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Re: [Qemu-devel] [patch 0/2] Add flash emulation to the ARM Versatile PB

From: Thomas Petazzoni
Subject: Re: [Qemu-devel] [patch 0/2] Add flash emulation to the ARM Versatile PB platform
Date: Fri, 10 Oct 2008 16:52:24 +0200

Le Fri, 10 Oct 2008 16:02:52 +0200,
Jean-Christophe PLAGNIOL-VILLARD <address@hidden> a écrit :

> > > I suppose that if you propose such a change, you are using the
> > > flash with a bootloader in it. Could you please give us more
> > > details about it?
> > 
> > Sure. With these patches in place, I'm able to boot U-Boot in Qemu,
> > use TFTP to load a kernel, flash it, and boot it. I've detailed
> > what I've done at
> > http://thomas.enix.org/Blog-20081002153859-Technologie.
> > 
> > It works pretty well, except that I add to hack the CFG_HZ and timer
> > configuration values in U-Boot to get some same network timeout
> > values and such. Any help in this area would be appreciated.
> > 
> > If you want more details, I'll be glad to give them.
> I think I'll nice to add u-boot ML too and the ARM maintainer in copy
> maybe

Yes, maybe I should contact the U-Boot people. To get U-Boot to work on
the Versatile PB platform, I had to make several modifications to the
U-Boot configuration :

 * Switch to a custom versatile flash driver to the generic CFI driver.
   The custom versatile flash driver used by the default U-Boot
   versatile configuration doesn't play well with Qemu flash emulation
   for reasons that I haven't investigated.

   At least one people in 2005 sent patches to convert U-Boot versatile
   to use the generic CFI flash driver, but it seems that the patches
   haven't been integrated:

   I'd be glad to send the patch to the U-Boot people, but I couldn't
   test it on the hardware, so I'm not sure they work properly.

 * Switch to an external phy for the ethernet adapter. This works on
   Qemu, but probably won't work on the real hardware. But again, I
   couldn't test this on the hardware, so I'm not sure about posting a
   patch that I haven't been able to test.

 * Tune the CFG_HZ and CFG_TIMER_CTRL to get some sane timing
   behaviour. Here again, I wasn't able to test this on real hardware.
   And I don't even understand the new values, I just changed them
   until I found a combination that "worked".

Having a U-Boot configuration that works on Qemu would certainly be
nice, but I'm not sure how to proceed with these three problems. Any
hint maybe ?

Thanks !

Thomas Petazzoni, Free Electrons
Kernel, drivers and embedded Linux development,
consulting, training and support.

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