On Thu, Nov 24, 2011 at 09:09:38PM +0100, Robert Jarzmik wrote:
> Sascha Hauer <s.hauer@xxxxxxxxxxxxxx> writes:
> > I remember Marc had some trouble with the mmu/cache implementation on
> > PXA. I don't know the details though. Maybe you have to dig through
> > the manuals/kernel code to find out the differences between the normal
> > arm v5 and pxa.
>
> Ah, I know what happens now, and it's tricky.
> First of all, you're right, there's a flat uncached mapping, I was misled by
> the function name "create_section", without looking closely at it. I thought
> it created the first section, not all the 4096 1MBytes section of a 4GB
> address space.
> It would deserve a "create_sections" name, in plural form.
Agreed.
>
> Now, for the serial UDC not working, there comes the fun.
> What's happening is that I'm using a default environment, with the init
> script in [1]. This script has an error somewhere.
> In barebox_startup(), we have :
> if (!stat("/env/bin/init", &s)) {
> run_command("source /env/bin/init", 0);
>
> And here is the trickery:
> - in the NOMMU case, the run_command() returns, and the code continues to the
> eternal loop of run_shell(), which calls console.getc(), which calls
> poller(), which call the UDC poll method
> => the gadget does work
> => I have a console, hurray !
>
> - in the MMU case, the run_command() never returns, and the poller method is
> never called. I traced that with my leds.
> => the gadget does *not* work
>
> So the problem was not the IO mapping, but a difference in run_command() between
> MMU and non-MMU config. Moreover, in non-MMU case, once my console is connected,
> I see a message :
> > running /env/bin/init...
> > syntax error
> I the MMU case, as the gadget doesn't work, I'm blind, so I can't really tell
> what is happening and which is the impact of MMU over run_command()...
Hmmm...
I just made your patches work on my pcm027 board (If you haven't fixed
the serial driver already: now I have patches for this). Without MMU
everything is fine. With MMU I had to disable the zero page because
otherwise the cfi flash driver will bail out with a NULL pointer deref.
With this I noticed that when I start barebox from U-Boot that the
driver does not recognize the flash. The following code from
arch/arm/boot/compressed/head-xscale.S helped:
@ Preserve r8/r7 i.e. kernel entry values
@ Data cache might be active.
@ Be sure to flush kernel binary out of the cache,
@ whatever state it is, before it is turned off.
@ This is done by fetching through currently executed
@ memory to be sure we hit the same cache.
bic r2, pc, #0x1f
add r3, r2, #0x10000 @ 64 kb is quite enough...
1: ldr r0, [r2], #32
teq r2, r3
bne 1b
mcr p15, 0, r0, c7, c10, 4 @ drain WB
mcr p15, 0, r0, c7, c7, 0 @ flush I & D caches
@ disabling MMU and caches
mrc p15, 0, r0, c1, c0, 0 @ read control reg
bic r0, r0, #0x05 @ clear DC, MMU
bic r0, r0, #0x1000 @ clear Icache
mcr p15, 0, r0, c1, c0, 0
I don't know what's going on here.
Sascha
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