linux-kernel - Re: [PATCH 1/7] PCI/PM: Always return devices to D0 when thawing

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Date:   Tue, 15 Oct 2019 19:15:46 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Dexuan Cui <decui@...rosoft.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Michael Kelley <mikelley@...rosoft.com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>, olaf@...fle.de,
        apw@...onical.com, jasowang@...hat.com, vkuznets@...hat.com,
        marcelo.cerri@...onical.com, jackm@...lanox.com,
        linux-pci@...r.kernel.org, linux-hyperv@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        driverdev-devel@...uxdriverproject.org,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Linux PM <linux-pm@...r.kernel.org>
Subject: Re: [PATCH 1/7] PCI/PM: Always return devices to D0 when thawing

On Tuesday, October 15, 2019 1:00:10 AM CEST Bjorn Helgaas wrote:
> From: Dexuan Cui <decui@...rosoft.com>
> 
> pci_pm_thaw_noirq() is supposed to return the device to D0 and restore its
> configuration registers, but previously it only did that for devices whose
> drivers implemented the new power management ops.
> 
> Hibernation, e.g., via "echo disk > /sys/power/state", involves freezing
> devices, creating a hibernation image, thawing devices, writing the image,
> and powering off.  The fact that thawing did not return devices with legacy
> power management to D0 caused errors, e.g., in this path:
> 
>   pci_pm_thaw_noirq
>     if (pci_has_legacy_pm_support(pci_dev)) # true for Mellanox VF driver
>       return pci_legacy_resume_early(dev)   # ... legacy PM skips the rest
>     pci_set_power_state(pci_dev, PCI_D0)
>     pci_restore_state(pci_dev)
>   pci_pm_thaw
>     if (pci_has_legacy_pm_support(pci_dev))
>       pci_legacy_resume
> 	drv->resume
> 	  mlx4_resume
> 	    ...
> 	      pci_enable_msix_range
> 	        ...
> 		  if (dev->current_state != PCI_D0)  # <---
> 		    return -EINVAL;
> 
> which caused these warnings:
> 
>   mlx4_core a6d1:00:02.0: INTx is not supported in multi-function mode, aborting
>   PM: dpm_run_callback(): pci_pm_thaw+0x0/0xd7 returns -95
>   PM: Device a6d1:00:02.0 failed to thaw: error -95
> 
> Return devices to D0 and restore config registers for all devices, not just
> those whose drivers support new power management.
> 
> [bhelgaas: also call pci_restore_state() before pci_legacy_resume_early(),
> update comment, add stable tag, commit log]
> Link: https://lore.kernel.org/r/KU1P153MB016637CAEAD346F0AA8E3801BFAD0@KU1P153MB0166.APCP153.PROD.OUTLOOK.COM
> Signed-off-by: Dexuan Cui <decui@...rosoft.com>
> Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
> Cc: stable@...r.kernel.org	# v4.13+

No issues found, so

Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

> ---
>  drivers/pci/pci-driver.c | 17 +++++++++++------
>  1 file changed, 11 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
> index a8124e47bf6e..d4ac8ce8c1f9 100644
> --- a/drivers/pci/pci-driver.c
> +++ b/drivers/pci/pci-driver.c
> @@ -1076,17 +1076,22 @@ static int pci_pm_thaw_noirq(struct device *dev)
>  			return error;
>  	}
>  
> -	if (pci_has_legacy_pm_support(pci_dev))
> -		return pci_legacy_resume_early(dev);
> -
>  	/*
> -	 * 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.
> +	 * Both the legacy ->resume_early() and the new pm->thaw_noirq()
> +	 * callbacks assume the device has been returned to D0 and its
> +	 * config state has been restored.
> +	 *
> +	 * In addition, pci_restore_state() restores MSI-X state in MMIO
> +	 * space, which requires the device to be in D0, so return it to D0
> +	 * in case the driver's "freeze" callbacks put it into a low-power
> +	 * state.
>  	 */
>  	pci_set_power_state(pci_dev, PCI_D0);
>  	pci_restore_state(pci_dev);
>  
> +	if (pci_has_legacy_pm_support(pci_dev))
> +		return pci_legacy_resume_early(dev);
> +
>  	if (drv && drv->pm && drv->pm->thaw_noirq)
>  		error = drv->pm->thaw_noirq(dev);
>  
>