linux-kernel - Re: [PATCH v2] PCI: Don't assume root ports from

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Message-ID: <20230522114008.GK45886@black.fi.intel.com>
Date:   Mon, 22 May 2023 14:40:08 +0300
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Mario Limonciello <mario.limonciello@....com>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        S-k Shyam-sundar <Shyam-sundar.S-k@....com>,
        Natikar Basavaraj <Basavaraj.Natikar@....com>,
        Deucher Alexander <Alexander.Deucher@....com>,
        Iain Lane <iain@...ngesquash.org.uk>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH v2] PCI: Don't assume root ports from > 2015 are power
 manageable

On Mon, May 22, 2023 at 06:28:25AM -0500, Mario Limonciello wrote:
> On 5/22/23 00:55, Mika Westerberg wrote:
> > Hi Mario,
> > 
> > On Wed, May 17, 2023 at 10:08:27AM -0500, Mario Limonciello wrote:
> > > Using an XHCI device to wakeup the system from s2idle fails when
> > > that XHCI device is connected to a USB-C port for an AMD USB4
> > > router.
> > > 
> > > Due to commit 9d26d3a8f1b0 ("PCI: Put PCIe ports into D3 during
> > > suspend") all root port go into D3 during s2idle.
> > > When the root ports are in D3 over s2idle it's not possible for the
> > > platform firmware to properly identify the wakeup source.
> > > 
> > > Comparing registers between Linux and Windows 11 this behavior to put root
> > > ports into D3 at suspend is unique to Linux.  On an affected system
> > > Windows does not put the root ports into D3 over Modern Standby.
> > > 
> > > Windows doesn't put the root ports into D3 because root ports are not
> > > power manageable; they're missing _PRW and _S0W.
> > > 
> > > Linux shouldn't be assuming they support D3 just because they're newer
> > > than 2015, the ports should also be deemed power manageable.
> > > Add an extra check for this to ensure D3 isn't selected for such machines.
> > > 
> > > Fixes: 9d26d3a8f1b0 ("PCI: Put PCIe ports into D3 during suspend")
> > > Reported-by: Iain Lane <iain@...ngesquash.org.uk>
> > > Closes: https://forums.lenovo.com/t5/Ubuntu/Z13-can-t-resume-from-suspend-with-external-USB-keyboard/m-p/5217121
> > > Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> > > ---
> > >   drivers/pci/pci.c | 3 +++
> > >   1 file changed, 3 insertions(+)
> > > 
> > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> > > index 5ede93222bc1..3fe27aef09e6 100644
> > > --- a/drivers/pci/pci.c
> > > +++ b/drivers/pci/pci.c
> > > @@ -3010,6 +3010,9 @@ bool pci_bridge_d3_possible(struct pci_dev *bridge)
> > >   		if (dmi_check_system(bridge_d3_blacklist))
> > >   			return false;
> > > +		if (!platform_pci_power_manageable(bridge))
> > > +			return false;
> > > +
> > 
> > We already call platform_pci_bridge_d3() few lines up. That function
> > should know whether "platform" supports D3 for the bridges, and I think
> > it actually calls acpi_device_power_manageable() that platform_pci_power_manageable()
> > ends up checking too.
> 
> It does, but it doesn't end up returning false if it doesn't support it.  It
> only returns true if it does.

Good point!

> I've tested this patch on two different failing platforms and it works now
> on both.

Okay LGTM then,

Reviewed-by: Mika Westerberg <mika.westerberg@...ux.intel.com>