
}

/*
 * get_clocks() fills in gd->cpu_clock and gd->bus_clk
 */
int get_clocks(void)
{
	gd->bus_clk = clock_pll(CFG_CLK / 1000, 0) * 1000;
	gd->cpu_clk = (gd->bus_clk * 3);
	return (0);
}