linux-kernel - Re: Time to re-enable Runtime PM per default for PCI devcies?

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Date:   Thu, 31 Dec 2020 05:07:35 +0100
From:   Lukas Wunner <lukas@...ner.de>
To:     Heiner Kallweit <hkallweit1@...il.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Bjorn Helgaas <helgaas@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Kai Heng Feng <kai.heng.feng@...onical.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Time to re-enable Runtime PM per default for PCI devcies?

On Wed, Dec 30, 2020 at 11:56:04PM +0100, Heiner Kallweit wrote:
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -3024,7 +3024,9 @@ void pci_pm_init(struct pci_dev *dev)
>  	u16 status;
>  	u16 pmc;
>  
> -	pm_runtime_forbid(&dev->dev);
> +	if (pci_acpi_forbid_runtime_pm())
> +		pm_runtime_forbid(&dev->dev);
> +

Generic PCI code usually does not call ACPI-specific functions directly,
but rather through a pci_platform_pm_ops callback.

FWIW, if platform_pci_power_manageable() returns true, it can probably
be assumed that allowing runtime PM by default is okay.  So as a first
step, you may want to call that instead of adding a new callback.

Thanks,

Lukas