[PATCH] mmc: fsl_esdhc_imx: optimize the timing setting

[Jaehoon Chung]

On 11/3/20 6:18 PM, haibo.chen at nxp.com wrote:
> From: Haibo Chen <haibo.chen at nxp.com>
> 
> For imx usdhc/esdhc, once set the DDR_EN, enable the DDR mode, the
> card clock will be divied by 2 automatically by the host. So need
> to first config the DDR_EN correctly, then update the card clock.
> This will make sure the actual card clock is as our expected.
> IC also suggest config the DDR_EN firstly, then config the clock
> divider.
> 
> For HS400/HS400ES mode, need to config the strobe dll, this need
> to based on the correct target clock rate, so need to do this after
> clock rate is update.
> 
> Signed-off-by: Haibo Chen <haibo.chen at nxp.com>

Reviewed-by: Jaehoon Chung <jh80.chung at samsung.com>

Best Regards,
Jaehoon Chung

> ---
>  drivers/mmc/fsl_esdhc_imx.c | 32 ++++++++++++++++++++++++--------
>  1 file changed, 24 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/mmc/fsl_esdhc_imx.c b/drivers/mmc/fsl_esdhc_imx.c
> index 3843d61d71..98bc81f2de 100644
> --- a/drivers/mmc/fsl_esdhc_imx.c
> +++ b/drivers/mmc/fsl_esdhc_imx.c
> @@ -760,7 +760,6 @@ static int esdhc_set_timing(struct mmc *mmc)
>  	case MMC_HS_400_ES:
>  		mixctrl |= MIX_CTRL_DDREN | MIX_CTRL_HS400_EN;
>  		esdhc_write32(&regs->mixctrl, mixctrl);
> -		esdhc_set_strobe_dll(mmc);
>  		break;
>  	case MMC_HS:
>  	case MMC_HS_52:
> @@ -933,6 +932,23 @@ static int esdhc_set_ios_common(struct fsl_esdhc_priv *priv, struct mmc *mmc)
>  	int ret __maybe_unused;
>  	u32 clock;
>  
> +#ifdef MMC_SUPPORTS_TUNING
> +	/*
> +	 * call esdhc_set_timing() before update the clock rate,
> +	 * This is because current we support DDR and SDR mode,
> +	 * Once the DDR_EN bit is set, the card clock will be
> +	 * divide by 2 automatically. So need to do this before
> +	 * setting clock rate.
> +	 */
> +	if (priv->mode != mmc->selected_mode) {
> +		ret = esdhc_set_timing(mmc);
> +		if (ret) {
> +			printf("esdhc_set_timing error %d\n", ret);
> +			return ret;
> +		}
> +	}
> +#endif
> +
>  	/* Set the clock speed */
>  	clock = mmc->clock;
>  	if (clock < mmc->cfg->f_min)
> @@ -957,13 +973,13 @@ static int esdhc_set_ios_common(struct fsl_esdhc_priv *priv, struct mmc *mmc)
>  #endif
>  	}
>  
> -	if (priv->mode != mmc->selected_mode) {
> -		ret = esdhc_set_timing(mmc);
> -		if (ret) {
> -			printf("esdhc_set_timing error %d\n", ret);
> -			return ret;
> -		}
> -	}
> +	/*
> +	 * For HS400/HS400ES mode, make sure set the strobe dll in the
> +	 * target clock rate. So call esdhc_set_strobe_dll() after the
> +	 * clock updated.
> +	 */
> +	if (mmc->selected_mode == MMC_HS_400 || mmc->selected_mode == MMC_HS_400_ES)
> +		esdhc_set_strobe_dll(mmc);
>  
>  	if (priv->signal_voltage != mmc->signal_voltage) {
>  		ret = esdhc_set_voltage(mmc);
>