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edb93xx: Fix SDRAM initialization

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edb93xx: Fix SDRAM initialization by issuing a precharge all command before
forcing the precharge and select mode register update mode before programming
the mode registers. Write to the SDRAM banks in order to force a precharge,
reading causes the edb93xx boards to hang

Signed-off-by: Matthias Kaehlcke <matthias@kaehlcke.net>
This commit is contained in:
Matthias Kaehlcke 2010-02-24 19:45:39 +01:00 • committed by Tom Rix
parent cade7d9577
commit 18ba012b9b
1 changed files with 31 additions and 8 deletions
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39
board/edb93xx/sdram_cfg.c
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@ -1,5 +1,5 @@
/*
* Copyright (C) 2009 Matthias Kaehlcke <matthias@kaehlcke.net>
* Copyright (C) 2009, 2010 Matthias Kaehlcke <matthias@kaehlcke.net>
*
* Copyright (C) 2006 Dominic Rath <Dominic.Rath@gmx.de>
*
@ -30,9 +30,9 @@
(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))
(SDRAM_BASE_ADDR | SDRAM_BANK_SEL_##bank)) = 0
static void force_precharge(void);
static void precharge_all_banks(void);
static void setup_refresh_timer(void);
static void program_mode_registers(void);
@ -47,7 +47,7 @@ void sdram_cfg(void)
early_udelay(200);
force_precharge();
precharge_all_banks();
setup_refresh_timer();
@ -57,19 +57,37 @@ void sdram_cfg(void)
writel(GLCONFIG_CKE, &sdram->glconfig);
}
static void force_precharge(void)
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 most EP93xx revisions say that PRECHARGE ALL isn't always
* issued.
* Errata of most EP93xx revisions say that PRECHARGE ALL isn't always
* issued
*
* Do a read from each bank to make sure they're precharged
* 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)
@ -101,6 +119,11 @@ static void setup_refresh_timer(void)
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