Re: [microblaze-uclinux] Some questions

[John Williams <jwilliams@itee.uq.edu.au>]

Brett Boren wrote:
> What has to be changed to use the rest of the memory? Actually, I'm kinda
> confused how with only 13 address lines that you can even address 16MB.

Change the MHS to increase the address range, and change 
linux-2.4.x/include/asm-microblaze/mbvanilla.h:

/* Start and size of external RAM */
#define ERAM_ADDR 0x80000000
#define ERAM_SIZE 0x01000000

The DDR has two bank select lines to switch between the 4 banks, and the 
row and column addresses are muxed with the RAS and CAS lines.

>>Can you explain a bit more detail on this behaviour, when it happens,
>>when it doesn't etc?
> 
> The kernel and rc always finish booting. I can regularly make it happen
> immediately after rc stops executing. Since I never get the opportunity to
> use the shell I'm not sure I can provide any more info besides that kernel
> log below:

[snip]

hmm, this looks like a bug that I'm suffereing too - basically if the 
romfs image is greater than about 600K, the shell freezes soon after 
bootup.  I don't have a solution, but a workaround.

Basically you need to shrink your romfs, the easiest way to do this is 
add the following to the makefile in /vendors/..., under the image: target.

         for i in $(ROMFSDIR)/bin/* ; do \
                 $(CROSS)flthdr -z $$i; \
         done

This will basically compress all of the executables, down to about 50% 
original size, and is usualyl enough to squeak under this wierd bug. 
It's a problem I'm aware of, but haven't managed to track down the cause 
yet.

> When I was messing around with the  real linux kernel on my x86 box a little
> while ago we used a serial port to spit out the kernel log. Can we do that
> with the second serial line here?

I guess - the second serial port is just /dev/ttyS1, so you can write a 
script or application to open and write to it.

John

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