The patch titled
pm: document use of RTC in pm_trace
has been added to the -mm tree. Its filename is
pm-document-use-of-rtc-in-pm_trace.patch
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------------------------------------------------------
Subject: pm: document use of RTC in pm_trace
From: Frans Pop <elendil@xxxxxxxxx>
As pm_trace uses the system's hardware clock to save its magic value,
users of that option should be warned that using this debug option will
result in an incorrect system time after resume.
Signed-off-by: Frans Pop <elendil@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/power/s2ram.txt | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff -puN Documentation/power/s2ram.txt~pm-document-use-of-rtc-in-pm_trace Documentation/power/s2ram.txt
--- a/Documentation/power/s2ram.txt~pm-document-use-of-rtc-in-pm_trace
+++ a/Documentation/power/s2ram.txt
@@ -54,3 +54,21 @@ used to run with "radeonfb" (it's an ATI
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 mumber 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.
_
Patches currently in -mm which might be from elendil@xxxxxxxxx are
e1000e-avoid-duplicated-output-of-device-name-in-kernel-warning.patch
e1000e-avoid-duplicated-output-of-device-name-in-kernel-warning-checkpatch-fixes.patch
e1000e-avoid-duplicated-output-of-device-name-in-kernel-warning-fix.patch
e100-adapt-to-the-reworked-pci-pm.patch
mm-page_allocc-free_area_init_nodes-fix-inappropriate-use-of-enum.patch
pm-document-use-of-rtc-in-pm_trace.patch
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