Hi all Just want to post the resolution to the problem(s) causing the kernel code to reset the target.
on u-boot IMMR was set to 0x04700000, which is acceptable as far as u-boot is concerned, but not allowed once the kernel is initialised. The other issue was that the Chip Select was not configured properly on u-boot (2MB instead of 32MB), which was not noticed in u-boot since the u-boot never tried to access memory above that region, but caused the kernel to reset the target. I was still not able to debug the kernel (with gdb) before the kernel turned on the MMU, but since the kernel code is running past the MMU initialisation, I am now able to debug with source. I would also like to take this opportunity to thank all the people who replied to this post. Best regards Joao Vicente -----Original Message----- From: Joao Vicente Sent: Thursday, October 09, 2003 10:52 AM To: linuxppc-embedded at lists.linuxppc.org Subject: Problem debugging ppc kernel with DDD/GDB/BDI2000 on a custom MPC8260 board Hi I am trying to boot the ppc kernel on a MPC8260 based custom board. I am using the denx distribution linuxppc_2_4_devel, and I am configuring it using the TQM8260 default configuration, customising some CPM settings for UART and FEC. I have managed to port the u-boot loader for this board, and am at a stage where I am decompressing the kernel image onto the top of the RAM. I have debug enabled on the u-boot loader and the last line I see is ## Transferring control to Linux (at address 00000000) ... And then the board resets when allowed to run free, past this point. One of the doubts that I have is that when I look into the system.map file, it shows that the start address is at 0xc0000000 (as shown below) c0000000 T _start c0000000 T _stext c000000c T __start c000002c t __after_mmu_off c0000060 t turn_on_mmu c00000c4 T __secondary_hold c0000100 t Reset ... To the best of my knowledge the kernel image is not relocatable, so I am wondering if this could be my problem or just one of them ... Should the map file be showing 00000000 T _start ... If so, where should I change the .text address so that that happens ? I am also trying to debug the code from that address with gdb/BDI2000, but I am not getting very far. Basically I can see the program counter incrementing when I single step, but I cannot see the source even though I am trying to load the symbol table at 0x00000000 with the 'add-symbol-file vmlinux 0x00000000' gdb command, after invoking gdb from the kernel base directory (where vmlinux is) I also have tried to load the code with 'File|Open Program' command (I am using DDD), and then tried to execute the gdb 'target remote 10.121.10.22:2001' command, and I can see the code (head.S file) on my DDD code window, but the lines are not bound to any address, and I cannot follow the code when I try to step though it. Again does this not work because the code is not relocatable, or fo I need to use any additional compiler switches that are not switched on the default kernel configuration, or by any other reason I fail to see ? I would appreciate any help on this issue Thanks in advance Joao Vicente, Software Engineer. www.spectel.com ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/
