From: Tony Lindgren <tony-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org>
To: "Rafael J. Wysocki" <rafael-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: "Rafael J. Wysocki" <rjw-LthD3rsA81gm4RdzfppkhA@public.gmane.org>,
JeffyChen <jeffy.chen-TNX95d0MmH7DzftRWevZcw@public.gmane.org>,
Linux Kernel Mailing List
<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Bjorn Helgaas <bhelgaas-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
Linux PM <linux-pm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Shawn Lin <shawn.lin-TNX95d0MmH7DzftRWevZcw@public.gmane.org>,
Brian Norris
<briannorris-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>,
Doug Anderson <dianders-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>,
"devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Linux PCI <linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Rob Herring <robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
Frank Rowand
<frowand.list-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Subject: Re: [RFC PATCH v11 4/5] PCI / PM: Add support for the PCIe WAKE# signal for OF
Date: Thu, 28 Dec 2017 08:51:34 -0800 [thread overview]
Message-ID: <20171228165134.GH3875@atomide.com> (raw)
In-Reply-To: <CAJZ5v0hpK0_vjX3HinCpsFuKffVUn3d5EnqXdz0P893aRZgnRw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
* Rafael J. Wysocki <rafael-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> [171228 12:21]:
> On Thu, Dec 28, 2017 at 5:22 AM, Tony Lindgren <tony-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org> wrote:
> > * Rafael J. Wysocki <rafael-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> [171228 00:51]:
> >> On Wed, Dec 27, 2017 at 4:08 PM, Tony Lindgren <tony-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org> wrote:
> >> > * Rafael J. Wysocki <rjw-LthD3rsA81gm4RdzfppkhA@public.gmane.org> [171227 01:00]:
> >> >> On Tuesday, December 26, 2017 2:06:47 AM CET JeffyChen wrote:
> >> >> > Hi Rafael,
> >> >> >
> >> >> > Thanks for your reply :)
> >> >> >
> >> >> > On 12/26/2017 08:11 AM, Rafael J. Wysocki wrote:
> >> >> > >> >+
> >> >> > >> >+ dn = pci_device_to_OF_node(ppdev);
> >> >> > >> >+ if (!dn)
> >> >> > >> >+ return 0;
> >> >> > >> >+
> >> >> > >> >+ irq = of_irq_get_byname(dn, "wakeup");
> >> >> > > Why is this a property of the bridge and not of the device itself?
> >> >> >
> >> >> > That is suggested by Brian, because in that way, the wakeup pin would
> >> >> > not "tied to what exact device is installed (or no device, if it's a slot)."
> >> >>
> >> >> But I don't think it works when there are two devices using different WAKE#
> >> >> interrupt lines under the same bridge. Or how does it work then?
> >> >
> >> > It won't work currently for multiple devices but adding more than
> >> > one wakeriq per device is doable. And I think we will have other
> >> > cases where multiple wakeirqs are connected to a single device, so
> >> > that issue should be sorted out sooner or later.
> >> >
> >> > And if requesting wakeirq for the PCI WAKE# lines at the PCI
> >> > controller does the job, then maybe that's all we need to start with.
> >>
> >> These are expected to be out-of-band, so not having anything to do
> >> with the Root Complex.
> >>
> >> In-band PME Messages go through the PCIe hierarchy, but that is a
> >> standard mechanism and it is supported already.
> >>
> >> WAKE# are platform-specific, pretty much by definition and I guess
> >> that on most ARM boards they are just going to be some kind of GPIO
> >> pins.
> >
> > OK. So probably supporting the following two configurations
> > should be enough then:
> >
> > 1. One or more WAKE# lines configured as a wakeirq for the PCI
> > controller
> >
> > When the wakeirq calls pm_wakeup_event() for the PCI controller
> > device driver, the PCI controller wakes up and can deal with
> > it's child devices
>
> But this shouldn't be necessary at all. Or if it is, I wonder why
> that's the case.
Well Brian had a concern where we would have to implement PM runtime
for all device drivers for PCI devices.
> I'm assuming that we're talking about PCI Express here, which has two
> wakeup mechanisms defined, one of which is based on using PME Messages
> (Beacon) and the second one is WAKE#:
>
> "The WAKE# mechanism uses sideband signaling to implement wakeup
> functionality. WAKE# is
> an “open drain” signal asserted by components requesting wakeup and
> observed by the associated
> power controller."
>
> (from PCIe Base Spec 3.0). [And there's a diagram showing the routing
> of WAKE# in two cases in Figure 5-4: Conceptual Diagrams Showing Two
> Example Cases of WAKE# Routing.]
Thanks for the pointer, I had not seen that :) So the use cases
I was trying to describe above are similar to the wiring in the
PCIe Base Spec 3.0 "Figure 5-4" , but numbered the other way around.
> Note that WAKE# is defined to be "observed by the associated power
> controller", so I'm not sure what the PCI controller's role in the
> handing of it is at all.
To me it seems the "switch" part stays at least partially powered
and then in-band PME messages are used after host is woken up to
figure out which WAKE# triggered?
> > 2. Optionally a WAKE# line from a PCI device configured as wakeirq
> > for the PCI device driver
> >
> > In this case calling the PM runtime resume in the child
> > PCI device will also wake up the parent PCI controller,
> > and then the PCI controller can deal with it's children
> >
> > Seems like this series is pretty close to 1 above except
> > we need to have a list of wakeirqs per device instead of
> > just one. And option 2 should already work as long as the
> > PCI device driver parses and configures the wakeirq.
>
> Well, this is confusing, because as I said above, option 1 doesn't
> look relevant even.
So isn't my option 1 above similar to the PCIe spec "Figure 5-4"
case 2? Anyways, let's standardize on the "Figure 5-4" naming
from now to avoid confusion :)
> >> > Then in addition to that, we could do the following to allow
> >> > PCI devices to request the wakeirq from the PCI controller:
> >> >
> >> > 1. PCI controller or framework implements a chained irq for
> >> > the WAKE# lines assuming it can mask/unmask the WAKE# lines
> >> >
> >> > 2. PCI devices then can just request the wakeirq from the PCI
> >> > controller
> >> >
> >> > And that's about it. Optionally we could leave out the dependency
> >> > to having PCI devices implement PM runtime and just resume the
> >> > parent (PCI controller) if PCI devices has not implemented
> >> > PM runtime.
> >>
> >> So if my understanding is correct, DT should give you the WAKE# IRQ
> >> for the given endpoint PCI device and you only are expected to request
> >> it. The rest should just follow from the other pieces of information
> >> in the DT.
> >
> > Yeah and it seems that we should allow configuring both cases
> > 1 and 2 above.
> >
> >> With the quite obvious caveat that the same IRQ may be used as WAKE#
> >> for multiple endpoint devices (which BTW need not be under the same
> >> bridge even).
> >
> > And with the shared interrupts we can't do the masking/unmasking
> > automatically..
>
> Or we need to use reference counting (so actually the wakeup IRQs are
> not dedicated).
Yeah. FYI, for the dedicated wakeirq cases I have, we need to keep
them masked during runtime to avoid tons of interrupts as they
are often wired to the RX pins.
> >> >> > >> >+ if (irq == -EPROBE_DEFER)
> >> >> > > Braces here, please.
> >> >> > ok, will fix in the next version.
> >> >> >
> >> >> > >
> >> >> > >> >+ return irq;
> >> >> > >> >+ /* Ignore other errors, since a missing wakeup is non-fatal. */
> >> >> > >> >+ else if (irq < 0) {
> >> >> > >> >+ dev_info(&pdev->dev, "cannot get wakeup interrupt: %d\n", irq);
> >> >> > >> >+ return 0;
> >> >> > >> >+ }
> >> >> > >> >+
> >> >> > >> >+ device_init_wakeup(&pdev->dev, true);
> >> >> > > Why do you call this before dev_pm_set_dedicated_wake_irq()?
> >> >> >
> >> >> > hmmm, i thought so too, but it turns out the dedicated wake irq
> >> >> > framework requires device_init_wakeup(dev, true) before attach the wake irq:
> >> >> >
> >> >> > int device_wakeup_attach_irq(struct device *dev,
> >> >> > struct wake_irq *wakeirq)
> >> >> > {
> >> >> > struct wakeup_source *ws;
> >> >> >
> >> >> > ws = dev->power.wakeup;
> >> >> > if (!ws) {
> >> >> > dev_err(dev, "forgot to call device_init_wakeup?\n");
> >> >> > return -EINVAL;
> >> >> >
> >> >>
> >> >> Well, that's a framework issue, fair enough.
> >> >>
> >> >> That said, what if user space removes the wakeup source from under you
> >> >> concurrently via sysfs? Tony?
> >> >
> >> > Hmm sounds racy, need to take a look.
> >>
> >> Not only racy, as I don't see anything to prevent user space from
> >> making the dev->power.wakeup wakeup source go away via sysfs at any
> >> time *after* the IRQ has been requested.
> >
> > Currently nothing happens with wakeirqs if there's no struct
> > wakeup_source. On device_wakeup_enable() we call device_wakeup_attach()
> > that just copies dev->power.wakeirq to ws->wakeirq. And when struct
> > wake_source is freed the device should be active and wakeirq
> > disabled. Or are you seeing other issues here?
>
> I'm suspicious about one thing, but I need to look deeper into the code. :-)
OK. My response time will be laggy this week in case you find
something that needs urgent fixing :)
Regards,
Tony
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next prev parent reply other threads:[~2017-12-28 16:51 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-25 11:47 [RFC PATCH v11 0/5] PCI: rockchip: Move PCIe WAKE# handling into pci core Jeffy Chen
2017-12-25 11:47 ` [RFC PATCH v11 1/5] dt-bindings: PCI: Add definition of PCIe WAKE# irq and PCI irq Jeffy Chen
2017-12-25 11:47 ` [RFC PATCH v11 2/5] of/irq: Adjust of_pci_irq parsing for multiple interrupts Jeffy Chen
2017-12-25 11:47 ` [RFC PATCH v11 4/5] PCI / PM: Add support for the PCIe WAKE# signal for OF Jeffy Chen
[not found] ` <20171225114742.18920-5-jeffy.chen-TNX95d0MmH7DzftRWevZcw@public.gmane.org>
2017-12-26 0:11 ` Rafael J. Wysocki
2017-12-26 1:06 ` JeffyChen
2017-12-27 0:57 ` Rafael J. Wysocki
2017-12-27 15:08 ` Tony Lindgren
2017-12-28 0:48 ` Rafael J. Wysocki
[not found] ` <CAJZ5v0iaHPGiZJURhqZb8wdJXHxrAEHVN=U6rNHWGf-FGemPJA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-12-28 4:22 ` Tony Lindgren
[not found] ` <20171228042205.GG3875-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org>
2017-12-28 12:18 ` Rafael J. Wysocki
[not found] ` <CAJZ5v0hpK0_vjX3HinCpsFuKffVUn3d5EnqXdz0P893aRZgnRw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-12-28 16:51 ` Tony Lindgren [this message]
2017-12-28 17:29 ` Rafael J. Wysocki
2017-12-28 17:43 ` Rafael J. Wysocki
[not found] ` <CAJZ5v0hSMqwitCvfi7D+sknuO0YFr5F-kdkV-cSoVp30Cmdaeg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-12-29 17:16 ` Tony Lindgren
2017-12-29 17:15 ` Tony Lindgren
2017-12-29 23:39 ` Rafael J. Wysocki
[not found] ` <CAJZ5v0icePurJoGdVtX06j=XHPdZSqXgm+vhL47ngv7OZoL3fw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-12-30 0:21 ` Rafael J. Wysocki
2018-01-03 20:00 ` Tony Lindgren
[not found] ` <6120485.xubBpvge6h-yvgW3jdyMHm1GS7QM15AGw@public.gmane.org>
2018-01-03 20:08 ` Tony Lindgren
2018-01-05 0:11 ` Rafael J. Wysocki
2018-01-05 0:41 ` Brian Norris
[not found] ` <20180105004130.GA151625-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2018-01-05 1:13 ` Rafael J. Wysocki
2018-01-25 1:22 ` Brian Norris
2018-01-25 16:40 ` Tony Lindgren
2018-01-25 16:54 ` Rafael J. Wysocki
[not found] ` <CAJZ5v0h7JvEFTV1mbqxtK8P0aoums2Cvjy3uU1gK4E26_rtZ5g-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-01-25 17:47 ` Brian Norris
2017-12-25 11:47 ` [RFC PATCH v11 5/5] arm64: dts: rockchip: Move PCIe WAKE# irq to pcie port for Gru Jeffy Chen
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