Hi @all,
I'm trying to build a linux kernel as zImage and boot it with u-boot on
a qemu vexpress-a15 machine. The host machine is a Ubuntu 18.04.
What I tried until now:
1. Get Linux from git, export ARCH=arm and
CROSS_COMPILE=arm-linux-gnueabihf-
2. Make Defconfig: make vexpress_defconfig
3. Enable 'Early Printk' with make menuconfig
4. Make Kernel: make
5. Get U-Boot from git, export ARCH=arm and
CROSS_COMPILE=arm-linux-gnueabihf-
6. Make Defconfig: make vexpress_ca15_tc2_defconfig
7. Make U-Boot: make
8. Generate empty image file and mount it: truncate -s 100M image;
mkfs.ext4 image; mount -o loop image /mnt
9. Copy zImage and DTB to image: cp arch/arm/boot/zImage /mnt ; cp
arch/arm/boot/dts/vexpress-v2p-ca15_a7.dtb /mnt
10. Unmount Image: umount /mnt
11. Start u-boot in qemu: qemu-system-arm -m 1024M -M vexpress-a15 -cpu
cortex-a15 -kernel u-boot -serial stdio -sd image => U-Boot comes up and
I can hit a key to stop automount, ok so far
12. In u-boot, checking filesystem on image: ext4ls mmc 0:0 => I can see
my zImage and my DTB file, ok so far
13. In u-boot, loading kernel: ext4load mmc 0:0 82008000 zImage => XXXX
bytes read is shown, ok so far
14. In u-boot, loading DTB: ext4load mmc 0:0 85000000
vexpress-v2p-ca15_a7.dtb => YYYY bytes read, ok so far
15. In u-boot, boot: bootz 82008000 - 85000000 => 'Starting kernel ....'
and 'Uncompressing kernel done' is shown and then nothing at all...
Cross-checks I have done right now:
- Booting kernel and DTB directly from qemu with 'qemu-system-arm -m
1024M -M vexpress-a15 -cpu cortex-a15 -kernel arch/arm/boot/zImage -dtb
arch/arm/boot/dts/vexpress-v2p-ca15-tc1.dtb -serial stdio' works, normal
boot output is shown. Also the standard console device ttyAMA0 is
available after mounting devtmpfs.
- Same setup with vexpress-a9 (uboot with vexpress_ca9x4_defconfig,
linux with vexpress_defconfig and DTB vexpress-v2p-ca9.dtb. The kernel
was loaded to 62008000 and the DTB to 65000000) worked, Normal boot
output was shown.
What I don't understand right now is:
- Am I using the corrected DTB? vexpress-v2p-ca15-tc1.dtb or
vexpress-v2p-ca15_a7.dtb ? Which is the right one?
- What are the addresses I need to load kernel and the DTB? In the
working vexpress-a9 sample the kernel was loaded with a offset of
2008000h and the DTB with a offset of 5000000h to start of RAM at
60000000h. So I decided use the same offsets with the alternate start of
RAM address of 8000000h of vexpress-a15, i.e. kernel at 82008000 and DTB
at 85000000. Is this assumption correct?
- 'Starting kernel...' is a last message from u-boot and 'Uncompressing
kernel done' the first from the kernels self extractor?
- Where in RAM is the zImage decompressed by u-boot bootz? Between start
of RAM at 80000000h and kernels loadaddr at 82008000h?
- What are the differences between loading kernel and DTB by qemu
directly and loading kernel and DTB indirectly via u-boot?
Thank you very very much for your replies in advance.
Greetings,
André
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