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>
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@ -31,9 +31,9 @@
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(SDRAM_BASE_ADDR | SDRAM_BANK_SEL_##bank | SDRAM_MODE_REG_VAL))
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(SDRAM_BASE_ADDR | SDRAM_BANK_SEL_##bank | SDRAM_MODE_REG_VAL))
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#define PRECHARGE_BANK(bank) (*(volatile uint32_t *) \
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#define PRECHARGE_BANK(bank) (*(volatile uint32_t *) \
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(SDRAM_BASE_ADDR | SDRAM_BANK_SEL_##bank))
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(SDRAM_BASE_ADDR | SDRAM_BANK_SEL_##bank)) = 0
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static void force_precharge(void);
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static void precharge_all_banks(void);
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static void setup_refresh_timer(void);
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static void setup_refresh_timer(void);
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static void program_mode_registers(void);
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static void program_mode_registers(void);
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@ -48,7 +48,7 @@ void sdram_cfg(void)
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early_udelay(200);
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early_udelay(200);
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force_precharge();
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precharge_all_banks();
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setup_refresh_timer();
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setup_refresh_timer();
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@ -58,13 +58,22 @@ void sdram_cfg(void)
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writel(GLCONFIG_CKE, &sdram->glconfig);
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writel(GLCONFIG_CKE, &sdram->glconfig);
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}
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}
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static void force_precharge(void)
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static void precharge_all_banks(void)
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{
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{
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struct sdram_regs *sdram = (struct sdram_regs *)SDRAM_BASE;
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/* Issue PRECHARGE ALL commands */
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writel(GLCONFIG_INIT | GLCONFIG_CKE, &sdram->glconfig);
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/*
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/*
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* Errata most EP93xx revisions say that PRECHARGE ALL isn't always
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* Errata of most EP93xx revisions say that PRECHARGE ALL isn't always
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* issued.
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* issued.
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*
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*
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* Do a read from each bank to make sure they're precharged
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* Cirrus proposes a workaround which consists in performing a read from
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* each bank to force the precharge. This causes some boards to hang.
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* Writing to the SDRAM banks instead of reading has the same
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* side-effect (the SDRAM controller issues the necessary precharges),
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* but is known to work on all supported boards
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*/
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*/
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PRECHARGE_BANK(0);
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PRECHARGE_BANK(0);
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