screen dumps, done in style

[Werner Almesberger]

Today, I needed a screen dump from u-boot, and I though I'd give the
JTAG approach a try again. We experimented with this a long time ago
on GTA01, but it never worked, so I didn't have much hope.
Surprisingly, this worked in the first try on GTA02.

Here's how it's done:

OpenOCD:
> dump_image dump.scr 0x8800000 0x96000

Host:
% cd svn.openmoko.org/developers/werner
% ./scr2ppm.pl /where/ever/dump.scr >dump.ppm

Note that the dumping only works like this if the frame buffer is
identity-mapped. Under Linux, it ends up at a different address. Also,
my GTA01v4 still doesn't like this way of doing screen dumps. (JTAG
fails with "timeout waiting for SYSCOMP & DBGACK".)

- Werner