On 17 June 2011 17:39, Daniel Drake <dsd@xxxxxxxxxx> wrote: > If we power down the card, and then *immediately* power it on again > (and performing the CMD5,5,3,7 init sequence), the card fails to > respond to the first CMD5. > > We have identified two workarounds to this problem: > 1. If we wait 300ms after powering off the card before turning it on > again, it works fine. > > 2. If we perform a SDIO I/O reset after powering on, before starting > the 5,5,3,7 sequence, it works fine. I would still be interested in any comments you have on this issue, but actually it appears that it is probably related to the way that the SD8686 power line is wired up on our motherboard. OLPC's hardware team apologetically says "There are no turn-off clamps on the WLAN power. What that means is that when you turn off the power there isn't anything that will quickly pull the voltage down to zero or near zero. So when you turn off the power it takes time for the voltage to decay. With the amount of capacitance on that rail 300ms decay time doesn't sound unreasonable. You will have to delay or use the SDIO reset method." Thanks, Daniel -- 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
