Hi Peng, On Di, 2025-11-18 at 12:56 +0800, Peng Fan wrote: > 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.
you mean we should introduce the DTS property post_power_delay_ms for mmc and then use it in our platform's DTS? But a DTS property is actually what I want to avoid, because that delay is nothing platform-specific and should be solved all for one in the mmc subsystem drivers/mmc/mmc.c itself. What's the reason why you prefer a DTS property? Regards, Christoph > > Regards > Peng > > > > > Regards, > > Christoph > > > > > Thanks, > > > Peng. > > > > > > > + return ret; > > ...
