On Mon, 2023-11-13 at 17:07 -0600, Jon Humphreys wrote: > > > Firmware locations: > > > ------------------- > > > - the EBBR states that a dedicated partition is preferred for storing > > > firmware. This seems to imply that all firmwares will be in a single > > > location. This isn't true in many cases (eg, some partitions aren't > > > large enough and subsequent stages are loaded from a different > > > partition). Is there guidance (or should be guidance) in EBBR on how > > > to handle these scenarios? > > > > Not sure what you mean here. In general if a partition containing a > > filesystem isn't big enough then we can just make it bigger... > > Not always. Consider a eMMC hardware partition that is limited in size. > For example, BeaglePlay will put the first stage SPL in the eMMC hardware > partition > and other stages (eg, u-boot) in the UDA partition, so that all stages > will fit.
The smallest eMMC HW boot partition I've ever seen was ~4MiB many years ago. More modern eMMC have 8, 16 or even 32MiB. I'd expect that to be enough for all firmware components (perhaps even including OP-TEE). > From what you have said, the main point is to reduce the possibility of > the OS messing with the firmware, so the spec recommends that the > firmware be in dedicated partitions. This is clear at the beginning of > chapter 4: > > In general, EBBR compliant platforms should use dedicated > storage for boot firmware images and data ... > > What confused me is that 4.2 goes a bit further is specifying firmware > to be stored in "a dedicated firmware partition". (But no SHALLs here!) > Maybe replace "a dedicated firmware partition" with "dedicated firmware > partitions". One thing to keep in mind is that using only the HW boot partition for all firmware components simplifies atomic updates a lot. Otherwise you'd need to have either use matching A/B partitions in the UDA for the later components or ensure compatibility across SPL/main u-boot versions. Jan -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ boot-architecture mailing list -- boot-architecture@lists.linaro.org To unsubscribe send an email to boot-architecture-le...@lists.linaro.org
