Am 24.12.19 um 13:38 schrieb Matthias Brugger: > > On 24/12/2019 12:56, Stefan Wahren wrote: >> Hi Matthias, >> >> Am 23.12.19 um 21:20 schrieb Matthias Brugger: >>> Hi Stefan, >>> >>> On 23/12/2019 19:51, Stefan Wahren wrote: >>>> Am 20.12.19 um 14:58 schrieb Stefan Wahren: >>>>> Hi, >>>>> >>>>> i tried to run current U-Boot (rpi_4_32b_defconfig) on my RPi 4 with >>>>> bcm2711-rpi-4-b.dtb from the upstream kernel. Unfortunately i only see >>>>> garbage on the debug UART (pin 14 & 15). Using the DTB from the >>>>> downstream kernel has a proper UART output. The config.txt contains >>>>> debug_uart=1 >>>>> >>>>> I compared both and identified an offending Linux commit: >>>>> ARM: dts: bcm283x: Remove brcm,bcm2835-pl011 compatible >>>>> >>>>> Unfortunately reverting this patch still doesn't fix the issue. Any ideas? >>>> After hours of playing with the DTB, i finally found the reason why the >>>> upstream kernel DTB doesn't work with U-Boot on RPI 4. The DTS must be >>>> compiled with flag "-@". >>>> >>>> It isn't clear to me, why this is necessary but it would be nice to make >>>> U-Boot work without this. >>>> >>> Can you provide the exact command you are using? >> i didn't call dtc directly via command line. I just added this Makefile >> hack [1] to the Linux upstream tree. This will add a __symbols__ section >> to the DTB which is required for overlays. You can verify this with dtdiff. >> >> Since the upstream kernel boots without the __symbols__ section, i think >> this garbage output issue could be fixed in u-boot. >> > Little by little I grasp what you are doing. So you compile the DTB in the > kernel, then pass the blob to u-boot and add it with OF_EMBED? Is that > correct?
I use a recent Raspbian image, replace the bcm2711 DTB with the upstream kernel ones (yes build with make dtbs) and kernel7.img with u-boot.bin (renamed all the other kernel binaries to make sure kernel7.img is really used). Also use a boot.scr from here, but not sure this have an influence [1]. I used the rpi_4_32b_defconfig without any modifications like OF_EMBED. I assume u-boot uses the FDT image passed by the Raspberry Pi bootloader. [1] - https://andrei.gherzan.ro/linux/uboot-on-rpi/ > > Regards, > Matthias
