Basically, Iconia uses Atmel mxt1386 touchscreen controller. The same controller is used in Asus EEE Transformer and Motorola Xoom and even Samsung Galaxy Tab 10.1. So far, there are a lot of reports of EEE Transformer's and Xoom's touchscreens suddenly stopping working and starting working after a full battery discharge.
One day after a reboot my Iconia stopped booting - it keeped hanging on the Acer logo and when I tried entering recovery it was hanging at "booting recovery kernel image". However, that only happened with Acer kernels. With my own kernel, ported from EEE Transformer, the tablet could boot. I have recompiled the acer kernel with framebuffer console and found out it got stuck at the touchscreen interrupt handler while EEE's driver just printed an error and stopped working.. Basically, the response I got from from the touchscreen was [1, 0x80, 0, 0, 0, 0, 0, 0]. And it was not detected with i2cdetect
At first, I thought my touchscreen cable was damaged. I have disassembled the tablet and tried twisting the cable to see if it gives any result. My result was that if I disconnect and reconnect the cable, an interrupt comes. Btw, the cable has sharp 'teeth' and you can crimp it pretty much like ethernet.
Ok, so then I added some printks to the driver. Turns out, when some data coming from the touchscreen was incorrect, the driver hanged (deadlocked) because the semaphore was pushed down two times and never upped. So, I have commented out semaphores and bingo - it continued booting. Although there were a lot of warn_slowpath errors and CRC error, it reported correct coordinates. I flashed Acer's kernel after it and it booted fine. Looks like a proper init by Acer driver reset the controller.
The archive in the link contains tegra i2c driver from the chromium tree (in case it finds i2c errors like nak, it retries the transmission several times) and the touchscreen driver. You need to comment out "#define USE_SEMA" to disable semaphores and build the kernel with it in case you encounter the problem..
I do not have another 'brick' to test if my solution works in all cases but I'm just leaving the stuff here in case anyone faces the trouble. To flash when your tablet is not booting you'll probably some help from sc2k..
What's the moral of the story? The moral is that as touchscreen is not used in recovery, it may be a good idea to add the 'hacked and buggy' driver to the recovery kernel to allow to recover the device by just booting recovery in case anyone faces the problem.. Of course it's better to fix the driver properly or even use the driver from mainline linux and patch it.
here is a link to the cwm recovery image with the 'hacked' driver. Boots just fine.