On Sat, Jun 18, 2011 at 5:37 PM, Daniel Drake <dsd@xxxxxxxxxx> wrote: > 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 Hi, Daniel How do you power off 8686 now? Use RESETn, PDn, or directly control regulator? Assume RESETn is kept high as Ohad mentioned before, do you control PDn? If directly control regulator, the decay time is needed. It seems 8686 is not power off, so I/O reset is needed for init sequence (CMD5, 5, 3, 7). Thanks > -- > 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 > -- 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
