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From: Bjorn Helgaas <>
To: "Rafael J. Wysocki" <>
Cc: Linux PCI <>,
	Stefan Gottwald <>,
	Mika Westerberg <>,
	Linux PM <>,
	LKML <>
Subject: Re: [PATCH] PCI: PM: Quirk bridge D3 on Elo i2
Date: Thu, 31 Mar 2022 16:57:16 -0500	[thread overview]
Message-ID: <20220331215716.GA27368@bhelgaas> (raw)
In-Reply-To: <11980172.O9o76ZdvQC@kreacher>

Hi Rafael,

On Thu, Mar 31, 2022 at 07:38:51PM +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <>
> If one of the PCIe root ports on Elo i2 is put into D3cold and then
> back into D0, the downstream device becomes permanently inaccessible,
> so add a bridge D3 DMI quirk for that system.
> This was exposed by commit 14858dcc3b35 ("PCI: Use
> pci_update_current_state() in pci_enable_device_flags()"), but before
> that commit the root port in question had never been put into D3cold
> for real due to a mismatch between its power state retrieved from the
> PCI_PM_CTRL register (which was accessible even though the platform
> firmware indicated that the port was in D3cold) and the state of an
> ACPI power resource involved in its power management.

In the bug report you suspect a firmware issue.  Any idea what that
might be?  It looks like a Gemini Lake Root Port, so I wouldn't think
it would be a hardware issue.

Weird how things come in clumps.  Was just looking at Mario's patch,
which also has to do with bridges and D3.

Do we need a Fixes line?  E.g.,

  Fixes: 14858dcc3b35 ("PCI: Use pci_update_current_state() in pci_enable_device_flags()")

> BugLink:
> Reported-by: Stefan Gottwald <>
> Signed-off-by: Rafael J. Wysocki <>
> ---
>  drivers/pci/pci.c |   10 ++++++++++
>  1 file changed, 10 insertions(+)
> Index: linux-pm/drivers/pci/pci.c
> ===================================================================
> --- linux-pm.orig/drivers/pci/pci.c
> +++ linux-pm/drivers/pci/pci.c
> @@ -2920,6 +2920,16 @@ static const struct dmi_system_id bridge
>  			DMI_MATCH(DMI_BOARD_VENDOR, "Gigabyte Technology Co., Ltd."),
>  		},
> +		/*
> +		 * Downstream device is not accessible after putting a root port
> +		 * into D3cold and back into D0 on Elo i2.
> +		 */
> +		.ident = "Elo i2",
> +		.matches = {
> +			DMI_MATCH(DMI_SYS_VENDOR, "Elo Touch Solutions"),
> +		},

Is this bridge_d3_blacklist[] similar to the PCI_DEV_FLAGS_NO_D3 bit?
Could they be folded together?  We have a lot of bits that seem
similar but maybe not exactly the same (dev->bridge_d3,
dev->no_d3cold, dev->d3cold_allowed, dev->runtime_d3cold,
PCI_DEV_FLAGS_NO_D3, pci_bridge_d3_force, etc.)  Ugh.

bridge_d3_blacklist[] itself was added by 85b0cae89d52 ("PCI:
Blacklist power management of Gigabyte X299 DESIGNARE EX PCIe ports"),
which honestly looks kind of random, i.e., it doesn't seem to be
working around a hardware or even a firmware defect.

Apparently the X299 issue is that 00:1c.4 is connected to a
Thunderbolt controller, and the BIOS keeps the Thunderbolt controller
powered off unless something is attached to it?  At least, 00:1c.4
leads to bus 05, and in the dmesg log attached to [1] shows no devices
on bus 05.

It also says the platform doesn't support PCIe native hotplug, which
matches what Mika said about it using ACPI hotplug.  If a system is
using ACPI hotplug, it seems like maybe *that* should prevent us from
putting things in D3cold?  How can we know whether ACPI hotplug
depends on a certain power state?



>  	},
>  #endif
>  	{ }

  reply	other threads:[~2022-03-31 21:57 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-03-31 17:38 [PATCH] PCI: PM: Quirk bridge D3 on Elo i2 Rafael J. Wysocki
2022-03-31 21:57 ` Bjorn Helgaas [this message]
2022-04-01 11:34   ` Rafael J. Wysocki
2022-04-04 14:46     ` Rafael J. Wysocki
2022-04-08 19:53       ` Bjorn Helgaas
2022-04-09 13:35         ` Rafael J. Wysocki
2022-04-10  9:16           ` Thorsten Leemhuis
2022-04-11 11:35             ` Rafael J. Wysocki
2022-04-11 12:10               ` Thorsten Leemhuis
2022-04-11 16:22                 ` Bjorn Helgaas
2022-05-26 22:12 ` Bjorn Helgaas
2022-05-27 18:55   ` Rafael J. Wysocki
2023-05-19  8:58 ` [PATCH] PCI: PM: Extend Elo i2 quirk to all systems using Continental Z2 board Ondrej Zary
2023-06-08 20:31   ` Bjorn Helgaas
2023-06-14  7:42     ` [PATCH] PCI/PM: " Ondrej Zary
2023-06-14 17:54       ` Bjorn Helgaas

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