Re: [RFC PATCH v2 1/3] PCI: rockchip: Add support for pcie wake irq

From: Brian Norris <briannorris@chromium.org>
To: Tony Lindgren <tony@atomide.com>
Cc: Heiko Stuebner <heiko@sntech.de>,
	linux-pci@vger.kernel.org, shawn.lin@rock-chips.com,
	jeffy <jeffy.chen@rock-chips.com>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	linux-kernel@vger.kernel.org, dianders@chromium.org,
	linux-rockchip@lists.infradead.org, bhelgaas@google.com,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH v2 1/3] PCI: rockchip: Add support for pcie wake irq
Date: Fri, 22 Dec 2017 15:20:44 -0800	[thread overview]
Message-ID: <20171222232043.GA158981@google.com> (raw)
In-Reply-To: <20171220191912.GM3875@atomide.com>

+ Rafael to this thread

On Wed, Dec 20, 2017 at 11:19:12AM -0800, Tony Lindgren wrote:
> * Brian Norris <briannorris@chromium.org> [171219 00:50]:
> > On Wed, Aug 23, 2017 at 09:32:39AM +0800, Jeffy Chen wrote:
> > 
> > Did this problem ever get resolved? To be clear, I believe the problem
> > at hand is:
> > 
> > (a) in suspend/resume (not runtime PM; we may not even have runtime PM
> > support for most PCI devices)
> 
> It seems it should be enough to implement runtime PM in the PCI
> controller. Isn't each PCI WAKE# line is wired from each PCI device
> to the PCI controller?

No, not really. As discussed in later versions of this thread already,
the WAKE# hierarchy is orthogonal to the PCI hierarchy, and I think we
settled that it's reasonable to just consider this as a 1-per-device
thing, with each device "directly" attached to the PM controller. While
sharing could happen, that's something we decided to punt on...didn't
we?

> Then the PCI controller can figure out from which PCI device the
> WAKE# came from.

I'm not completely sure of the details, but I believe this *can* be
determined by PME. But I'm not sure it's guaranteed to be supported,
especially in cases where we already have 1:1 WAKE#. So we should be
*trying* to report this wakeirq info from the device, if possible.

> > Options I can think of:
> > (1) implement runtime PM callbacks for all PCI devices, where we clear
> > any PME status and ensure WAKE# stops asserting [1]
> 
> I don't think this is needed, it should be enough to have just
> the PCI controller implement runtime PM :)

Brian

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