Re: [PATCH] edb93xx: Fix SDRAM precharge

[Sascha Hauer <s.hauer@pengutronix.de>]

On Wed, Feb 24, 2010 at 08:08:07PM +0100, Matthias Kaehlcke wrote:
> 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

Ok, applied.

Sascha

> 
> Signed-off-by: Matthias Kaehlcke <matthias@kaehlcke.net>
> ---
>  board/edb93xx/sdram_cfg.c |   21 +++++++++++++++------
>  1 files changed, 15 insertions(+), 6 deletions(-)
> 
> diff --git a/board/edb93xx/sdram_cfg.c b/board/edb93xx/sdram_cfg.c
> index 25b214b..3d4fe08 100644
> --- a/board/edb93xx/sdram_cfg.c
> +++ b/board/edb93xx/sdram_cfg.c
> @@ -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);
> -- 
> 1.6.5
> 
> 
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