Re: [microblaze-uclinux] Some questions

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

Hi Brett,

> Why is it that /proc/mounts contains all of the mounted fs's in the 
> demo, but I never can get it to show mounts on my kernels?

That's a good question - now that you mention it I see the same thing, 
but don't know why it has happened or what has caused the change.  I'll 
look into it and see what I can find.

> What is the usage (in mbvanilla) and layout of memory devices? 

There is 16MByte of DDR mapped at 0x80000000, 8MB flash mapped at 
0xff000000 and 1MB of SRAM mapped at 0xffe00000.  The SRAM is not 
currently used in my build.

> What parts of the fs are writable? 

In my setup /var and /usr are mount points, where ext2-based ramdisks 
are mounted on bootup.  The rest of the filesystem is read only.

> Where is that ramfs stored?
The root filesystem is stored in RAM, immediately after the kernel BSS 
segment.  It is copied there by the early setup code 
arch/microblaze/kernel/mbvanilla.c - mach_early_init().

note the root filesystem is of type romfs, meaning that even though it 
is stored in RAM, it is not writeable.  That's what the /usr and /var 
mount points there for.

> How big is the DDR chip on the Memec board (I was under the impression 
> that it was 32MB, but the kernel reports differently)?

Hmmm..  I lifted the DDR controller parameters straight from an Insight 
reference design (which used the DDR range 0xfe000000 to 0xfeffffff ie 
16Mbyte).  However, the DDR datasheet states that the device is a 
4Mx4banksx16 bits device = 32Mbyte...

So there might be a cheap and simple memory upgrade in there... :)

> Next, I've got a problem with my board locking up (flashing LED stops) 
> when being used with a network-enabled kernel. I have attached the 
> .configs associated with this kernel.

Can you explain a bit more detail on this behaviour, when it happens, 
when it doesn't etc?

> Probably a small issue, but I can't get dhcpcd to work. I see on my dhcp 
> server where an IP is assigned to the MAC, but the command never returns.

I haven't really investigated the dhcp support yet, you may need to just

> Lastly, does anyone know of some embedded benchmarks they'd recommend? I 
> need some that are reputable enough to use in a comparison study that I 
> plan to publish.

There's a dhrystone application in the uclinux-dist, but the only time I 
tried running it didn't seem to do what I expected - I have no idea if 
it's considered uClinux-safe..

Regards,

John

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