On 10/19/2018 12:25 AM, Bjorn Helgaas wrote:
On Thu, Oct 18, 2018 at 03:30:38PM +0300, Jarkko Nikula wrote:
Allow PCI core to do runtime PM to devices without needing to use dummy
runtime PM callback functions if there is no need to do anything device
specific beyond PCI device power state management.
Implement this by letting core to change device power state during
runtime PM transitions even if no callback functions are defined.
Fixes: a9c8088c7988 ("i2c: i801: Don't restore config registers on runtime PM")
Reported-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
I applied this with Rafael's reviewed-by to pci/misc for v4.20,
thanks!
But I dropped the stable tag because if I understand correctly, the
point of this is to avoid the need for SIMPLE_DEV_PM_OPS() in drivers
that don't need to do anything for PM.
That's worthwhile, but it's not transparently obvious that it would
qualify for a stable backport based on this:
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/stable-kernel-rules.rst
If there's an argument for adding a stable tag, I'll add it , but that
justification should be explicit in the changelog.
No disagreement here. I was thinking a second or two before sending the
patch may I Cc or not the stable. I went adding it since this actually
fixes a PM regression on i2c-i801 after v4.18. SMBus PCI device doesn't
go to D3 and
/sys/bus/pci/devices/[0000:00:1f.3 etc]/power/runtime_status
shows "error" when runtime PM framework attempts to autosuspend the device.
But given that most of the platforms I have seen don't implement the PM
capabilities for SMBus PCI device, a few do implement though, and we
haven't got any regression reports either so this is not very fatal IMHO.
I definitely don't want to see massive regression from different PCI
systems either. Queueing for v4.20 sounds reasonable and we can ask to
cherry-pick the commit into v4.18 and v4.19 stable kernels if nothing
fatal shows up.
--
Jarkko
