linux-kernel - Re: [PATCH 1/2] vga_switcheroo: add power support for windows 10 machines.

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Message-ID: <20160315135743.GT1793@lahna.fi.intel.com>
Date:	Tue, 15 Mar 2016 15:57:43 +0200
From:	Mika Westerberg <mika.westerberg@...ux.intel.com>
To:	Lukas Wunner <lukas@...ner.de>
Cc:	Dave Airlie <airlied@...il.com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linux PCI <linux-pci@...r.kernel.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	dri-devel <dri-devel@...ts.freedesktop.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH 1/2] vga_switcheroo: add power support for windows 10
 machines.

On Tue, Mar 15, 2016 at 02:39:58PM +0100, Lukas Wunner wrote:
> Hi Mika,
> 
> On Mon, Mar 14, 2016 at 11:43:35AM +0200, Mika Westerberg wrote:
> > On Mon, Mar 14, 2016 at 12:19:14PM +1000, Dave Airlie wrote:
> > > On 11 March 2016 at 23:45, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> > > > On Friday, March 11, 2016 12:58:15 PM Mika Westerberg wrote:
> > > >> On Thu, Mar 10, 2016 at 09:57:09PM +0100, Rafael J. Wysocki wrote:
> > > >> > > It doesn't seem to do any runtime PM,
> > > >> > > I do wonder if pcieport should be doing it's own runtime PM handling,
> > > >> > > but that is a
> > > >> > > larger task than I'm thinking to tackle here.
> > > >> >
> > > >> > PCIe ports don't do PM - yet.  Mika has posted a series of patches to implement
> > > >> > that, however, that are waiting for comments now:
> > > >> >
> > > >> > https://patchwork.kernel.org/patch/8453311/
> > > >> > https://patchwork.kernel.org/patch/8453381/
> > > >> > https://patchwork.kernel.org/patch/8453391/
> > > >> > https://patchwork.kernel.org/patch/8453411/
> > > >> > https://patchwork.kernel.org/patch/8453371/
> > > >> > https://patchwork.kernel.org/patch/8453351/
> 
> If a pciehp port is runtime suspended and pciehp_poll_mode is enabled,
> the poll timer needs to be disabled and later reenabled on runtime resume.

If we disable the timer then we can't detect when a new device is
connected to the port.

I think in this case it might be better not to enable runtime PM for the
port at all.