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/*
* Copyright (C) 2009, 2010 Matthias Kaehlcke <matthias@kaehlcke.net>
*
* Copyright (C) 2006 Dominic Rath <Dominic.Rath@gmx.de>
*
* 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 <asm/io.h>
#include "sdram_cfg.h"
#include "early_udelay.h"
#define PROGRAM_MODE_REG(bank) (*(volatile uint32_t *) \
(SDRAM_BASE_ADDR | SDRAM_BANK_SEL_##bank | SDRAM_MODE_REG_VAL))
#define PRECHARGE_BANK(bank) (*(volatile uint32_t *) \
(SDRAM_BASE_ADDR | SDRAM_BANK_SEL_##bank)) = 0
static void precharge_all_banks(void);
static void setup_refresh_timer(void);
static void program_mode_registers(void);
void sdram_cfg(void)
{
struct sdram_regs *sdram = (struct sdram_regs *)SDRAM_BASE;
writel(SDRAM_DEVCFG_VAL, &sdram->SDRAM_DEVCFG_REG);
/* Issue continous NOP commands */
writel(GLCONFIG_INIT | GLCONFIG_MRS | GLCONFIG_CKE, &sdram->glconfig);
early_udelay(200);
precharge_all_banks();
setup_refresh_timer();
program_mode_registers();
/* Select normal operation mode */
writel(GLCONFIG_CKE, &sdram->glconfig);
}
static void precharge_all_banks(void)
{
struct sdram_regs *sdram = (struct sdram_regs *)SDRAM_BASE;
/* Issue PRECHARGE ALL commands */
writel(GLCONFIG_INIT | GLCONFIG_CKE, &sdram->glconfig);
/*
* Errata of most EP93xx revisions say that PRECHARGE ALL isn't always
* issued
*
* Cirrus proposes a workaround which consists in performing a read from
* each bank to force the precharge. This causes some boards to hang.
* Writing to the SDRAM banks instead of reading has the same
* side-effect (the SDRAM controller issues the necessary precharges),
* but is known to work on all supported boards
*/
PRECHARGE_BANK(0);
#if (CONFIG_NR_DRAM_BANKS >= 2)
PRECHARGE_BANK(1);
#endif
#if (CONFIG_NR_DRAM_BANKS >= 3)
PRECHARGE_BANK(2);
#endif
#if (CONFIG_NR_DRAM_BANKS == 4)
PRECHARGE_BANK(3);
#endif
}
static void setup_refresh_timer(void)
{
struct sdram_regs *sdram = (struct sdram_regs *)SDRAM_BASE;
/* Load refresh timer with 10 to issue refresh every 10 cycles */
writel(0x0a, &sdram->refrshtimr);
/*
* Wait at least 80 clock cycles to provide 8 refresh cycles
* to all SDRAMs
*/
early_udelay(1);
/*
* Program refresh timer with normal value
* We need 8192 refresh cycles every 64ms
* at 15ns (HCLK >= 66MHz) per cycle:
* 64ms / 8192 = 7.8125us
* 7.8125us / 15ns = 520 (0x208)
*/
/*
* TODO: redboot uses 0x1e0 for the slowest possible device
* but i don't understand how this value is calculated
*/
writel(0x208, &sdram->refrshtimr);
}
static void program_mode_registers(void)
{
struct sdram_regs *sdram = (struct sdram_regs *)SDRAM_BASE;
/* Select mode register update mode */
writel(GLCONFIG_MRS | GLCONFIG_CKE, &sdram->glconfig);
/*
* The mode registers are programmed by performing a read from each
* SDRAM bank. The value of the address that is read defines the value
* that is written into the mode register
*/
PROGRAM_MODE_REG(0);
#if (CONFIG_NR_DRAM_BANKS >= 2)
PROGRAM_MODE_REG(1);
#endif
#if (CONFIG_NR_DRAM_BANKS >= 3)
PROGRAM_MODE_REG(2);
#endif
#if (CONFIG_NR_DRAM_BANKS == 4)
PROGRAM_MODE_REG(3);
#endif
}
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