• Rafael J. Wysocki's avatar
    swsusp: introduce restore platform operations · a634cc10
    Rafael J. Wysocki authored
    At least on some machines it is necessary to prepare the ACPI firmware for the
    restoration of the system memory state from the hibernation image if the
    "platform" mode of hibernation has been used.  Namely, in that cases we need
    to disable the GPEs before replacing the "boot" kernel with the "frozen"
    kernel (cf.  http://bugzilla.kernel.org/show_bug.cgi?id=7887).  After the
    restore they will be re-enabled by hibernation_ops->finish(), but if the
    restore fails, they have to be re-enabled by the restore code explicitly.
    
    For this purpose we can introduce two additional hibernation operations,
    called pre_restore() and restore_cleanup() and call them from the restore code
    path.  Still, they should be called if the "platform" mode of hibernation has
    been used, so we need to pass the information about the hibernation mode from
    the "frozen" kernel to the "boot" kernel in the image header.
    
    Apparently, we can't drop the disabling of GPEs before the restore because of
    Bug #7887 .   We also can't do it unconditionally, because the GPEs wouldn't
    have been enabled after a successful restore if the suspend had been done in
    the 'shutdown' or 'reboot' mode.
    
    In principle we could (and probably should) unconditionally disable the GPEs
    before each snapshot creation *and* before the restore, but then we'd have to
    unconditionally enable them after the snapshot creation as well as after the
    restore (or restore failure)   Still, for this purpose we'd need to modify
    acpi_enter_sleep_state_prep() and acpi_leave_sleep_state() and we'd have to
    introduce some mechanism synchronizing the disablind/enabling of the GPEs with
    the device drivers' .suspend()/.resume() routines and with
    disable_/enable_nonboot_cpus().   However, this would have affected the
    suspend (ie.  s2ram) code as well as the hibernation, which I'd like to avoid
    in this patch series.
    Signed-off-by: default avatarRafael J. Wysocki <rjw@sisk.pl>
    Cc: Nigel Cunningham <nigel@nigel.suspend2.net>
    Cc: Pavel Machek <pavel@ucw.cz>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    a634cc10
power.h 5.85 KB