• Jarkko Nikula's avatar
    PCI / PM: Allow runtime PM without callback functions · c5eb1190
    Jarkko Nikula authored
    a9c8088c ("i2c: i801: Don't restore config registers on runtime PM")
    nullified the runtime PM suspend/resume callback pointers while keeping the
    runtime PM enabled.
    This caused the SMBus PCI device to stay in D0 with
    /sys/devices/.../power/runtime_status showing "error" when the runtime PM
    framework attempted to autosuspend the device.  This is due to PCI bus
    runtime PM, which checks for driver runtime PM callbacks and returns
    -ENOSYS if they are not set.
    Since i2c-i801.c doesn't need to do anything device-specific for runtime
    PM, Jean Delvare proposed this be fixed in the PCI core rather than adding
    dummy runtime PM callback functions in the PCI drivers.
    Change pci_pm_runtime_suspend()/pci_pm_runtime_resume() so they allow
    changing the PCI device power state during runtime PM transitions even if
    the driver supplies no runtime PM callbacks.
    This fixes the runtime PM regression on i2c-i801.c.
    It is not obvious why the code previously required the runtime PM
    callbacks.  The test has been there since the code was introduced by
    6cbf8214 ("PCI PM: Run-time callbacks for PCI bus type").
    On the other hand, a similar change was done to generic runtime PM
    callbacks in 05aa55dd ("PM / Runtime: Lenient generic runtime pm
    Fixes: a9c8088c
     ("i2c: i801: Don't restore config registers on runtime PM")
    Reported-by: default avatarMika Westerberg <mika.westerberg@linux.intel.com>
    Signed-off-by: default avatarJarkko Nikula <jarkko.nikula@linux.intel.com>
    Signed-off-by: default avatarBjorn Helgaas <bhelgaas@google.com>
    Reviewed-by: default avatarJean Delvare <jdelvare@suse.de>
    Reviewed-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
    Cc: stable@vger.kernel.org	# v4.18+