Re: [PATCH] mmc: core: Wait for Vdd to settle on card power off

[Adrian Hunter <adrian.hunter@intel.com>]

On 7/03/25 19:46, Erick Shepherd wrote:
>>> The SD spec version 6.0 section 6.4.1.5 requires that Vdd must be
>>> lowered to less than 0.5V for a minimum of 1 ms when powering off a
>>> card. Increase our wait to 15 ms so that voltage has time to drain down
>>> to 0.5V.
> 
>> mmc_power_off() has a delay.  So does mmc_power_cycle()
> 
>> Why does this need to be in sdhci?  Are you experiencing an
>> issue?
> 
> Thank you for taking a look at this. The initial change was made in
> mmc_power_off() due to an issue we had with some of our devices
> requiring more time for the Vdd to drain below 0.5V. Ulf gave us this
> feedback on that change:
> 
>> No, this isn't the proper place of adding more "magic" delays.
> 
>> Instead, make sure the related ->set_ios() callback in the mmc host
>> driver deals with this instead. In case it uses an external regulator,
>> via the regulator API, then this is something that should be
>> controlled with the definition of the regulator.
> 
> Should we take a different approach here? 

It probably should be dealt with in the ->set_power() callback.
Is it one of the PCI devices in sdhci-pci-core.c?