Re: [PATCH] PCI / PM: Force devices to D0 in pci_pm_thaw_noirq()

[Bjorn Helgaas]

On Fri, Dec 15, 2017 at 03:07:18AM +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> 
> It is incorrect to call pci_restore_state() for devices in low-power
> states (D1-D3), as that involves the restoration of MSI setup which
> requires MMIO to be operational and that is only the case in D0.
> 
> However, pci_pm_thaw_noirq() may do that if the driver's "freeze"
> callbacks put the device into a low-power state, so fix it by making
> it force devices into D0 via pci_set_power_state() instead of trying
> to "update" their power state which is pointless.
> 
> Fixes: e60514bd4485 (PCI/PM: Restore the status of PCI devices across hibernation)
> Cc: 4.13+ <stable@xxxxxxxxxxxxxxx> # 4.13+
> Reported-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Reported-by: Maarten Lankhorst <dev@xxxxxxxxxxxxxx>
> Tested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Tested-by: Maarten Lankhorst <dev@xxxxxxxxxxxxxx>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>

Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>

Let me know if you want me to take this.  I don't have anything
currently queued up that touches pci-driver.c, so I'm happy if you
take it yourself.

> ---
> 
> The bug is not as old as I thought, actually.
> 
> Yes, we did the pci_update_current_state() in pci_pm_thaw_noirq()
> forever, but it started to be problematic in 4.13, when we started
> to call pci_restore_state() in addition to it to fix another issue.
> 
> ---
>  drivers/pci/pci-driver.c |    7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> Index: linux-pm/drivers/pci/pci-driver.c
> ===================================================================
> --- linux-pm.orig/drivers/pci/pci-driver.c
> +++ linux-pm/drivers/pci/pci-driver.c
> @@ -1027,7 +1027,12 @@ static int pci_pm_thaw_noirq(struct devi
>  	if (pci_has_legacy_pm_support(pci_dev))
>  		return pci_legacy_resume_early(dev);
>  
> -	pci_update_current_state(pci_dev, PCI_D0);
> +	/*
> +	 * pci_restore_state() requires the device to be in D0 (because of MSI
> +	 * restoration among other things), so force it into D0 in case the
> +	 * driver's "freeze" callbacks put it into a low-power state directly.
> +	 */
> +	pci_set_power_state(pci_dev, PCI_D0);
>  	pci_restore_state(pci_dev);
>  
>  	if (drv && drv->pm && drv->pm->thaw_noirq)
>