On Fri, Nov 13, 2015 at 06:54:14PM +0000, Trent Piepho wrote: > On Fri, 2015-11-13 at 11:28 +0100, Sascha Hauer wrote: > > > 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? > > Don't have the problem on Linux. The OF parsing works the same way, but > the dw driver stats with 0 bus-width caps, like how mxs and tegra-sdmmc > work. > > The linux dw_mmc driver allows "sub-drivers" to supply caps, and the > Exynos4/5 driver adds CAP_8_BIT. Which is probably broken, as it > doesn't add 4_BIT as well and will have the same problem with the device > tree not being able to remove bus widths. Ok, it seems the rationale behind the MMC_CAP_x_BIT_DATA is another one than thought it is. The host driver cannot know how a card is actually connected, so it should rely purely on the device tree bus-width property. So dw_mmc.c should start with host->mci.host_caps = 0 in the device tree case. If this is changed we'll also have to fix the platform_data for dw_mmc, it now needs a bus_width field to let ./arch/arm/mach-socfpga/xload.c work in 4 bit mode. 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
