Hi everyone, as the RaspberryPI kernel is nowadays "configured" by the device tree, there are some issues for the current openSUSE images.
By default the dtbs as shipped disable any optional hardware, which is a good thing. On the other hand things like SPI are no longer working. Raspbian tackles this with so called overlays and some help from the binary start.elf bootloader: 1. start.elf reads the dtb from the fat boot partition a) a file defined in config.txt, "device_tree=foo.dtb" b) a hardcoded hardware specific default file, "bcm2708-rpi-<variant>.dtb" 2. if the config.txt specifies "dtoverlay=foo-overlay" 1. the boot loader reads "overlays/foo-overlay.dtb" from the fat partition 2. the overlay is patched into the flattened device tree 3. the boot loader puts the device tree at address 0x100 (override with "device_tree_address=0xabcd1234" 4. the boot loader loads the specified kernel As openSUSE does not directly jump into the kernel, but starts u-boot, this does not work here. Issues: 1. u-boot does not have overlay support 2. u-boot loads its own dtb from storage, e.g. bcm2835-rpi-b.dtb 3. The u-boot boot.scr is loaded at address 0, and overwrites the boot loader provided dtb. The 3rd issue can be worked around with a "device_tree_address=0x1000" in config.txt. I tried to replace the "loadfdt" function in the boot.scr with a "fdt move 0x1000 0x2000000". Although the move succeeds, the kernel start crashes afterwards: ---- 4443840 bytes read in 1041 ms (4.1 MiB/s) 6946368 bytes read in 1403 ms (4.7 MiB/s) Copying FDT ... Kernel image @ 0x1000000 [ 0x000000 - 0x43cec0 ] data abort pc : [<17f63d68>] lr : [<17f644e0>] reloc pc : [<0001dd68>] lr : [<0001e4e0>] sp : 17b48a50 ip : 17b521e9 fp : 17f51c54 r10: 17f91354 r9 : 17b49ee8 r8 : 17f922bc r7 : 17f922b8 r6 : 17b521e0 r5 : 00000003 r4 : 33554432 r3 : 00000000 r2 : 00000010 r1 : 00000000 r0 : 33554432 Flags: nZCv IRQs off FIQs off Mode SVC_32 Resetting CPU ... ---- instead of: ---- 4443840 bytes read in 1268 ms (3.3 MiB/s) 6946368 bytes read in 1753 ms (3.8 MiB/s) 8127 bytes read in 56 ms (141.6 KiB/s) Kernel image @ 0x1000000 [ 0x000000 - 0x43cec0 ] ## Flattened Device Tree blob at 02000000 Booting using the fdt blob at 0x2000000 Using Device Tree in place at 02000000, end 02004fbe ---- So either this approach needs more work, or a completely different approach is needed to get overlays to work. Any ideas? Kind regards, Stefan -- Stefan Brüns / Bergstraße 21 / 52062 Aachen home: +49 241 53809034 mobile: +49 151 50412019 -- To unsubscribe, e-mail: [email protected] To contact the owner, e-mail: [email protected]
