[U-Boot] [PATCH 1/4] mmc: fsl_esdhc: Allow all supported prescaler values

[Stefano Babic]

On 03/05/2017 11:59, Benoît Thébaudeau wrote:
> On i.MX, SYSCTL.SDCLKFS may be set to 0 in order to make the SD clock
> frequency prescaler divide by 1 in SDR mode. In DDR mode, the prescaler
> can divide by up to 512. Allow both of these settings.
> 
> The maximum SD clock frequency in High Speed mode is 50 MHz. On i.MX25,
> this change makes it possible to get 48 MHz from the USB PLL
> (240 MHz / 5 / 1) instead of only 40 MHz from the USB PLL
> (240 MHz / 3 / 2) or 33.25 MHz from the AHB clock (133 MHz / 2 / 2).
> 
> Signed-off-by: Benoît Thébaudeau <benoit at wsystem.com>
> ---
>  drivers/mmc/fsl_esdhc.c | 23 ++++++++++++-----------
>  1 file changed, 12 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/mmc/fsl_esdhc.c b/drivers/mmc/fsl_esdhc.c
> index f3c6358..ca72627 100644
> --- a/drivers/mmc/fsl_esdhc.c
> +++ b/drivers/mmc/fsl_esdhc.c
> @@ -521,7 +521,13 @@ out:
>  
>  static void set_sysctl(struct mmc *mmc, uint clock)
>  {
> -	int div, pre_div;
> +	int div = 1;
> +#ifdef ARCH_MXC
> +	int pre_div = 1;
> +#else
> +	int pre_div = 2;
> +#endif
> +	int ddr_pre_div = mmc->ddr_mode ? 2 : 1;
>  	struct fsl_esdhc_priv *priv = mmc->priv;
>  	struct fsl_esdhc *regs = priv->esdhc_regs;
>  	int sdhc_clk = priv->sdhc_clk;
> @@ -530,18 +536,13 @@ static void set_sysctl(struct mmc *mmc, uint clock)
>  	if (clock < mmc->cfg->f_min)
>  		clock = mmc->cfg->f_min;
>  
> -	if (sdhc_clk / 16 > clock) {
> -		for (pre_div = 2; pre_div < 256; pre_div *= 2)
> -			if ((sdhc_clk / pre_div) <= (clock * 16))
> -				break;
> -	} else
> -		pre_div = 2;
> +	while (sdhc_clk / (16 * pre_div * ddr_pre_div) > clock && pre_div < 256)
> +		pre_div *= 2;
>  
> -	for (div = 1; div <= 16; div++)
> -		if ((sdhc_clk / (div * pre_div)) <= clock)
> -			break;
> +	while (sdhc_clk / (div * pre_div * ddr_pre_div) > clock && div < 16)
> +		div++;
>  
> -	pre_div >>= mmc->ddr_mode ? 2 : 1;
> +	pre_div >>= 1;
>  	div -= 1;
>  
>  	clk = (pre_div << 8) | (div << 4);
> 

Applied to u-boot-imx -master, thanks !

Best regards,
Stefano Babic

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