• Rafael J. Wysocki's avatar
    PCI / ACPI / PM: Resume bridges w/o drivers on suspend-to-RAM · 26112ddc
    Rafael J. Wysocki authored
    It is reported that commit c62ec461 (PM / core: Fix direct_complete
    handling for devices with no callbacks) introduced a system suspend
    regression on Samsung 305V4A by allowing a PCI bridge (not a PCIe
    port) to stay in D3 over suspend-to-RAM, which is a side effect of
    setting power.direct_complete for the children of that bridge that
    have no PM callbacks.
    
    On the majority of systems PCI bridges are not allowed to be
    runtime-suspended (the power/control sysfs attribute is set to "on"
    for them by default), but user space can change that setting and if
    it does so and a given bridge has no children with PM callbacks, the
    direct_complete optimization will be applied to it and it will stay
    in suspend over system suspend.  Apparently, that confuses the
    platform firmware on the affected machine and that may very well
    happen elsewhere, so avoid the direct_complete optimization for
    PCI bridges with no drivers (if there is a driver, it should take
    care of the PM handling) on suspend-to-RAM altogether (that should
    not matter for suspend-to-idle as platform firmware is not involved
    in it).
    
    Fixes: c62ec461 (PM / core: Fix direct_complete handling for devices with no callbacks)
    Link: https://bugzilla.kernel.org/show_bug.cgi?id=199941
    Reported-by: n0000b.n000b@gmail.com
    Tested-by: n0000b.n000b@gmail.com
    Reviewed-by: default avatarMika Westerberg <mika.westerberg@linux.intel.com>
    Acked-by: default avatarBjorn Helgaas <bhelgaas@google.com>
    Cc: 4.15+ <stable@vger.kernel.org> # 4.15+
    Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
    26112ddc
pci-acpi.c 22.6 KB