On Thu, Jul 23, 2015 at 10:17:29PM -0600, Stephen Warren wrote: > On 07/14/2015 09:44 AM, Simon Glass wrote: > > Hi Stephen, > > > > On 13 July 2015 at 22:52, Stephen Warren <swar...@wwwdotorg.org> wrote: > >> On 07/11/2015 08:04 AM, Simon Glass wrote: > >>> Hi Stephen, > >>> > >>> On 10 July 2015 at 23:34, Stephen Warren <swar...@wwwdotorg.org> wrote: > >>>> On 07/07/2015 08:53 PM, Simon Glass wrote: > >>>>> Raspberry Pi uses a DWC2 USB controller and a SMSC USB Ethernet adaptor. > >>>>> Neither of these currently support driver model. > >>>>> > >>>>> This series does the following: > >>>>> - Move Raspberry Pi to use device tree control (u-boot-dtb.bin instead > >>>>> of > >>>>> u-boot.bin) > >>>> > >>>> I'd strongly prefer not to do this. For one thing, it means we'd need > >>>> different U-Boot builds for each of the different RPi models, and we > >>>> currently don't need that (or perhaps we require users to create their > >>>> own u-boot-dtb.bin by choosing the right DTB to append). If it > >>> > >>> Why does device tree change how things work now? The get_board_rev() > >>> function currently deals with this. It doesn't look like rpi_board_rev > >>> is used anywhere else. > >> > >> Without a DT, the code is free to make all the board-rev-specific > >> decisions at run-time without external influence. > >> > >> With a DT, we either have to: > >> > >> a) Pick the DT for one particular board and use that everywhere, even if > >> it's incorrect for the actual board in use. > >> > >> b) Build a different U-Boot + DTB image for each board-rev, and put the > >> correct one on the SD card. > >> > >> Neither of those options seem like a good idea to me. > > > > How about: > > > > c) Leave the code as is, and not add a whole lot more device tree files. > > > > After all the kernel only has files for rpi and rpi_2. Why should we > > add one for each variant? If you don't want to do it, why do it? > > For the kernel I do expect to add a DT file for each variant. That makes > sense since we expect a single kernel binary to run unmodified on all > HW, parameterize the HW setup via the DTB, and have an infrastructure to > pass the different DTs to the kernel easily. > > For U-Boot, I'd like to continue to have a single-binary that runs on > all RPis (well, one for RPi 1, another for RPi 2). That's a very nice > usage model for users. That's not possible if U-Boot pulls everything > from DT and we have a different DT for each system (which only makes > sense so that we don't lie in the DT, or fail to represent the > differences between the models) since a single DT is embedded into the > U-Boot binary; there's no infra-structure to passing 1 of n DTBs to U-Boot.
So my question is, for what U-Boot needs, can we have 1 DT for RPi 1 (that's not lying about what the HW can do) and 1 DT for RPi 2? This is the kind of question I'm frankly strugling with right now on converting more of the TI boards to be DT based as well. -- Tom
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