On 18 August 2016 at 14:25, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote: > On 11/08/16 03:48, Shawn Lin wrote: >> + Adrian >> >> Let's queue Adrian here who now maintains SDHCI stuff. > > SDHCI drivers may not implement no-1-8-v in a consistent manner, but as far > as I can see, the meaning is still clear: 1.8V will not be used for either > supply or signaling. Okay. > > SDHCI is complicated because the SDHCI specification does not cover eMMC. > From the perspective of SDHCI, the only 1.8V modes are the UHS-I modes, so > support for 1.8V signaling is the same as support for one of those modes > (the spec even says as much). But what happens is that the host controller > can support those modes but the board can't supply 1.8V so the drivers > remove capability for the modes. Support for 1.8V supply has a capability > bit which drivers can override if necessary but removable SD cards don't > support 1.8V supply anyway, so the issue doesn't arise if the host > controller is only used for uSD cards. By looking how SDHCI uses the SDHCI_SUPPORT_DDR50 in conjunction with SDHCI_QUIRK2_NO_1_8_V (which is set when no-1-8-v DT property is provided), this becomes a bit messy. >From Adrian's summary above, it then seems appropriate to limit the no-1-8-v DT property to apply only to capabilities related to SD cards, as I assume that also was the original purpose. Do you think it's possible to clean up this in sdhci when assigning the caps masks, and then also clarify the no-1-8-v DT binding in the documentation? Regarding the new DT binding proposed to be added, mmc-ddr-3_3v, it seems we need this to be able to properly describe the HW. Rob, do you have an issue with adding this binding? I am thinking that we already have mmc-ddr-1_8v and mmc-ddr-1_2v, so it just follow existing pattern. [...] 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
