Bug#588602: Bug#: 588601, 588602: xpress 200m 5955 => resume from suspend fails with KMS enabled
I dedicated a large portion of the day to finding a clue to this one. Following this advice:*http://lxr.linux.no/#linux+v220.127.116.11/Documentation/power/s2ram.txt
I was able to extract a trace from the failed resume process:
Magic number: 0:981:799hash matches drivers/base/power/main.c:523pci 0000:01:05.0: hash matchesec PNP0C09:00: hash matches
The first hash match is none other than my ATI Radeon card as I easily verified with lspci:
01:05.0 VGA compatible controller: ATI Technologies Inc Radeon XPRESS 200M 5955 (PCIE)
However, the above link says that the likely culprit in the failed resume process is the last hash match. This corresponds to the EC driver:*http://lxr.free-electrons.com/source/drivers/acpi/ec.c
My card was, till recently, listed under embedded graphics at the AMD/ATI website. So there appears to be some conflict when using KMS between radeon and ec that causes the kernel to hang (that explains why I can't ssh into my computer to get a trace). For this reason I've cloned the original bug and reported the copy as a kernel bug.
I will try to delve deeper into the matter by activating more verbose debugging symbols for acpi.
I would appreciate some advice and guidance, since I'm flying half-blind (I will try to follow the information present here*http://ubuntuforums.org/showthread.php?t=505890)