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Date: Sat, 10 Aug 2013 16:31:02 +0400
From: Solar Designer <solar@...nwall.com>
To: Sylvain Munaut <246tnt@...il.com>
Cc: john-dev@...ts.openwall.com
Subject: Re: FPGA reprogramming on ZedBoard / Parallella board

Sylvain,

On Sat, Aug 10, 2013 at 12:02:06PM +0200, Sylvain Munaut wrote:
> When you say "Ethernet stops working". Are you sure the cpu still runs
> and it didn't crash ?

No.

> Can you use the serial console and still interact with the on-board linux ?

Frankly, I've been lazy to test that so far (in these bitstream
experiments this week; I've used the serial console to troubleshoot and
fix an unrelated issue before).  Will do.

> Or is it possible the whole PS system crashed ?

This is possible.

> Currently my thought would be that the whole CPU crashes because the
> new bitstream you're loading doesn't have the peripheral expected to
> be present for the given device tree. When you boot with the system
> that was shipped originally on the SD card (which is different from
> the files on the ftp!), it boots to a linux desktop and has hdmi and
> audio support and some other stuff that are all implemented in the PL.
> If you then load a bitstream that doesn't have those in the PL, the
> loaded drivers could try to issue bus requests that will go unanswered
> and just crash / kernel panic ...

This may well be the case.

How do we generate a bitstream that would have all components that
Parallella's default bitstream does?

Alternatively, we'd need to somehow reduce the Linux system's dependency
on available peripherals.  The quickest thing to try may be killing the
X server before loading the new bitstream - then hopefully the lack of
HDMI won't matter.  If this is not enough, then I'm afraid we may have
to update BOOT.BIN, so that the Linux kernel does not see any
peripherals that would not be available with our new bitstream.
"lsmod" shows that no modules are loaded, so we're out of luck unloading
any drivers.

Thanks,

Alexander

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