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

Adrian Hunter
2024-08-21T05:37:12Z

On 15/08/24 23:15, 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's have been observed to never
> find a failing itapdly on the first couple of tuning
> iterations, but eventually do. It 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>
> ---
> drivers/mmc/host/sdhci_am654.c | 30 +++++++++++++++++++++++-------
> 1 file changed, 23 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/mmc/host/sdhci_am654.c b/drivers/mmc/host/sdhci_am654.c
> index 64e10f7c9faa3..c3d485bd4d553 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)
> };
> @@ -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;
> @@ -504,6 +508,7 @@ static int sdhci_am654_platform_execute_tuning(struct sdhci_host *host,
> u8 curr_pass, itap;
> u8 fail_index = 0;
> u8 prev_pass = 1;
> + int ret;
>
> memset(fail_window, 0, sizeof(fail_window));
>
> @@ -532,10 +537,20 @@ 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]);
> + if (ret >= 0) {
> + itap = ret;
> + sdhci_am654_write_itapdly(sdhci_am654, itap, sdhci_am654->itap_del_ena[timing]);
> + } else {
> + if (sdhci_am654->tuning_loop < RETRY_TUNING_MAX) {
> + sdhci_am654->tuning_loop++;
> + sdhci_am654_platform_execute_tuning(host, opcode);

The kernel uses very small stack size, so recursive function calls
should not be used. It would be better to put the loop in a separate
function, or add a retry: label and goto retry.

> + } else {
> + return -1;
> + }
> + }
>
> /* Save ITAPDLY */
> sdhci_am654->itap_del_sel[timing] = itap;
> @@ -908,6 +923,7 @@ static int sdhci_am654_probe(struct platform_device *pdev)
> goto err_pltfm_free;
> }
>
> + sdhci_am654->tuning_loop = 0;

So this is 10 retries ever, since sdhci_am654->tuning_loop is never
set back to 0. Is that the intention?

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