sdramc.c

针对at91系列的arm的启动代码的编写有一个整体的说明

/* ----------------------------------------------------------------------------
 *         ATMEL Microcontroller Software Support  -  ROUSSET  -
 * ----------------------------------------------------------------------------
 * Copyright (c) 2006, Atmel Corporation

 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * - Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the disclaiimer below.
 *
 * - Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the disclaimer below in the documentation and/or
 * other materials provided with the distribution.
 *
 * Atmel's name may not be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * DISCLAIMER: THIS SOFTWARE IS PROVIDED BY ATMEL "AS IS" AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT ARE
 * DISCLAIMED. IN NO EVENT SHALL ATMEL 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.
 * ----------------------------------------------------------------------------
 * File Name           : sdramc.c
 * Object              :
 * Creation            : NLe Jul 11th 2006
 *-----------------------------------------------------------------------------
 */
#include "../include/sdramc.h"
#include "../include/part.h"
#include "../include/main.h"

#ifdef CFG_SDRAM

/* Write SDRAMC register */
static inline void write_sdramc(unsigned int offset, const unsigned int value)
{
	writel(value, offset + AT91C_BASE_SDRAMC);
}

/* Read SDRAMC registers */
static inline unsigned int read_sdramc(unsigned int offset)
{
	return readl(offset + AT91C_BASE_SDRAMC);
}

//*----------------------------------------------------------------------------
//* \fn    sdram_init
//* \brief Initialize the SDRAM Controller
//*----------------------------------------------------------------------------
int sdram_init(unsigned int sdramc_cr, unsigned int sdramc_tr)
{
	volatile unsigned int i;

	/* Performs the hardware initialization */
	sdramc_hw_init();

	/* CFG Control Register */
	write_sdramc(SDRAMC_CR, sdramc_cr);

	for (i =0; i< 1000;i++);

	write_sdramc(SDRAMC_MR, AT91C_SDRAMC_MODE_PRCGALL_CMD);	// Set PRCHG AL
	writel(0x00000000, AT91C_SDRAM);						// Perform PRCHG

	for (i =0; i< 10000;i++);

	write_sdramc(SDRAMC_MR, AT91C_SDRAMC_MODE_RFSH_CMD);	// Set 1st CBR
	writel(0x00000001, AT91C_SDRAM+4);						// Perform CBR

	write_sdramc(SDRAMC_MR, AT91C_SDRAMC_MODE_RFSH_CMD);	// Set 2 CBR
	writel(0x00000002, AT91C_SDRAM+8);						// Perform CBR

	write_sdramc(SDRAMC_MR, AT91C_SDRAMC_MODE_RFSH_CMD);	// Set 3 CBR
	writel(0x00000003, AT91C_SDRAM+0xc);					// Perform CBR

	write_sdramc(SDRAMC_MR, AT91C_SDRAMC_MODE_RFSH_CMD);	// Set 4 CBR
	writel(0x00000004, AT91C_SDRAM+0x10);					// Perform CBR

	write_sdramc(SDRAMC_MR, AT91C_SDRAMC_MODE_RFSH_CMD);	// Set 5 CBR
	writel(0x00000005, AT91C_SDRAM+0x14);					// Perform CBR

	write_sdramc(SDRAMC_MR, AT91C_SDRAMC_MODE_RFSH_CMD);	// Set 6 CBR
	writel(0x00000006, AT91C_SDRAM+0x18);					// Perform CBR

	write_sdramc(SDRAMC_MR, AT91C_SDRAMC_MODE_RFSH_CMD);	// Set 7 CBR
	writel(0x00000007, AT91C_SDRAM+0x1C);					// Perform CBR

	write_sdramc(SDRAMC_MR, AT91C_SDRAMC_MODE_RFSH_CMD);	// Set 8 CBR
	writel(0x00000008, AT91C_SDRAM+0x20);					// Perform CBR

	write_sdramc(SDRAMC_MR, AT91C_SDRAMC_MODE_LMR_CMD);		// Set LMR operation
	writel(0xcafedede, AT91C_SDRAM+0x24);					// Perform LMR burst=1, lat=2

	write_sdramc(SDRAMC_TR, sdramc_tr);						// Set Refresh Timer

	write_sdramc(SDRAMC_MR, AT91C_SDRAMC_MODE_NORMAL_CMD);	// Set Normal mode
	writel(0x00000000, AT91C_SDRAM);						// Perform Normal mode

	return 0;
}

#endif /* CFG_SDRAM */