Re: [PATCH v2 1/2] mmc: sdhci_am654: Add retry tuning

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

On 21/08/24 22:24, Judith Mendez wrote:
> Add retry tuning up to 10 times if we fail to find
> a failing region or no passing itapdly. This is
> necessary since some eMMC has been observed to never
> find a failing itapdly on the first couple of tuning
> iterations, but eventually does. It has been observed that
> the tuning algorithm does not need to loop more than 10
> times before finding a failing itapdly.
> 
> Signed-off-by: Judith Mendez <jm@ti.com>

Seems to have compile errors. Looks like 'dev' lines belong in
next patch.

drivers/mmc/host/sdhci_am654.c: In function ‘sdhci_am654_calculate_itap’:
drivers/mmc/host/sdhci_am654.c:453:24: error: unused variable ‘dev’ [-Werror=unused-variable]
  453 |         struct device *dev = mmc_dev(host->mmc);
      |                        ^~~
drivers/mmc/host/sdhci_am654.c: In function ‘sdhci_am654_do_tuning’:
drivers/mmc/host/sdhci_am654.c:508:24: error: unused variable ‘dev’ [-Werror=unused-variable]
  508 |         struct device *dev = mmc_dev(host->mmc);
      |                        ^~~
drivers/mmc/host/sdhci_am654.c: In function ‘sdhci_am654_platform_execute_tuning’:
drivers/mmc/host/sdhci_am654.c:553:24: error: unused variable ‘dev’ [-Werror=unused-variable]
  553 |         struct device *dev = mmc_dev(host->mmc);
      |                        ^~~
cc1: all warnings being treated as errors

> ---
> Changes since v1:
> - Change logic in patch 1/2 from using recursive aproach
>   to calling a function iteratively for retuning
> ---
>  drivers/mmc/host/sdhci_am654.c | 54 ++++++++++++++++++++++++++--------
>  1 file changed, 42 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci_am654.c b/drivers/mmc/host/sdhci_am654.c
> index 64e10f7c9faa3..612f29fd7dfef 100644
> --- a/drivers/mmc/host/sdhci_am654.c
> +++ b/drivers/mmc/host/sdhci_am654.c
> @@ -86,6 +86,7 @@
>  
>  #define CLOCK_TOO_SLOW_HZ	50000000
>  #define SDHCI_AM654_AUTOSUSPEND_DELAY	-1
> +#define RETRY_TUNING_MAX	10
>  
>  /* Command Queue Host Controller Interface Base address */
>  #define SDHCI_AM654_CQE_BASE_ADDR 0x200
> @@ -151,6 +152,7 @@ struct sdhci_am654_data {
>  	u32 flags;
>  	u32 quirks;
>  	bool dll_enable;
> +	u32 tuning_loop;

Could use a comment explaining tuning_loop usage.

>  
>  #define SDHCI_AM654_QUIRK_FORCE_CDTEST BIT(0)
>  };
> @@ -453,12 +455,14 @@ static u32 sdhci_am654_calculate_itap(struct sdhci_host *host, struct window
>  	int prev_fail_end = -1;
>  	u8 i;
>  
> -	if (!num_fails)
> -		return ITAPDLY_LAST_INDEX >> 1;
> +	if (!num_fails) {
> +		/* Retry tuning */
> +		return -1;
> +	}
>  
>  	if (fail_window->length == ITAPDLY_LENGTH) {
> -		dev_err(dev, "No passing ITAPDLY, return 0\n");
> -		return 0;
> +		/* Retry tuning */
> +		return -1;
>  	}
>  
>  	first_fail_start = fail_window->start;
> @@ -494,16 +498,18 @@ static u32 sdhci_am654_calculate_itap(struct sdhci_host *host, struct window
>  	return (itap > ITAPDLY_LAST_INDEX) ? ITAPDLY_LAST_INDEX >> 1 : itap;
>  }
>  
> -static int sdhci_am654_platform_execute_tuning(struct sdhci_host *host,
> -					       u32 opcode)
> +static int sdhci_am654_do_tuning(struct sdhci_host *host,
> +				 u32 opcode)
>  {
>  	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
>  	struct sdhci_am654_data *sdhci_am654 = sdhci_pltfm_priv(pltfm_host);
>  	unsigned char timing = host->mmc->ios.timing;
>  	struct window fail_window[ITAPDLY_LENGTH];
> +	struct device *dev = mmc_dev(host->mmc);
>  	u8 curr_pass, itap;
>  	u8 fail_index = 0;
>  	u8 prev_pass = 1;
> +	int ret = 0;
>  
>  	memset(fail_window, 0, sizeof(fail_window));
>  
> @@ -532,15 +538,38 @@ static int sdhci_am654_platform_execute_tuning(struct sdhci_host *host,
>  	if (fail_window[fail_index].length != 0)
>  		fail_index++;
>  
> -	itap = sdhci_am654_calculate_itap(host, fail_window, fail_index,
> -					  sdhci_am654->dll_enable);
> +	ret = sdhci_am654_calculate_itap(host, fail_window, fail_index,
> +					 sdhci_am654->dll_enable);
>  
> -	sdhci_am654_write_itapdly(sdhci_am654, itap, sdhci_am654->itap_del_ena[timing]);
> +	return ret;

Kernel style is to return directly i.e.

	return sdhci_am654_calculate_itap(host, fail_window, fail_index, sdhci_am654->dll_enable);

then don't need ret.

> +}
>  
> -	/* Save ITAPDLY */
> -	sdhci_am654->itap_del_sel[timing] = itap;
> +static int sdhci_am654_platform_execute_tuning(struct sdhci_host *host,
> +					       u32 opcode)
> +{
> +	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> +	struct sdhci_am654_data *sdhci_am654 = sdhci_pltfm_priv(pltfm_host);
> +	unsigned char timing = host->mmc->ios.timing;
> +	struct device *dev = mmc_dev(host->mmc);
> +	int itapdly;
> +	int ret = 0;
>  
> -	return 0;
> +	itapdly = sdhci_am654_do_tuning(host, opcode);
> +
> +	while (sdhci_am654->tuning_loop < RETRY_TUNING_MAX && itapdly < 0) {
> +		sdhci_am654->tuning_loop++;
> +		itapdly = sdhci_am654_do_tuning(host, opcode);
> +	}

Better to try to have sdhci_am654_do_tuning() appear only once
e.g. something like:

	do {
		itapdly = sdhci_am654_do_tuning(host, opcode);
		if (itapdly >= 0)
			break;
	} while (++sdhci_am654->tuning_loop < RETRY_TUNING_MAX);


> +
> +	if (itapdly >= 0) {
> +		sdhci_am654_write_itapdly(sdhci_am654, itapdly, sdhci_am654->itap_del_ena[timing]);
> +		/* Save ITAPDLY */
> +		sdhci_am654->itap_del_sel[timing] = itapdly;
> +	} else {
> +		ret = -1;
> +	}

It is easier to read if the error path is separate e.g.

	if (itapdly < 0)
		return -1;

	sdhci_am654_write_itapdly(sdhci_am654, itapdly, sdhci_am654->itap_del_ena[timing]);
	/* Save ITAPDLY */
	sdhci_am654->itap_del_sel[timing] = itapdly;

	return 0;

Doesn't need ret then either.

> +
> +	return ret;
>  }
>  
>  static const struct sdhci_ops sdhci_am654_ops = {
> @@ -908,6 +937,7 @@ static int sdhci_am654_probe(struct platform_device *pdev)
>  		goto err_pltfm_free;
>  	}
>  
> +	sdhci_am654->tuning_loop = 0;

It is a bit arbitrary having this at probe time.  Something like
putting it in an mmc card_init callback might make more sense?

>  	host->mmc_host_ops.execute_tuning = sdhci_am654_execute_tuning;
>  
>  	pm_runtime_get_noresume(dev);