I am trying to get my own build of U-Boot to boot Linux on a Jetson TK1 board. As we are pushing for verified boot I am using the Flat Image Tree (unifying kernel image, device tree blob, ...) to describe my system. U-Boot can load the ITB file and tries to start the kernel but the system hangs after this message.
I assume that this is because no boot arguments are passed to the kernel (the original startup adds loads of arguments) but I am a little dumbfounded on how to pass the arguments to the kernel. I tried setting the bootargs environment variable but this did not change the situation.
How do I pass kernel arguments to the kernel when using an ITB file?
Command line arguments (taken from the APPEND command of the examples extlinux.conf):
console=ttyS0,115200n8 console=tty1 no_console_suspend=1
lp0_vec=2064@0xf46ff000 video=tegrafb mem=1862M@2048M memtype=255 ddr_die=2048M@2048M
section=256M pmuboard=0x0177:0x0000:0x02:0x43:0x00 vpr=151M@3945M tsec=32M@3913M
otf_key=c75e5bb91eb3bd947560357b64422f85 usbcore.old_scheme_first=1 core_edp_mv=1150
core_edp_ma=4000 tegraid=40.1.1.0.0 debug_uartport=lsport,3 power_supply=Adapter
audio_codec=rt5640 modem_id=0 android.kerneltype=normal usb_port_owner_info=0
fbcon=map:1 commchip_id=0 usb_port_owner_info=0 lane_owner_info=6 emc_max_dvfs=0
touch_id=0@0 tegra_fbmem=32899072@0xad012000 board_info=0x0177:0x0000:0x02:0x43:0x00
root=/dev/mmcblk0p1 rw rootwait tegraboot=sdmmc gpt
Content of ITS file:
/dts-v1/;
/ {
description = "Simple image with single Linux kernel and FDT blob";
#address-cells = <1>;
images {
kernel@1 {
description = "Vanilla Linux kernel";
data = /incbin/("./zImage");
type = "kernel";
arch = "arm";
os = "linux";
compression = "none";
load = <0x81008000>;
entry = <0x81008000>;
hash@1 {
algo = "crc32";
};
hash@2 {
algo = "sha1";
};
};
fdt@1 {
description = "Flattened Device Tree blob";
data = /incbin/("./tegra124-pm375.dtb");
type = "flat_dt";
arch = "arm";
compression = "none";
hash@1 {
algo = "crc32";
};
hash@2 {
algo = "sha1";
};
};
};
configurations {
default = "conf@1";
conf@1 {
description = "Boot Linux kernel with FDT blob";
kernel = "kernel@1";
fdt = "fdt@1";
};
};
};
U-Boot Output:
Tegra124 (Jetson TK1) # fatload mmc 1 0x90000000 /kernel_fdt.itb
reading /kernel_fdt.itb
5946200 bytes read in 497 ms (11.4 MiB/s)
Tegra124 (Jetson TK1) # bootm 0x90000000
## Loading kernel from FIT Image at 90000000 ...
Using 'conf@1' configuration
Verifying Hash Integrity ... OK
Trying 'kernel@1' kernel subimage
Description: Vanilla Linux kernel
Type: Kernel Image
Compression: uncompressed
Data Start: 0x900000ec
Data Size: 5910168 Bytes = 5.6 MiB
Architecture: ARM
OS: Linux
Load Address: 0x00000000
Entry Point: 0x00000000
Hash algo: crc32
Hash value: c5b4b377
Hash algo: sha1
Hash value: f001007efe83f563425bfe0659186a32395c946c
Verifying Hash Integrity ... crc32+ sha1+ OK
## Loading fdt from FIT Image at 90000000 ...
Using 'conf@1' configuration
Trying 'fdt@1' fdt subimage
Description: Flattened Device Tree blob
Type: Flat Device Tree
Compression: uncompressed
Data Start: 0x905a30ac
Data Size: 34678 Bytes = 33.9 KiB
Architecture: ARM
Hash algo: crc32
Hash value: e466b23e
Hash algo: sha1
Hash value: ec909ae16e62233d0ed1e1f4c909085abc9b5879
Verifying Hash Integrity ... crc32+ sha1+ OK
Booting using the fdt blob at 0x905a30ac
Loading Kernel Image ... OK
Using Device Tree in place at 905a30ac, end 905ae821
Starting kernel ...
The salient issue is that the system seems to hang after U-Boot outputs the text
Starting kernel ...
If an uncompressed kernel Image file has been loaded, then the actual kernel startup code would be executed next.
But if a uImage or zImage file has been loaded (which are also reported as "uncompressed" because they are self-extracting), then the next code executed would be the decompression routine that is attached to the zImage file. Normally this decompression routine will output text such as
Uncompressing Linux............ done, booting the kernel.
before the actual kernel startup code would be executed, before any processing of the kernel command line, before any processing of the Device Tree blob, and prior to any console output from the kernel (including earlyprintk).
There's a discrepancy between the kernel load & start addresses specified in the image header
Load Address: 0x00000000
Entry Point: 0x00000000
versus what is specified in the DT:
load = <0x81008000>;
entry = <0x81008000>;
Since the kernel image is temporarily loaded at
## Loading kernel from FIT Image at 90000000 ...
the addresses in the DT would seem to be correct, and the addresses in the image header are bogus.
Assuming that there is no physical RAM at 0x00000000, the result will be that the kernel image is copied (or decompressed) to the bogus load address of 0, and then the kernel image will be executed by branching to the bogus entry point of 0. The CPU is likely to hang trying to execute garbage from nonexistent memory, and that correlates perfectly with what you report.
Solution is (1) confirm that the kernel is linked to the correct address and (2) to specify the correct addresses in the mkimage command using the -a
and -e
command options.
This correction should at least get you past this one point.