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From: Konstantin Kharlamov <hi-angel@yandex.ru>
To: Bjorn Helgaas <helgaas@kernel.org>, Lukas Wunner <lukas@wunner.de>
Cc: linux-pci@vger.kernel.org,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Andreas Noever <andreas.noever@gmail.com>,
	linux-pm@vger.kernel.org
Subject: Re: [PATCH] PCI: don't power-off apple thunderbolt controller on s2idle
Date: Wed, 12 May 2021 23:36:47 +0300	[thread overview]
Message-ID: <949ea2de32241807b781f119fb14390e92845081.camel@yandex.ru> (raw)
In-Reply-To: <8ddea02fc6d37f7c444a1e90c9f03d7656ffe957.camel@yandex.ru>

Bjorn: so, given this and other comments, what's the decision on this patch? Any
particular changes I should do for it to be accepted?

On Fri, 2021-05-07 at 17:08 +0300, Konstantin Kharlamov wrote:
> On Fri, 2021-05-07 at 08:30 -0500, Bjorn Helgaas wrote:
> > On Fri, May 07, 2021 at 12:07:38AM +0200, Lukas Wunner wrote:
> > > On Thu, May 06, 2021 at 04:48:42PM -0500, Bjorn Helgaas wrote:
> > > > On Thu, May 06, 2021 at 08:38:20PM +0300, Konstantin Kharlamov wrote:
> > > > > On Macbook 2013 resuming from s2idle results in external monitor no
> > > > > longer being detected, and dmesg having errors like:
> > > > > 
> > > > >     pcieport 0000:06:00.0: can't change power state from D3hot to D0
> > > > > (config space inaccessible)
> > > > > 
> > > > > and a stacktrace. The reason turned out that the hw that the quirk
> > > > > powers off does not get powered on back on resume.
> > > > 
> > > > quirk_apple_poweroff_thunderbolt() was added in 2014 by 1df5172c5c25
> > > > ("PCI: Suspend/resume quirks for Apple thunderbolt").  It claims
> > > > "power is automatically restored before resume," so there must be
> > > > something special about s2idle that prevents the power-on.
> > > 
> > > With s2idle, the machine isn't suspended via ACPI, so the AML code
> > > which powers the controller off isn't executed.  The dance to prepare
> > > the controller for power-off consequently isn't necessary but rather
> > > harmful.
> > > 
> > > To get the same power savings as with ACPI suspend, the controller
> > > needs to be powered off via runtime suspend.  I posted patches for
> > > that back in 2016.  I'm using them on my laptop, they need some
> > > polishing and rebasing before I can repost them due to massive
> > > changes that have happened in the thunderbolt driver in the meantime.
> > > Without these patches, the controller sucks 1.5W of power in s2idle.
> > > 
> > > > Obviously the *hardware* hasn't changed since 1df5172c5c25.  Is s2idle
> > > > something that wasn't tested back then, or is this problem connected
> > > > to an s2idle change since then?  Can we identify a commit that
> > > > introduced this problem?  That would help with backporting or stable
> > > > tags.
> > > 
> > > Yes I believe the quirk predates the introduction of s2idle by a couple
> > > of years.
> > 
> > In an ideal world, we would know which commit introduced s2idle and
> > hence the possibility of hitting this bug, and we would add a Fixes:
> > tag for that commit so we could connect this fix with it.
> > 
> > Apart from that, what I don't like about this (and about the original
> > 1df5172c5c25) is that there's no connection to a spec or to documented
> > behavior of the device or of suspend/resume.
> 
> I did some research, and found that s2idle was first introduced in 2013 in
> commit 7e73c5ae6e799 (except it wasn't called "s2idle", by that name it goes
> since around 2016 as Lukas mentioned. In 7e73c5ae6e799 it is called "freeze").
> This is before 1df5172c5c25 which was added in 2014, so I guess we can add a:
> 
>         Fixes: 1df5172c5c25 ("PCI: Suspend/resume quirks for Apple
> thunderbolt")
> 
> > For example, "With s2idle, the machine isn't suspended via ACPI, so
> > the AML code which powers the controller off isn't executed."  AFAICT
> > that isn't actually a required, documented property of s2idle, but
> > rather it reaches into the internal implementation.
> > 
> > The code comment "If suspend mode is s2idle, power won't get restored
> > on resume" is similar.  !pm_suspend_via_firmware() tells us that
> > platform firmware won't be invoked.  But the connection between *that*
> > and "power won't get restored" is unexplained.
> 
> Sorry, I can't comment anything regarding AML and power management in general
> since I am really new to all of this. However, regarding the usage of the
> `pm_suspend_via_firmware()`: yeah, I also think it is unclear what this does,
> and I was thinking about adding a wrapper function something like
> `is_s2idle()` to the suspend.h, which would simply call
> `pm_suspend_via_firmware` internally. I didn't do that because I thought that
> usage of pm_suspend_via_firmware() for that task is just something people
> working with power management are supposed to know, but if someone else
> questions it too, I can make such wrapper, it's just a 3 lines-of-code change.
> 
> FWIW, originally I found out that pm_suspend_via_firmware() can be used for
> detecting s2idle by simply asking about it on linux-pm:
> https://marc.info/?l=linux-pm&m=162029296108775&w=2
> 



  reply	other threads:[~2021-05-12 21:10 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-06 17:38 [PATCH] PCI: don't power-off apple thunderbolt controller on s2idle Konstantin Kharlamov
2021-05-06 21:48 ` Bjorn Helgaas
2021-05-06 22:07   ` Lukas Wunner
2021-05-07  9:51     ` Rafael J. Wysocki
2021-05-08  8:48       ` Lukas Wunner
2021-05-07 13:30     ` Bjorn Helgaas
2021-05-07 14:08       ` Konstantin Kharlamov
2021-05-12 20:36         ` Konstantin Kharlamov [this message]
2021-05-17 19:51           ` PING " Konstantin Kharlamov
2021-05-19 17:28         ` Bjorn Helgaas
2021-05-19 19:12           ` Rafael J. Wysocki
2021-05-19 19:48             ` Bjorn Helgaas
2021-05-20 11:27               ` Rafael J. Wysocki
2021-05-20 11:54                 ` Rafael J. Wysocki
2021-05-20 19:49                   ` Bjorn Helgaas
2021-05-20 23:28                     ` Konstantin Kharlamov
2021-05-24  6:59                       ` Konstantin Kharlamov
2021-05-20 23:55                     ` [PATCH v2] PCI: don't call firmware hooks on suspend unless it's fw-controlled Konstantin Kharlamov
2021-05-28  7:39                       ` PING: " Konstantin Kharlamov
2021-06-03  8:36                         ` PING: " Konstantin Kharlamov
2021-06-03 17:46                           ` Bjorn Helgaas
2021-06-04  8:30                             ` Konstantin Kharlamov
2021-05-21  9:47                     ` [PATCH] PCI: don't power-off apple thunderbolt controller on s2idle Rafael J. Wysocki
2021-05-07 15:02       ` Rafael J. Wysocki
2021-05-08  8:20       ` Lukas Wunner
2021-05-07  9:32   ` Konstantin Kharlamov
2021-05-07 13:07     ` Bjorn Helgaas
2021-05-07 13:48       ` Konstantin Kharlamov
2021-05-20 11:58   ` Rafael J. Wysocki
2021-06-07 23:17 ` Bjorn Helgaas

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