linux-kernel - Re: [PATCH 1/3] PCI / PM: Skip bridges in pci_enable

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Message-ID: <20170731205337.GF9303@bhelgaas-glaptop.roam.corp.google.com>
Date:   Mon, 31 Jul 2017 15:53:37 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linux PCI <linux-pci@...r.kernel.org>,
        Linux ACPI <linux-acpi@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH 1/3] PCI / PM: Skip bridges in pci_enable_wake()

On Fri, Jul 21, 2017 at 02:38:08PM +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> PCI bridges only have a reason to generate wakeup signals on behalf
> of devices below them, so avoid preparing bridges for wakeup directly
> in pci_enable_wake().
> 
> Also drop the pci_has_subordinate() check from pci_pm_default_resume()
> as this will be done by pci_enable_wake() itself now.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>

> ---
>  drivers/pci/pci-driver.c |    4 +---
>  drivers/pci/pci.c        |    7 +++++++
>  2 files changed, 8 insertions(+), 3 deletions(-)
> 
> Index: linux-pm/drivers/pci/pci.c
> ===================================================================
> --- linux-pm.orig/drivers/pci/pci.c
> +++ linux-pm/drivers/pci/pci.c
> @@ -1909,6 +1909,13 @@ int pci_enable_wake(struct pci_dev *dev,
>  {
>  	int ret = 0;
>  
> +	/*
> +	 * Bridges can only signal wakeup on behalf of subordinate devices,
> +	 * but that is set up elsewhere, so skip them.

A specific pointer to this "elsewhere" would be useful here.

> +	 */
> +	if (pci_has_subordinate(dev))
> +		return 0;
> +
>  	/* Don't do the same thing twice in a row for one device. */
>  	if (!!enable == !!dev->wakeup_prepared)
>  		return 0;
> Index: linux-pm/drivers/pci/pci-driver.c
> ===================================================================
> --- linux-pm.orig/drivers/pci/pci-driver.c
> +++ linux-pm/drivers/pci/pci-driver.c
> @@ -642,9 +642,7 @@ static int pci_legacy_resume(struct devi
>  static void pci_pm_default_resume(struct pci_dev *pci_dev)
>  {
>  	pci_fixup_device(pci_fixup_resume, pci_dev);
> -
> -	if (!pci_has_subordinate(pci_dev))
> -		pci_enable_wake(pci_dev, PCI_D0, false);
> +	pci_enable_wake(pci_dev, PCI_D0, false);
>  }
>  
>  static void pci_pm_default_suspend(struct pci_dev *pci_dev)
>