Hi all,
I'm stuck trying to get Linux to boot from U-Boot on a Coldfire system and I'd love some ideas of what to try next.
I'm upgrading a uClinux system from a 2.4 kernel to 3.3. Additionally I'm trying to upgrade the boot-loader from u-boot 1.1.6 to release 2012.07. The board is based on a MCF5235EVB. I did the Linux upgrade first, and am successfully getting the existing system boot loader to boot my upgraded Linux 3.3 images. Now I've moved on to upgrading u-boot.
I was able to get U-Boot to come up successfully and it recognizes my Linux image and a bootm command starts just fine. It does the checks, uncompresses, and goes to boot. I turned on the debug messages in U-Boot, so I get the "## Transferring control to Linux (at address 0x20000) ..." message, it goes and does the jump and then...nothing...
Note that the exact same Linux image boots fine from 1.1.6. My 1.1.6 can boot both the 2.4 legacy image as well as my new 3.3 image.
Unfortunately I've got minimal visibility into the system (My BDM interface is being a PITA, I've got assembly-only stepping, using CodeWarrior!!@#!@$!, in flash only. Pretty much nothing else other than flash access is functioning right with the BDM at the moment), so I've been relegated to debug-via-printf, which isn't terribly useful at the interface between u-boot and linux.
Through reading code, I see a huge discrepancy between how 1.1.6 and 2012.07 starts the kernel.
1.1.6 uses a line: theKernel (linux_argc, linux_argv, linux_env, 0);
2012.07: /* * Linux Kernel Parameters (passing board info data): * sp+00: Ignore, side effect of using jsr to jump to kernel * sp+04: ptr to board info data * sp+08: initrd_start or 0 if no initrd * sp+12: initrd_end - unused if initrd_start is 0 * sp+16: Start of command line string * sp+20: End of command line string */ (*kernel) (kbd, initrd_start, initrd_end, cmd_start, cmd_end);
Clearly different... I'd assume that U-Boot's Linux starting magic is in sync with the current Linux kernel, but if that's the case, and these are actually as different as they appear, then the OLD U-Boot should have a problem starting the NEW kernel also. For grins, I grafted on the old sequence code into the new U-Boot, but that (as expected) failed also.
I looked at the Coldfire startup code in Linux and it looks like it corrosponds to the same comment in U-Boot, and interestingly it seems to discard the bd_t structure that's passed in first.
So far I think I've figured this out: * The FDT isn't used on Coldfire targets. * The Coldfire code discards the bd_t data passed in through u-boot. * Something funky is going on keeping Linux from booting, and it happens early enough that I can't see it on the console.
If it makes a difference, for some reason we load kernel at 0x20000 and jump to 0x20000. This is a legacy of the existing project, I've tried to change it to 0x0, but that didn't help either. I had suspected it had to do with where the old bootloader placed itself in RAM, but it shouldn't be an issue with the new bootloader.
For reference: RAM: 0x00000000, 32MB SRAM: 0x20000000 MBAR: 0x40000000 Flash: 0xFFC00000, 4mb (second flash module at 0xFF800000, but U-Boot doesn't know about that one). Image is stored at 0xFFC40000 and uses an initrd romfs immedately after the kernel
Basic setup and design is similar to the 5235EVB.
CONFIG_UBOOT, MTD_UCLINUX and MTD_UCLINUX_EBSS are all Y.
I've been bashing my head against this wall all week, so I'd love it if anyone's got some ideas.
Thanks, - Steve
5235IWI> bootm 0xffc40000 ## Current stack ends at 0x01f2ca2c * kernel: cmdline image address = 0xffc40000 ## Booting kernel from Legacy Image at ffc40000 ... Image Name: IWI 007 Image Type: M68K Linux Kernel Image (gzip compressed) Data Size: 2270515 Bytes = 2.2 MiB Load Address: 00020000 Entry Point: 00020000 Verifying Checksum ... OK kernel data at 0xffc40040, len = 0x0022a533 (2270515) ## No init Ramdisk ramdisk start = 0x00000000, ramdisk end = 0x00000000 Uncompressing Kernel Image ... OK kernel loaded at 0x00020000, end = 0x00470404 ## cmdline at 0x01f2c520 ... 0x01f2c520 ## kernel board info at 0x01f2c4e0 memstart = 0x00000000 memsize = 0x02000000 flashstart = 0xFFC00000 flashsize = 0x00400000 flashoffset = 0x00000000 sramstart = 0x20000000 sramsize = 0x00010000 mbar = 0x40000000 cpufreq = 150 MHz busfreq = 75 MHz baudrate = 57600 bps ## initrd_high = 0xffffffff, copy_to_ram = 1 ramdisk load start = 0x00000000, ramdisk load end = 0x00000000 ## Transferring control to Linux (at address 00020000) ...