Jerry Van Baren wrote:
Alan Bennett wrote:
Help; I'm trying to figure out if these errors are hardware or software. And of course, this is our first ppc/uboot system, so I'm still stepping through a lot of learning as I go.
I'm supposed to have a memory region from 0 to 7fff_ffff assigned to
Looks like 07ff_ffff to me, although it doesn't matter for this discussion.
our 128MB memory. However, I run into several issues when trying to run mtest. I end up with an large sections mis-behaving. I don't see any conflicts in the BRx registers, and I believe my OR1 is set up properly, so I'm not sure how to proceed.
good: #> md 0x00100000 1; mw 0x00100000 0xfff0000f ; md 0x00100000 1; 00100000: ffffffff .... 00100000: fff0000f ....
bad: #> md 0x00b8ac98 1; mw 0x00b8ac98 0xffff0000 ; md 0x00b8ac98 1; 00b8ac98: 61633938 ac98 00b8ac98: 61633938 ac98
OK, the *data bits* in the memory are the *ASCII* values that form the lower half of the address 0x61 = 'a', 0x63 = 'c', 0x39 = '9', 0x38 = '8'. There is *no way* this can be a coincidence unless you wrote those values in intentionally before doing the above example "mw" command. Going down that decision tree...
a) If you put 0x61633938 in that location of memory, how did you do it when it worked as opposed to the above illustration where it failed?
b) If you *didn't* put 0x61633938 in that memory location, who did? There is no way hardware mis-wrote half the address as *ASCII* values as part of the "mw" command which means either there is a software bug involved or your hardware is seriously sick (does u-boot run reliably?). If this is the case, what happens when you use capital letter addresses? md 0x00b8AC98 1; mw 0x00b8AC98 0xffff0000 ; md 0x00b8AC98 1;
Hi Alan,
[snip]
The above symptoms could be because your u-boot scratchpad memory (.data and/or .bss) resides in the memory locations you are trying to test - 0x00b8xxxx - either intentionally or unintentionally. If unintentionally, you have either a hardware problem or a software misconfiguration.
Is your memory space clean or does it get replicated? If you write a unique pattern (say 0xcafeface) to address 0x0000_0000, do you see it again at an address related by one address bit - e.g. 0x0400_0000, 0x0200_0000, 0x0100_0000, ... 0x0000_0010, 0x0000_0008, 0x0000_0004?
Hardware problems would tend to be miswiring or shorts/opens on the address bus. That would be Very Bad. :-(
Software problems would tend to be errors in SDRAM (DDR/DDR2) configuration - if, for instance, you have your processor initialized with the wrong address split on the bank select, you will be sending the wrong number of bits for RAS and CAS, causing a memory "duplication" problem. That would not be good, but *NOT* Very Bad since it is dead simple to fix (once you figure out what the configuration _should_ be, that is ;-).
Good luck, gvb