Hi again,
On 5/11/2026 10:30 AM, Jonas Karlman wrote:
> Hi,
>
> On 5/11/2026 9:49 AM, Ye Li wrote:
>> SD initialization failure happens with some UHS-I SD cards on
>> iMX8MM/iMX93/iMX91 EVK after
>> commit 4fcba5d556b4 ("regulator: implement basic reference counter").
>> When sending operation condition to SD card, the OCR does not return
>> correct status. The root cause is regulator on/off delay is missed
>> in MMC power cycle with above commit, so SD card is not completely
>> power off.
>>
>> When SD startup, the sequence of MMC power cycle is:
>> mmc_power_init(get vmmc_supply dev) -> mmc_power_off -> udelay(2000)
>> -> mmc_power_on
>>
>> Before above commit, as a fixed regulator, the GPIO is set as:
>> GPIO inactive (in mmc_power_init) ->
>> GPIO inactive and delay off-on-delay-us (in mmc_power_off) ->
>> udelay(2000) ->
>> GPIO active (in mmc_power_on)
>>
>> After the commit:
>> GPIO inactive (in mmc_power_init) ->
>> enable_count is 0, regulator_set_enable returns -EALREADY immediately,
>> so GPIO is inactive but No off-on-delay-us (in mmc_power_off) ->
If the regulator is off at boot-on then this is working as intended.
However, if probing the regulator turns it off and that requires a
off-on-delay-us delay, maybe you are missing a regulator-boot-on
property to indicate that the regulator is on at boot/reset. That should
also align the enable count with boot-on state of the regulator.
Looking at the kernel the off-on-delay-us is applied before a regulator
is enabled, not after it is disabled like in U-Boot. Maybe U-Boot should
do something similar, in simplest form always udelay off-on-delay-us
before the regulator is enabled.
>> udelay(2000) ->
>> GPIO active (in mmc_power_on)
>>
>> Add the on/off delay and startup delay after GPIO request in
>> regulator_common_of_to_plat which is called in regulator device probing.
>> So in mmc_power_init, after GPIO is set to default inactive, the
>> off-on-delay-us is applied.
>>
>> Signed-off-by: Ye Li <[email protected]>
>> ---
>> drivers/power/regulator/regulator_common.c | 6 ++++++
>> 1 file changed, 6 insertions(+)
>>
>> diff --git a/drivers/power/regulator/regulator_common.c
>> b/drivers/power/regulator/regulator_common.c
>> index 85af8d599ad..158284a3309 100644
>> --- a/drivers/power/regulator/regulator_common.c
>> +++ b/drivers/power/regulator/regulator_common.c
>> @@ -46,6 +46,12 @@ int regulator_common_of_to_plat(struct udevice *dev,
>> dev_read_u32_default(dev, "u-boot,off-on-delay-us", 0);
>> }
>>
>> + if ((flags & GPIOD_IS_OUT_ACTIVE) && plat->startup_delay_us)
>> + udelay(plat->startup_delay_us);
>> +
>> + if (!(flags & GPIOD_IS_OUT_ACTIVE) && plat->off_on_delay_us)
>> + udelay(plat->off_on_delay_us);
>
> regulator_common_of_to_plat() is for parsing the values, no udelay()
> should be applied here.
>
> regulator_common_set_enable() applies udelay() when the regulator is
> enabled.
Or disabled.
>
> Does your regulator .get_enable() ops not being called or does it not
> implement its own udelay() based on parsed values?
I meant set_enable() here :-)
Regards,
Jonas
>
> Regards,
> Jonas
>
>> +
>> return 0;
>> }
>>
>
