Re: [PATCH v2 03/11] ARM: at91: Add initialize function to sdramc

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

On 28.06.22 22:38, Sam Ravnborg wrote:
> Port the sdramc initialize function from at91bootstrap.
> It is needed from lowlevel code and is a replacement for the
> sdramc init code in at91sam926x_board_init.h
> 
> Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

Reviewed-by: Ahmad Fatoum <a.fatoum@pengutronix.de>

> +int at91sam9_sdramc_initialize(const struct at91sam9_sdramc_config *config,
> +			       unsigned int sdram_address)
> +{
> +	unsigned int i;
> +
> +	/* Step#1 SDRAM feature must be in the configuration register */
> +	sdramc_wr(config, AT91_SDRAMC_CR, config->cr);
> +
> +	/* Step#2 For mobile SDRAM, temperature-compensated self refresh(TCSR),... */
> +
> +	/* Step#3 The SDRAM memory type must be set in the Memory Device Register */
> +	sdramc_wr(config, AT91_SDRAMC_MDR, config->mdr);
> +
> +	/* Step#4 The minimum pause of 200 us is provided to precede any single toggle */
> +	early_udelay(200);
> +
> +	/* Step#5 A NOP command is issued to the SDRAM devices */
> +	sdramc_wr(config, AT91_SDRAMC_MR, AT91_SDRAMC_MODE_NOP);
> +	writel(0x00000000, sdram_address);
> +
> +	/* Step#6 An All Banks Precharge command is issued to the SDRAM devices  */
> +	sdramc_wr(config, AT91_SDRAMC_MR, AT91_SDRAMC_MODE_PRECHARGE);
> +	writel(0x00000000, sdram_address);
> +
> +	/* Pause cycles */
> +	early_udelay(2000);
> +
> +	/* Step#7 Eight auto-refresh cycles are provided */
> +	for (i = 0; i < 8; i++) {
> +		sdramc_wr(config, AT91_SDRAMC_MR, AT91_SDRAMC_MODE_REFRESH);
> +		writel(0x00000001 + i, sdram_address + 4 + 4 * i);
> +	}
> +
> +	/* Pause cycles */
> +	early_udelay(200);
> +
> +	/* Step#8 A Mode Register set (MRS) cycle is issued to program (TCSR, PASR, DS) */
> +	sdramc_wr(config, AT91_SDRAMC_MR, AT91_SDRAMC_MODE_LMR);
> +	writel(0xcafedede, sdram_address + 0x24);
> +
> +	/*  Pause cycles */
> +	early_udelay(200);
> +
> +	/* Step#9 For mobile SDRAM initialization, an Extended Mode Register set ... */
> +
> +	/* Step#10 The application must go into Normal Mode, setting Mode to 0
> +	 * and perform a write access at any location in the SDRAM.
> +	 */
> +	sdramc_wr(config, AT91_SDRAMC_MR, AT91_SDRAMC_MODE_NORMAL);	// Set mode
> +	writel(0x00000000, sdram_address);				// Perform mode
> +
> +	/* Step#11 Write the refresh rate into the count field in the Refresh Register. */
> +	sdramc_wr(config, AT91_SDRAMC_TR, config->tr);
> +
> +	return 0;

Nitpick: Function can be void if it always reports success.

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