On Mon, Oct 24, 2011 at 10:05:30AM +0200, Ulf Hansson wrote: > Sebastian Rasmussen wrote: >> Hi! >> >>> Err, no. You're not allowed to power down the card between commands >>> unless the card has been removed or been has finished with. >>> >>> If you power down the card (which you _are_ doing by writing zero to >>> the MMCIPOWER register), then you have to do a full setup of the card >>> when you resume. >> >> MCIPower is according to ARM PL180 TRM signalling to an external power >> supply to turn on/off (MCIPWR), whether to use open-drain (MCIROD), >> what voltage to use (MCIVDD) and whether the card is clocked (MCICLK). >> >> According ST-Ericsson's public PL180 derivative spec[1] it seems to work >> roughly in same way (but renaming the register SDI_PWR and the signals >> SDIPWR & SDICLK). However, there is no SDIVDD as the derivative can not >> signal desired voltage level externally (there are no bits in SDI_PWR for this). >> This makes it plausible that SDIPWR may not be routed externally either. >> Can you verify this as there are no signal routing diagrams in the spec..? >> > > The hole idea with this PM patch is to make sure the vcore regulator and > the clock are disabled in runtime_suspend to be able to save a huge > amount of current in "idle" mode. > > Disabling the vcore regulator will sooner or later (depending on your > regulator tree) mean that that power to the controller is actually cut, > which then means that all registers will be "cleared" including the > MCIPWR. So the actual reason for clearing the registers in the > runtime_suspend function is because of two reasons. > > 1. Set the controller in a known state so no "magic" things happens when > we are runtime suspended, for example getting an IRQ. > > 2. Save power by disabling the clock etc. The actual power to the > controller does not have to be cut just because we have disabled the > vore regulator. > > If the ARM PL180 TRM prevent us from from doing this kind of operations > in runtime_suspend, we must think of an alternative solution which just > apply for ST-Ericssons derivative of PL180. THIS IS VERY IMPORTANT to be > able to implement a proper power management solution. > > Please check this Russell, this is VERY IMPORTANT! I repeat: if you cut power to the card, you have to re-initialize it. Re-initialization takes quite a bit of time to re-detect and setup the card. You'd also need to re-configure things like the transfer mode and so forth. The other problem is if you're doing runtime-pm between commands, the re-initialization takes multiple commands - we don't want to be in the middle of a reinitialization while we're also doing something with runtime-pm - nested initialization would not be a nice problem to solve. -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
