[U-Boot] MPC8315 uboot hangs on relocation
Hi All,
I am porting the u-boot for a customized board based on MPC8315 processor. It has DDR2 SDRAM of 128 MB & 8 MB of flash. I found that the code hangs during the relocation of the code, exactly in the following line (@ relocation function in cpu/mpc83xx/start.S) lwz r5, GOT(__bss_start)
Since the board has only 8MB of flash, I have modified the the TEXT_BASE to 0xFFF80000(as against 0xFE000000). I am able to access the DDR2 SDRAM(whole 128MB) , I tested it by writing & reading the patterns 0xaaaaaaaa & 0x555555555, So I assumed the DDR2 SDRAM timing are proper.
I would like to know the following 1. What does the 'GOT(__bss_start) do? 2. Do I have to change the linker script since I have changed the TEXT_BASE? 3. Is there any other cause for hanging?
Thank you in advance for helping Regards, Suresh
Dear Sureshkumar Nagarathinam,
In message 839118.2412.qm@web112320.mail.gq1.yahoo.com you wrote:
Since the board has only 8MB of flash, I have modified the the TEXT_BASE to 0xFFF80000(as against 0xFE000000). I am able to access the DDR2 SDRAM(whole 128MB) , I tested it by writing & reading the patterns 0xaaaaaaaa & 0x555555555, So I assumed the D DR2 SDRAM timing are proper.
This is absolutely NO guarantee that the RAM is working correctly at all. You did not try any burst mode accesses. See the FAQ: http://www.denx.de/wiki/view/DULG/UBootCrashAfterRelocation
I would like to know the following
- What does the 'GOT(__bss_start) do?
It's the entry of __bss_start in the GOT (Global Offset Table). But you don't need to know this. It is unrelated to your problem.
- Do I have to change the linker script since I have changed the TEXT_BASE?
Are you sure you understood exactly what you changed, and why?
- Is there any other cause for hanging?
RAM not correctly initialized.
Best regards,
Wolfgang Denk
Sureshkumar Nagarathinam wrote:
Hi All,
I am porting the u-boot for a customized board based on MPC8315 processor. It has DDR2 SDRAM of 128 MB & 8 MB of flash. I found that the code hangs during the relocation of the code, exactly in the following line (@ relocation function in cpu/mpc83xx/start.S) lwz r5, GOT(__bss_start)
Besides what Wolfgang wrote, are you sure you have your memory map set up properly so GOT(__bss_start) is mapped to a valid piece of memory? If your memory map is not configured properly, you might be getting a double bus fault (first fault due to unmapped memory, second fault due to the bus fault vector causing a bus fault), causing the processor to curl up and die.
Depending on processor, processor configuration, and phase of the moon, sometimes it is actually the next instruction that is causing the bus fault because the processor can prefetch and speculatively execute instructions. Probably not in this case, but be warned.
[snip]
Thank you in advance for helping Regards, Suresh
Good luck, gvb
participants (3)
-
Jerry Van Baren -
Sureshkumar Nagarathinam -
Wolfgang Denk