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edb93xx: Fix SDRAM precharge 

edb93xx SDRAM initialization: Issue a precharge all command before forcing the
precharge of all SDRAM banks. Write to the SDRAM in order to force a precharge,
reading causes the edb93xx boards to hang

Signed-off-by: Matthias Kaehlcke <matthias@kaehlcke.net>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
This commit is contained in:
Matthias Kaehlcke 2010-02-24 20:08:07 +01:00 committed by Sascha Hauer
parent 6351ff2eff
commit 53eaaf0f82
1 changed files with 15 additions and 6 deletions
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21
board/edb93xx/sdram_cfg.c
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@ -31,9 +31,9 @@
(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);
@ -48,7 +48,7 @@ void sdram_cfg(void)
early_udelay(200);
force_precharge();
precharge_all_banks();
setup_refresh_timer();
@ -58,13 +58,22 @@ 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
* 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);