PM: Add sysfs attr for rechecking dev hash from PM trace
If the device which fails to resume is part of a loadable kernel module
it won't be checked at startup against the magic number stored in the
RTC.
Add a read-only sysfs attribute /sys/power/pm_trace_dev_match which
contains a list of newline separated devices (usually just the one)
which currently match the last magic number. This allows the device
which is failing to resume to be found after the modules are loaded
again.
Signed-off-by: James Hogan <james@albanarts.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
diff --git a/Documentation/power/s2ram.txt b/Documentation/power/s2ram.txt
index 514b94f..1bdfa04 100644
--- a/Documentation/power/s2ram.txt
+++ b/Documentation/power/s2ram.txt
@@ -49,6 +49,13 @@
device (lspci and /sys/devices/pci* is your friend), and see if you can
fix it, disable it, or trace into its resume function.
+ If no device matches the hash (or any matches appear to be false positives),
+ the culprit may be a device from a loadable kernel module that is not loaded
+ until after the hash is checked. You can check the hash against the current
+ devices again after more modules are loaded using sysfs:
+
+ cat /sys/power/pm_trace_dev_match
+
For example, the above happens to be the VGA device on my EVO, which I
used to run with "radeonfb" (it's an ATI Radeon mobility). It turns out
that "radeonfb" simply cannot resume that device - it tries to set the