On Mon, Nov 10, 2025 at 08:46:39PM +0000, Christoph Stoidner wrote: >Hi Peng, thanks for your feedback. > >> Hi Christoph >> >> Thanks for your patch. >> >> > Subject: [PATCH] mmc: Fix missing 1 ms delay after mmc power up >... >> > + udelay(2000); >> >> Per spec, >> From Figure 6-4: Power-up Diagram of Card >> the 1ms is voltageSupply ramp up time, so I am thinking the fix >> should be in your regulator side, saying startup-delay-us property >> in your regulator node. > >True, this could also be handled via the regulator?s DTS properties, and >some boards already do that. However, from my point of view, that?s not >the right place for this particular delay. > >The SD specification distinguishes between two different delays >(see Figure 6-5 ?Power-Up Diagram (Host)? in SD Spec 6.00, ?6.4.1): > > 1) "Power ramp up" > 2) "Stable voltage delay" > >The first one (power ramp up) is regulator-specific and should indeed be >covered by the regulator?s startup-delay-us property in the device tree. >But this patch is about the second one - the "stable voltage delay". > >That delay is completely independent of any regulator/voltage-supply or >board characteristics; it is a constant 1ms delay by the SD interface itself >to ensure correct card initialization timing. >Decoupling it from the regulators would make board-code developers >live easier, and can make U-Boot?s MMC initialization more robust across >all boards. > >What do you think about that?
Sorry for late. Thanks for explaining this, this is reasonable. I am thinking it might be better if we add ios.post_power_delay_ms for your platform. Regards Peng > >Regards, >Christoph > >> Thanks, >> Peng. >> >> > + return ret; >...
