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

Judith Mendez
2024-08-21T14:14:38Z

Hi Adrian,

On 8/21/24 12:37 AM, Adrian Hunter wrote:
> 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.

Ok, can change to this method, I was not sure of recursive function
call but had opted for that since the code was to be simpler.

>
>> + } 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?

Yes, maximum of 10 re-tries. So far we have only seen issues during
boot.

~ Judith

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