Re: [PATCH v2] PCI / PM: Allow runtime PM without callback functions

[Jarkko Nikula <jarkko.nikula@linux.intel.com>]

Hi

On 10/25/18 4:57 PM, Rafael J. Wysocki wrote:
> On Tue, Oct 23, 2018 at 1:46 PM Jarkko Nikula
> <jarkko.nikula@linux.intel.com> wrote:
>>
>> Commit a9c8088c7988 ("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 causes that SMBus PCI device stays in D0 power state and sysfs
>> /sys/bus/pci/devices/[SMBus PCI ID]/power/runtime_status shows "error"
>> when the runtime PM framework attempts to autosuspend the device. This
>> is due PCI bus runtime PM which checks for driver runtime PM callbacks
>> and returns with -ENOSYS if they are not set.
>>
>> Since i2c-i801.c don't need to do anything device specific beyond PCI
>> device power state management Jean Delvare proposed if this can be fixed
>> in the PCI subsystem core level rather than adding dummy runtime PM
>> callback functions in the PCI drivers.
>>
>> Change the pci_pm_runtime_suspend()/pci_pm_runtime_resume() semantics so
>> that they allow change the PCI device power state during runtime PM
>> transitions even if no runtime PM callback functions are defined.
>>
>> This change fixes the runtime PM regression on i2c-i801.c.
>>
>> It is not obvious why the code had hard requirements for the runtime PM
>> callbacks. Test has been here since the code was introduced by the
>> commit 6cbf82148ff2 ("PCI PM: Run-time callbacks for PCI bus type").
>>
>> On the other hand similar change than this was done to generic runtime
>> PM callbacks way back in the commit 05aa55dddb9e ("PM / Runtime: Lenient
>> generic runtime pm callbacks").
>>
>> Fixes: a9c8088c7988 ("i2c: i801: Don't restore config registers on runtime PM")
>> Reported-by: Mika Westerberg <mika.westerberg@linux.intel.com>
>> Cc: <stable@vger.kernel.org> # 4.18+
>> Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
> 
> Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> 
I guess this patch with Reviewed-by tags from Rafael and Jean got buried 
under other list traffic as I don't find this from pci.git or linux-next?

-- 
Jarkko