Ulf, On Mon, Nov 24, 2014 at 5:29 AM, Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote: >> 2. Several people I've talked to have expressed concerns that our >> minimum value is 2.7V. Apparently that's really on the edge and makes >> EEs a little nervous. The quick sample of cards sitting on my desk >> shows that they seem to claim 0x00ff8000, which doesn't include 2.7V. > > 0x00ff8000 states what values of VDD levels the device supports. Not VIO. Yup, I was just pointing out that possibly others were trying to get a little bit of margin (not going all the way down to 2.7V) too. >> Both of the above make me feel like dw_mmc should try its best to pick >> a value for vqmmc that is closest to the value of vmmc (and >= 2.7V). >> That also happens to make us work exactly like hosts where vmmc and >> vqmmc are supplied by the same supply. > > I do see your point. And I agree that it would be nice to achieve > something like this. > > The question is how to do this. For sure, we need to involve the mmc > core to handle this correctly. You could add a function to the core that we could call from dw_mci_switch_voltage() and it would do all the work except trying to set the UHS register. That would certainly make it easy. That could try to set the highest voltage that is <= vmmc when we're at MMC_SIGNAL_VOLTAGE_330. -Doug -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
