linux-kernel - Re: [PATCH v8 2/2] PCI/ACPI: Use device constraints instead of dates to opt devices into D3

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Message-ID: <20230803151454.GZ14638@black.fi.intel.com>
Date:   Thu, 3 Aug 2023 18:14:54 +0300
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Mario Limonciello <mario.limonciello@....com>
Cc:     "Rafael J . Wysocki" <rafael@...nel.org>,
        Bjorn Helgaas <helgaas@...nel.org>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
        Iain Lane <iain@...ngesquash.org.uk>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Subject: Re: [PATCH v8 2/2] PCI/ACPI: Use device constraints instead of dates
 to opt devices into D3

On Thu, Aug 03, 2023 at 06:38:45AM -0500, Mario Limonciello wrote:
> On 8/3/23 00:01, Mika Westerberg wrote:
> > Hi,
> > 
> > On Wed, Aug 02, 2023 at 03:10:13PM -0500, Mario Limonciello wrote:
> > > @@ -3036,11 +3044,8 @@ bool pci_bridge_d3_possible(struct pci_dev *bridge)
> > >   		if (dmi_check_system(bridge_d3_blacklist))
> > >   			return false;
> > > -		/*
> > > -		 * It should be safe to put PCIe ports from 2015 or newer
> > > -		 * to D3.
> > > -		 */
> > > -		if (dmi_get_bios_year() >= 2015)
> > > +		/* the platform indicates in a device constraint that D3 is needed */
> > > +		if (platform_constraint_d3(bridge))
> > 
> > This for sure causes some sort of power regression on the Intel
> > platforms made after 2015. Why not check for the constraint and:
> > 
> Are you sure?  I saw it as an explanation of how Windows could put the
> systems into D3 when there is no other PM related ACPI objects.

I'm concerned if there are no PEP constraints on some of the affected
systems this now leaves root ports into D0 then, no?