[v3,1/2] mmc: sdhci_am654: Add retry tuning

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. Keep count of current
tuning iteration using tuning_loop. 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>
---
Changes since v2:
- Use do while loop instead of while in patch 1/2
- Move initialization of tuning_loop to sdhci_am654_init
- Separate error path in patch 1/2
---
 drivers/mmc/host/sdhci_am654.c | 46 ++++++++++++++++++++++++++--------
 1 file changed, 35 insertions(+), 11 deletions(-)

On 27/08/24 00:04, 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. Keep count of current
> tuning iteration using tuning_loop. 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>

Still doesn't compile:

  CC [M]  drivers/mmc/host/sdhci_am654.o
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);
      |                        ^~~
cc1: all warnings being treated as errors

Fix that and you can add:

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

> ---
> Changes since v2:
> - Use do while loop instead of while in patch 1/2
> - Move initialization of tuning_loop to sdhci_am654_init
> - Separate error path in patch 1/2
> ---
>  drivers/mmc/host/sdhci_am654.c | 46 ++++++++++++++++++++++++++--------
>  1 file changed, 35 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci_am654.c b/drivers/mmc/host/sdhci_am654.c
> index 64e10f7c9faa3..13da003363e1d 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;
>  
>  #define SDHCI_AM654_QUIRK_FORCE_CDTEST BIT(0)
>  };
> @@ -443,7 +445,7 @@ static u32 sdhci_am654_cqhci_irq(struct sdhci_host *host, u32 intmask)
>  #define ITAPDLY_LENGTH 32
>  #define ITAPDLY_LAST_INDEX (ITAPDLY_LENGTH - 1)
>  
> -static u32 sdhci_am654_calculate_itap(struct sdhci_host *host, struct window
> +static int sdhci_am654_calculate_itap(struct sdhci_host *host, struct window
>  			  *fail_window, u8 num_fails, bool circular_buffer)
>  {
>  	u8 itap = 0, start_fail = 0, end_fail = 0, pass_length = 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;
> @@ -494,8 +498,8 @@ 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);
> @@ -532,13 +536,30 @@ 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);
> +	return 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]);
> +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;
> +	int itapdly;
>  
> +	do {
> +		itapdly = sdhci_am654_do_tuning(host, opcode);
> +		if (itapdly >= 0)
> +			break;
> +	} while (++sdhci_am654->tuning_loop < RETRY_TUNING_MAX);
> +
> +	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] = itap;
> +	sdhci_am654->itap_del_sel[timing] = itapdly;
>  
>  	return 0;
>  }
> @@ -742,6 +763,9 @@ static int sdhci_am654_init(struct sdhci_host *host)
>  	regmap_update_bits(sdhci_am654->base, CTL_CFG_3, TUNINGFORSDR50_MASK,
>  			   TUNINGFORSDR50_MASK);
>  
> +	/* Use to re-execute tuning */
> +	sdhci_am654->tuning_loop = 0;
> +
>  	ret = sdhci_setup_host(host);
>  	if (ret)
>  		return ret;