[RFC PATCH] mmc: zynq_sdhci: Dependable card detect

[Stefan Herbrechtsmeier]

Hi Ashok,

Am 18.05.2023 um 08:20 schrieb Soma, Ashok Reddy:

>   We haven't seen any instability issue so far on ZynqMP boards and no one reported any such issue till now.

It isn't an instability issue. The high level at the card detect input 
is not marked as stable until a short low level is detected.

>   We are already taking care of card detection stability issue with below waiting logic.
> https://source.denx.de/u-boot/u-boot/-/blob/master/drivers/mmc/zynq_sdhci.c#L1161

This code makes problems for us. The SDHCI_CARD_STATE_STABLE signal 
isn't set without a card and we see a "Sdhci card detect state not 
stable" message.

> Could you please answer below questions.
>   1. is this observed in SPL only or full u-boot ?

Both. We have enable environment support in SPL and see the "Sdhci card 
detect state not stable" message after "Loading Environment from MMC..." 
in SPL and "MMC: " in full U-Boot.

>   2. is this observed in dynamic config case only ? because your patch is in dynamic path.

No. I have override the return value of the 
zynqmp_pm_is_function_supported function and see the same error. Without 
dynamic case I don't see a possibility to set the SD_CONFIG_EMMC_SEL value.

>   3. "On our hardware we get a "Sdhci card detect state not stable" error in the SPL if no mmc card is present"
>         Are you seeing stability issue when card is not present ?

No, the SDHCI_CARD_STATE_STABLE  signal is never set.

>   can you please elaborate more about the issue.

I have change the code to monitor the SDHCI_PRESENT_STATE signal. 
Without a card at boot the SDHCI_CARD_STATE_STABLE signal is unset. 
After card insert the SDHCI_CARD_PRESENT signal and the 
SDHCI_CARD_STATE_STABLE signal is set after some time. After card remove 
the SDHCI_CARD_STATE_STABLE signal is set and the SDHCI_CARD_PRESENT 
signal is unset after some time. It doesn't matter if a physical card is 
insert or the SD_CONFIG_EMMC_SEL config  is used to emulate a present 
card. Without a short card present signal on the card detect logic the 
SDHCI_CARD_STATE_STABLE signal isn't set.

>   4.  It is not convincing to me that you are trying to select eMMC for some time and then switching back to SD.

I don't find a documentation what the consequence of this config is but 
this config is set based on the value of "non-removable" and setting 
this config with enabled clock leads to a functional 
SDHCI_CARD_STATE_STABLE signal even after unset of the config.

Maybe the SD_CDn_CTRL register have the same result but this isn't 
available via PMU.

Regards
   Stefan

>> -----Original Message-----
>> From: U-Boot <u-boot-bounces at lists.denx.de> On Behalf Of Stefan
>> Herbrechtsmeier
>> Sent: Tuesday, May 16, 2023 7:51 PM
>> To: u-boot at lists.denx.de
>> Cc: Stefan Herbrechtsmeier <stefan.herbrechtsmeier at weidmueller.com>;
>> Jaehoon Chung <jh80.chung at samsung.com>; Simek, Michal
>> <michal.simek at amd.com>; Peng Fan <peng.fan at nxp.com>
>> Subject: [RFC PATCH] mmc: zynq_sdhci: Dependable card detect
>>
>> CAUTION: This message has originated from an External Source. Please use
>> proper judgment and caution when opening attachments, clicking links, or
>> responding to this email.
>>
>>
>> From: Stefan Herbrechtsmeier <stefan.herbrechtsmeier at weidmueller.com>
>>
>> The card detect logic needs a short card present signal to work dependable.
>> Without a present card the SDHCI_CARD_STATE_STABLE signal is not set
>> dependable after a reset. Use the internal fixed card present signal to initiate
>> the card detect logic.
>>
>> Signed-off-by: Stefan Herbrechtsmeier
>> <stefan.herbrechtsmeier at weidmueller.com>
>>
>> ---
>> On our hardware we get a "Sdhci card detect state not stable" error in the SPL
>> if no mmc card is present. It is unclear if this patch is the correct solution, but
>> a short card inserts or a fixed card present signal leads to a
>> SDHCI_CARD_STATE_STABLE signal with and without card.
>>
>>   drivers/mmc/zynq_sdhci.c | 20 ++++++++++++++++++++
>>   1 file changed, 20 insertions(+)
>>
>> diff --git a/drivers/mmc/zynq_sdhci.c b/drivers/mmc/zynq_sdhci.c index
>> e44868aaec..a88feeb367 100644
>> --- a/drivers/mmc/zynq_sdhci.c
>> +++ b/drivers/mmc/zynq_sdhci.c
>> @@ -1075,6 +1075,26 @@ static int
>> sdhci_zynqmp_set_dynamic_config(struct arasan_sdhci_priv *priv,
>>                  return ret;
>>          }
>>
>> +       /* The card detect logic needs a short card present signal to work
>> +        * dependable. Without a present card the SDHCI_CARD_STATE_STABLE
>> +        * signal is not set dependable after a reset. Use the internal
>> +        * fixed card present signal to initiate the card detect logic.
>> +        */
>> +       if (!dev_read_bool(dev, "non-removable")) {
>> +               ret = zynqmp_pm_set_sd_config(priv->node_id,
>> SD_CONFIG_EMMC_SEL,
>> +                                             1);
>> +               if (ret) {
>> +                       dev_err(dev, "SD_CONFIG_EMMC_SEL failed\n");
>> +                       return ret;
>> +               }
>> +               ret = zynqmp_pm_set_sd_config(priv->node_id,
>> SD_CONFIG_EMMC_SEL,
>> +                                             0);
>> +               if (ret) {
>> +                       dev_err(dev, "SD_CONFIG_EMMC_SEL failed\n");
>> +                       return ret;
>> +               }
>> +       }
>> +
>>          return 0;
>>   }
>>   #endif
>> --
>> 2.30.2