From: Marek Vasut [mailto:marex@xxxxxxx] Sent: Wednesday, April 5, 2023 8:47 PM > On 4/5/23 20:24, Christoph Niedermaier wrote: >> From: Marek Vasut [mailto:marex@xxxxxxx] >> Sent: Wednesday, April 5, 2023 6:25 PM >>> On 4/5/23 18:02, Christoph Niedermaier wrote: >>> >>> [...] >>> >>>> +/ { >>>> + model = "DH electronics i.MX6ULL DHCOR on maveo box"; >>>> + compatible = "dh,imx6ull-dhcor-maveo-box", "dh,imx6ull-dhcor-som", >>>> + "fsl,imx6ull"; >>>> + >>>> + aliases { >>>> + /delete-property/ mmc0; /* Avoid double definitions */ >>>> + /delete-property/ mmc1; >>>> + mmc2 = &usdhc2; /* eMMC should be mmc2 */ >>> >>> Why not mmc0 ? >>> >>> Use root=PARTUUID= when booting to avoid any dependency on >>> root=/dev/mmcblk2pN enumeration. >> >> This is due to software interchangeability with the DHCOM >> i.MX6ULL, where the eMMC is always mmc2. > > +CC Ulf , I vaguely recall some discussion about this enumeration and I > am not sure one can really depend on that. That why I think it good to have a defined number for mmcblk devices on an embedded system. An excerpt from [1]: Alternative solutions like PARTUUIDs do not cover the case where multiple mmcblk devices contain the same image. This is a common issue on devices that can boot both from eMMC (for regular boot) and SD cards (as a temporary boot medium for development). When a firmware image is installed to eMMC after a test boot via SD card, there will be no reliable way to refer to a specific device using (PART)UUIDs oder LABELs [1] https://patchwork.kernel.org/project/linux-mmc/patch/20200825134441.17537-2-matthias.schiffer@xxxxxxxxxxxxxxx/ So far I have never had a problem with numbering mmcblk devices via aliases. Regards Christoph
