Re: [PATCH v5 0/4] PCI: Add support for suspending (including runtime) of PCIe ports

[Mathias Nyman <mathias.nyman@intel.com>]

On 29.04.2016 11:51, Mika Westerberg wrote:
> Current Linux PCI core does not do any kind of power management to PCIe
> ports. This means that we waste energy and consume laptop battery even if
> the port has nothing connected to. These patches aim to change that to the
> right direction.
>
> Previous versions of the patches can be found below:
>
>    v1: http://www.spinics.net/lists/linux-pci/msg49313.html
>    v2: http://www.spinics.net/lists/linux-pci/msg50167.html
>    v3: http://www.spinics.net/lists/linux-pci/msg50345.html
>    v4: http://www.spinics.net/lists/linux-pci/msg50665.html
>
> This assumes that recent (starting from 2015) PCIe ports are capable of
> transition to D3hot/D3cold. We add a new flag to struct pci_dev 'bridge_d3'
> that is set whenever the PCI core thinks the port can be put to D3. The
> check in pci_pm_suspend_noirq() is then extended to cover devices where
> 'bridge_d3' is set.
>
> We then add two new functions pci_bridge_d3_device_changed/removed(). These
> are used to set and clear 'bridge_d3' whenever there is a change in device
> power management policy (or if the device is removed). For example when
> userspace forbids the device to enter D3cold pci_bridge_d3_device_changed()
> will clear 'bridge_d3' of the upstream bridge.
>
> For all PCI ports where 'bridge_d3' is set we also enable and unblock
> runtime PM automatically. Only exception is when the PCIe port claims to
> support hotplug. More information about that is in the changelog of
> patch [4/4].
>
> Since this also touches xhci, I'm adding Mathias and Greg to check if the
> change looks reasonable.
>

For the non-functional one-line only xhci change in patch 2/4:
Acked-by: Mathias Nyman <mathias.nyman@linux.intel.com>

Out of curiosity, does enabling bridge d3 in any way impact #PME
wakeup signaling initiated by devices behind that bridge?

-Mathias