Re: [PATCH v5 3/8] PCI: Don't block runtime PM for Thunderbolt host hotplug ports

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From	Mika Westerberg <mika.westerberg@linux.intel.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v5 3/8] PCI: Don't block runtime PM for Thunderbolt host hotplug ports
Date	Mon, 16 Jan 2017 11:40:02 +0100
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X-Original-Cc	Greg Kroah-Hartman <gregkh@linuxfoundation.org>, linux-kernel@vger.kernel.org, Andreas Noever <andreas.noever@gmail.com>, linux-pci@vger.kernel.org, linux-pm@vger.kernel.org, Bjorn Helgaas <helgaas@kernel.org>, "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
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On Sun, Jan 15, 2017 at 09:03:45PM +0100, Lukas Wunner wrote:
> Hotplug ports generally block their parents from suspending to D3hot as
> otherwise their interrupts couldn't be delivered.
> 
> An exception are Thunderbolt host controllers:  They have a separate
> GPIO pin to side-band signal plug events even if the controller is
> powered down or its parent ports are suspended to D3.  They can be told
> apart from Thunderbolt controllers in attached devices by checking if
> they're situated below a non-Thunderbolt device (typically a root port,
> or the downstream port of a PCIe switch in the case of the MacPro6,1).
> 
> To enable runtime PM for Thunderbolt on the Mac, the downstream bridges
> of a host controller must not block runtime PM on the upstream bridge as
> power to the chip is only cut once the upstream bridge has suspended.
> Amend the condition in pci_dev_check_d3cold() accordingly.
> 
> This change does not impact non-Macs as their Thunderbolt hotplug ports
> are handled by the firmware rather than natively by the OS:  The hotplug
> ports are not allowed to suspend in pci_bridge_d3_possible() and keep
> their parent ports awake all the time.  Consequently it is meaningless
> whether they block runtime PM on their parent ports or not.
> 
> Cc: Mika Westerberg <mika.westerberg@linux.intel.com>

Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>

Thread

[PATCH v5 3/8] PCI: Don't block runtime PM for Thunderbolt host  hotplug ports Lukas Wunner <lukas@wunner.de> - 2017-01-15 21:10 +0100
  Re: [PATCH v5 3/8] PCI: Don't block runtime PM for Thunderbolt host  hotplug ports Mika Westerberg <mika.westerberg@linux.intel.com> - 2017-01-16 11:40 +0100
  Re: [PATCH v5 3/8] PCI: Don't block runtime PM for Thunderbolt host  hotplug ports Bjorn Helgaas <helgaas@kernel.org> - 2017-01-29 00:10 +0100

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