Hi Trent, On Fri, Nov 13, 2015 at 12:36:22AM +0000, Trent Piepho wrote: > I found my 4-bit connected eMMC chip wasn't working because barebox was > trying to run it in 8-bit mode. I had the proper bus-width property in > the device tree, but this doesn't work. > > The problem is that mci_of_parse() uses bus-width to _add_ 8-bit and/or > 4-bit caps to the host. It doesn't remove any host_caps the driver > already has set. So if the driver supports 8-bit but the DT bus-width > is 4, you still get a driver that thinks 8-bit will work. > > You can see this in dw_mmc.c, dw_mmc_probe() sets: > host->mci.host_caps = MMC_CAP_4_BIT_DATA | MMC_CAP_8_BIT_DATA > then later > mci_of_parse(&host->mci); > return mci_register(&host->mci); > > The mci_of_parse call will not remove the 4 and 8 bits caps. There is > the same problem in imx-esdhc.c. The other two users of mci_of_parse, > mxs.c and tegra-sdmmc.c, don't have this problem, since they don't set > any bus-width host_caps in the driver and depend on the DT or > platform_data to have this info. > > With drivers split 50/50, which is the right way? Don't have the driver > report what bits it supports and depend on the device tree to have that > information? Or have of_mci_parse remove widths that aren't indicated > as supported in the DT, so that the DT can remove widths the hardware > indicates it supports. I think the resulting flags should be the subset of what all components can do, that is (driver_flags & devicetree_flags & card_flags). So mci_of_parse() should IMO clear the MMC_CAP_8_BIT_DATA flag if the bus-width property is set to 4. You should encounter the same problem under Linux, right? Sascha -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/barebox
