On 6 April 2018 at 02:50, Jennifer Dahm <jennifer.dahm@xxxxxx> wrote: > i Ulf, > > On Wed, 4 Apr 2018, Ulf Hansson wrote: >> On 29 March 2018 at 19:44, Jennifer Dahm <jennifer.dahm@xxxxxx> wrote: >> > From: Kyle Roeschley <kyle.roeschley@xxxxxx> >> > >> > On some SD host controllers, 1.8V signaling is required for reliable >> > operation of the part. Add a capability which says that we must switch >> > to 1.8V signaling during card initialization. >> >> This makes no sense to me, sorry. SD cards, according to the spec, >> must always be initialized at 3.3 V I/O, before they can be switched >> to UHS mode and 1.8 V I/O. >> >> So if your host have issues with supporting 3.3 V I/O for an SD card >> slot, you are in trouble anyways. Or what am I missing? >> >> Kind regards >> Uffe > > The key here is in the second patch description. Our controller has no > problem using 3.3V for short periods of time - to negotiate down to > 1.8V, for example. The problem is when 3.3V is used continuously for > long periods of time. The fix for us is to require that cards used > with this controller support 1.8V signaling. > > For convenience, here's the description from the second patch: > >> mmc: sdhci-pci: Require 1.8V signaling on some NI 904x >> >> On some NI 904x devices, using 3.3V signaling for extended periods of >> time will physically damage the pads connected to the SDHC, eventually >> causing complete failure of the controller. To work around this, require >> that we use 1.8V signaling. Ahh, that makes more sense. Seems like you should extend the changelog for the first patch to make it more clear. Anyway, let me move back to reviewing the code. Separate thread. >> >> Signed-off-by: Kyle Roeschley <kyle.roeschley@xxxxxx> >> Signed-off-by: Jennifer Dahm <jennifer.dahm@xxxxxx> > > I hope this makes better sense! > > Best, > Jennifer Dahm Kind regards Uffe -- 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
