Hi Romain, On Mon, 19 Aug 2024 at 01:15, Romain Crausaz <crausaz.rom...@gmail.com> wrote: > > Hi Simon, Hi Peter, > > First of all, thanks a lot for your answers. > > 1. When I enable the i2c bus in the config.txt (which is parsed by the rpi > first stage bootloader), the overlay put this as compatible:"brcm,bcm2835". I > checked in the source of U-Boot and the driver is not available. > 2. One solution could be to use the i2c-gpio driver instead of the default > i2c controller. U-Boot has this driver. > 3. Since the device tree passed by the rpi bootloader is stored in the > variable fw_dtb_pointer (see the lowlevel_init.S) would I be able to do the > following: > 3.1 remove the automatic selection for the device tree passed by the rpi > bootload > 3.2 system starts and use the default device tree where the i2c bus is > defined with i2c-gpio, access the device I need and store the information > needed > 3.3 get the device tree address from fw_dtb_pointer, set fdt address fdt > addr with the new device tree and then start the kernel > > I have another question, what triggers the DM to check for the device (with > dm tree command there is a X under the column probed). Because here we could > have a really simple device tree with the minimum configuration for just the > i2c and load it from U-Boot, perform the action needed and then boot the > kernel by passing the device tree provided by the first stage bootloder.
Just a little niggle, please avoid top-posting as it messes up the history for later readers. U-Boot devices are probed when used. So you could use the 'i2c' command to make it be probed. Regards, Simon > > Regards > Romain > > > > Le sam. 17 août 2024 à 17:57, Simon Glass <s...@chromium.org> a écrit : >> >> +Peter Robinson >> +Matthias Brugger >> >> Hi Romain, >> >> On Sat, 17 Aug 2024 at 07:01, Romain Crausaz <crausaz.rom...@gmail.com> >> wrote: >> > >> > Hi all, >> > >> > >> > >> > I am currently facing an issue with U-Boot and a raspberry pi CM4. Here is >> > the setup: >> > >> > >> > >> > 1. Yocto Scarthgap >> > >> > 2. U-Boot 2024.01 >> > >> > 3. rpi_arm64_defconfig >> > >> > >> > >> > I am trying to access the i2c bus from U-Boot. I have been trying to modify >> > the device tree which is referenced as >> > “CONFIG_DEFAULT_DEVICE_TREE="bcm2711-rpi-4-b”” in the defconfig without >> > success. I can remove everything, set all nodes to disabled and I see no >> > change in U-Boot (I am using dm commands to check the status of the >> > peripherals). >> > >> > >> > >> > It seems that with the rpi, U-Boot will only configure itself against the >> > device tree passed by the bootloader of RPI. Could someone confirm this ? >> >> Yes. It isn't quite obvious, but this is a clue: >> >> Core: 211 devices, 16 uclasses, devicetree: board >> >> 'board' means that the board can do whatever it wants. >> >> > >> > >> > >> > Is there a way to configure / modify U-Boot to use its own devicetree and >> > simply pass the device tree generated by the rpi bootloader to the kernel ? >> > >> > >> > >> > Because the second issue is that the i2c driver defined in the device tree >> > passed to u-boot is not available in u-boot. >> > >> > >> > >> > Thanks for your help >> >> Since OF_HAS_PRIOR_STAGE is a hidden option, you cannot disable it in >> the defconfig. The only way I know of is to comment out the 'imply >> OF_HAS_PRIOR_STAGE' in ARCH_BCM283X in arch/arm/Kconfig >> >> For me, that stops the rpi_4 booting, so perhaps the devicetree is >> out-of-date or ft_board_setup() is doing something strange, or >> something else. The in-tree devicetree may have got out-of-date, so >> perhaps use the Linux one. >> >> Regards, >> Simon
