linux-kernel - Re: [PATCH] PCI: PM: Fix ordering of operations in pci_back_from

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Message-ID: <20211021010041.GA2655223@bhelgaas>
Date:   Wed, 20 Oct 2021 20:00:41 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linux PCI <linux-pci@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>
Subject: Re: [PATCH] PCI: PM: Fix ordering of operations in
 pci_back_from_sleep()

On Fri, Oct 15, 2021 at 06:45:59PM +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> The ordering of operations in pci_back_from_sleep() is incorrect,
> because the device may be in D3cold when it runs and pci_enable_wake()
> needs to access the device's configuration space which cannot be
> done in D3cold.
> 
> Fix this by calling pci_set_power_state() to put the device into D0
> before calling pci_enable_wake() for it.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

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

Thanks!

> ---
>  drivers/pci/pci.c |    7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> Index: linux-pm/drivers/pci/pci.c
> ===================================================================
> --- linux-pm.orig/drivers/pci/pci.c
> +++ linux-pm/drivers/pci/pci.c
> @@ -2638,8 +2638,13 @@ EXPORT_SYMBOL(pci_prepare_to_sleep);
>   */
>  int pci_back_from_sleep(struct pci_dev *dev)
>  {
> +	int ret = pci_set_power_state(dev, PCI_D0);
> +
> +	if (ret)
> +		return ret;
> +
>  	pci_enable_wake(dev, PCI_D0, false);
> -	return pci_set_power_state(dev, PCI_D0);
> +	return 0;
>  }
>  EXPORT_SYMBOL(pci_back_from_sleep);
>  
> 
> 
>