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Diffstat (limited to 'Documentation/power/s2ram.txt')
| -rw-r--r-- | Documentation/power/s2ram.txt | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/Documentation/power/s2ram.txt b/Documentation/power/s2ram.txt index b05f512130e..1bdfa044377 100644 --- a/Documentation/power/s2ram.txt +++ b/Documentation/power/s2ram.txt @@ -49,8 +49,33 @@ machine that doesn't boot) is: 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 PLL's, and it just _hangs_. Using the regular VGA console and letting X resume it instead works fine. + +NOTE +==== +pm_trace uses the system's Real Time Clock (RTC) to save the magic number. +Reason for this is that the RTC is the only reliably available piece of +hardware during resume operations where a value can be set that will +survive a reboot. + +Consequence is that after a resume (even if it is successful) your system +clock will have a value corresponding to the magic number instead of the +correct date/time! It is therefore advisable to use a program like ntp-date +or rdate to reset the correct date/time from an external time source when +using this trace option. + +As the clock keeps ticking it is also essential that the reboot is done +quickly after the resume failure. The trace option does not use the seconds +or the low order bits of the minutes of the RTC, but a too long delay will +corrupt the magic value. |