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

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Date:   Thu, 3 Aug 2023 08:01:18 +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

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:

- If present and enabled, use the desired D-state
- If present and disabled, leave the device in D0
- If not present use the existing cutoff date

?