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 06:38:45 -0500
From:   Mario Limonciello <mario.limonciello@....com>
To:     Mika Westerberg <mika.westerberg@...ux.intel.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 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.

> - 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
> 
> ?

Thanks! That sounds very reasonable to me.  I'll double check it in my case.