2011/1/7 Hein_Tibosch <hein_tibo...@yahoo.es>: > Maybe a stupid question, but when designing new hardware with a slot > for an sd-card, how essential is it that the driver is able to power off/on > the card?
For one, this is needed for power-management. In powered suspend case, when card's slot does not provide card change detection, power-cycle is the only way sure way to get a card to known state in case it can be removed in that time. > I would say essential, because I've seen sd-cards in a state in which they > didn't respond to MMC_GO_IDLE_STATE anymore, until they were re-inserted. > > Can anyone shed a light on this? How could an sd-card get into such a state? After CMD15 (GO_INACTIVE_STATE) or because of a card bug. > > Will the mmc driver fall back to mmc_rescan() after an initialized card > becomes non-responsive? When the card goes off-protocol it's in undefined state, so a reset is the only way to get it back to known state. Since in SD/MMC there's no reset signal - only power cycle can reset the card. Best Regards, Michał Mirosław -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
