Re: [PATCH] mmc: sdhci-esdhc-imx: optimize the manual tuing logic to get the best timing

[Adrian Hunter <adrian.hunter@intel.com>]

On 31/08/23 06:26, haibo.chen@nxp.com wrote:
> From: Haibo Chen <haibo.chen@nxp.com>
> 
> Current manual tuning logic only get the first pass window, but
> this pass window maybe not the best pass window.
> 
> Now find all the pass window, and chose the largest pass window,
> and use the average value of this largest pass window to get the
> best timing.
> 
> Signed-off-by: Haibo Chen <haibo.chen@nxp.com>

Acked-by: Adrian Hunter <adrian.hunter@intel.com>

> ---
>  drivers/mmc/host/sdhci-esdhc-imx.c | 52 +++++++++++++++++++++---------
>  1 file changed, 36 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-esdhc-imx.c
> index 6170b7121f36..4cbbc0a786a0 100644
> --- a/drivers/mmc/host/sdhci-esdhc-imx.c
> +++ b/drivers/mmc/host/sdhci-esdhc-imx.c
> @@ -1154,32 +1154,52 @@ static void esdhc_post_tuning(struct sdhci_host *host)
>  	writel(reg, host->ioaddr + ESDHC_MIX_CTRL);
>  }
>  
> +/*
> + * find the largest pass window, and use the average delay of this
> + * largest window to get the best timing.
> + */
>  static int esdhc_executing_tuning(struct sdhci_host *host, u32 opcode)
>  {
>  	int min, max, avg, ret;
> +	int win_length, target_min, target_max, target_win_length;
>  
> -	/* find the mininum delay first which can pass tuning */
>  	min = ESDHC_TUNE_CTRL_MIN;
> -	while (min < ESDHC_TUNE_CTRL_MAX) {
> -		esdhc_prepare_tuning(host, min);
> -		if (!mmc_send_tuning(host->mmc, opcode, NULL))
> -			break;
> -		min += ESDHC_TUNE_CTRL_STEP;
> -	}
> -
> -	/* find the maxinum delay which can not pass tuning */
> -	max = min + ESDHC_TUNE_CTRL_STEP;
> +	max = ESDHC_TUNE_CTRL_MIN;
> +	target_win_length = 0;
>  	while (max < ESDHC_TUNE_CTRL_MAX) {
> -		esdhc_prepare_tuning(host, max);
> -		if (mmc_send_tuning(host->mmc, opcode, NULL)) {
> -			max -= ESDHC_TUNE_CTRL_STEP;
> -			break;
> +		/* find the mininum delay first which can pass tuning */
> +		while (min < ESDHC_TUNE_CTRL_MAX) {
> +			esdhc_prepare_tuning(host, min);
> +			if (!mmc_send_tuning(host->mmc, opcode, NULL))
> +				break;
> +			min += ESDHC_TUNE_CTRL_STEP;
>  		}
> -		max += ESDHC_TUNE_CTRL_STEP;
> +
> +		/* find the maxinum delay which can not pass tuning */
> +		max = min + ESDHC_TUNE_CTRL_STEP;
> +		while (max < ESDHC_TUNE_CTRL_MAX) {
> +			esdhc_prepare_tuning(host, max);
> +			if (mmc_send_tuning(host->mmc, opcode, NULL)) {
> +				max -= ESDHC_TUNE_CTRL_STEP;
> +				break;
> +			}
> +			max += ESDHC_TUNE_CTRL_STEP;
> +		}
> +
> +		win_length = max - min + 1;
> +		/* get the largest pass window */
> +		if (win_length > target_win_length) {
> +			target_win_length = win_length;
> +			target_min = min;
> +			target_max = max;
> +		}
> +
> +		/* continue to find the next pass window */
> +		min = max + ESDHC_TUNE_CTRL_STEP;
>  	}
>  
>  	/* use average delay to get the best timing */
> -	avg = (min + max) / 2;
> +	avg = (target_min + target_max) / 2;
>  	esdhc_prepare_tuning(host, avg);
>  	ret = mmc_send_tuning(host->mmc, opcode, NULL);
>  	esdhc_post_tuning(host);