Re: [PATCH 2/2] mmc: sdhci_am654: Add tuning debug prints

Judith Mendez
2024-08-20T20:19:02Z

On 8/20/24 10:03 AM, Ulf Hansson wrote:
> On Tue, 20 Aug 2024 at 16:41, Judith Mendez <jm@ti.com> wrote:
>>
>> Hi Ulf Hansson,
>>
>> On 8/20/24 6:33 AM, Ulf Hansson wrote:
>>> On Thu, 15 Aug 2024 at 22:15, Judith Mendez <jm@ti.com> wrote:
>>>>
>>>> Add debug prints to tuning algorithm for debugging.
>>>>
>>>> Signed-off-by: Judith Mendez <jm@ti.com>
>>>> ---
>>>> drivers/mmc/host/sdhci_am654.c | 5 +++++
>>>> 1 file changed, 5 insertions(+)
>>>>
>>>> diff --git a/drivers/mmc/host/sdhci_am654.c b/drivers/mmc/host/sdhci_am654.c
>>>> index c3d485bd4d553..a909f8de0eabe 100644
>>>> --- a/drivers/mmc/host/sdhci_am654.c
>>>> +++ b/drivers/mmc/host/sdhci_am654.c
>>>> @@ -457,11 +457,13 @@ static u32 sdhci_am654_calculate_itap(struct sdhci_host *host, struct window
>>>>
>>>> if (!num_fails) {
>>>> /* Retry tuning */
>>>> + dev_err(dev, "No failing region found, retry tuning\n");
>>>
>>> A dev_err seems to be too heavy, but I am not sure at what frequency
>>> this could occur?
>>
>> Having no failing region is what we call a corner case, it rarely
>> happens. The one case where it did happen, it took a good amount
>> of time to discover there were no failing regions found. The tuning
>> algorithm had to be looped 3 times before finding a failing itapdly.
>>
>>>
>>> Why isn't a dev_dbg sufficient?
>>
>> I thought about using dev_dbg, but based on some feedback after coming
>> upon this issue on a board bring up case, we think it would help
>> enormously if we make it as obvious as possible when no failing region
>> is found.
>>
>> The one case where this came up, the dev_err print would only print 3
>> times... Now this is only one case and we are not aware of any more
>> cases like this, also we cannot replicate on TI EVM's.
>
> What happens if/when we fail here? Do we fail to detect the card or do
> we end up running it in some degraded mode?
>
> If the latter a dev_warn, the former a dev_err(). Does that make sense?
>
>>
>>>
>>>> return -1;
>>>> }
>>>>
>>>> if (fail_window->length == ITAPDLY_LENGTH) {
>>>> /* Retry tuning */
>>>> + dev_err(dev, "No passing ITAPDLY, retry tuning\n");
>>>
>>> Ditto.
>>
>> Same idea as above..
>>
>> But with this print, the maximum amount of prints that could be printed
>> is 20, is this too many prints in your opinion?
>
> This sounds like dev_dbg to me. We are not really failing, as we are
> making a re-try and will most likely succeed then, right?

Yes absolutely right, will fix for v2, thanks.

~ Judith

>
>>
>>
>>>
>>>> return -1;
>>>> }
>>>>
>>>> @@ -505,6 +507,7 @@ static int sdhci_am654_platform_execute_tuning(struct sdhci_host *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;
>>>> @@ -542,12 +545,14 @@ static int sdhci_am654_platform_execute_tuning(struct sdhci_host *host,
>>>>
>>>> if (ret >= 0) {
>>>> itap = ret;
>>>> + dev_dbg(dev, "Final ITAPDLY=%d\n", itap);
>>>> 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);
>>>> } else {
>>>> + dev_err(dev, "Failed to find ITAPDLY, fail tuning\n");
>>>
>>> The commit message only talks about debug messages, but this is an
>>> error message. Perhaps update the commit message a bit?
>>
>> Sure will do, after we conclude the discussion above and in v2.
>>
>> Thanks so much for reviewing.
>>
>
> Kind regards
> Uffe