linux-kernel - Re: [PATCH 4.4 39/53] PCI/PM: Add needs_resume flag to avoid suspend complete optimization

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Date:   Tue, 06 Jun 2017 17:19:30 +0100
From:   Ben Hutchings <ben.hutchings@...ethink.co.uk>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Imre Deak <imre.deak@...el.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH 4.4 39/53] PCI/PM: Add needs_resume flag to avoid
 suspend complete optimization

On Mon, 2017-06-05 at 18:17 +0200, Greg Kroah-Hartman wrote:
> 4.4-stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Imre Deak <imre.deak@...el.com>
> 
> commit 4d071c3238987325b9e50e33051a40d1cce311cc upstream.
> 
> Some drivers - like i915 - may not support the system suspend direct
> complete optimization due to differences in their runtime and system
> suspend sequence.  Add a flag that when set resumes the device before
> calling the driver's system suspend handlers which effectively disables
> the optimization.
> 
> Needed by a future patch fixing suspend/resume on i915.

The patch for i915 isn't in this series, or even in mainline yet, so I
don't think this belongs in stable yet.  Also, based on the commit
message (commit adfdf85d795f "drm/i915: Prevent the system suspend
complete optimization") it appears that only 4.8 and later are affected
by the bug.

Ben.

> Suggested by Rafael.
> 
> Signed-off-by: Imre Deak <imre.deak@...el.com>
> Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> 
> ---
>  drivers/pci/pci.c   |    3 ++-
>  include/linux/pci.h |    5 +++++
>  2 files changed, 7 insertions(+), 1 deletion(-)
> 
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -2079,7 +2079,8 @@ bool pci_dev_keep_suspended(struct pci_d
>  
>  	if (!pm_runtime_suspended(dev)
>  	    || pci_target_state(pci_dev) != pci_dev->current_state
> -	    || platform_pci_need_resume(pci_dev))
> +	    || platform_pci_need_resume(pci_dev)
> +	    || (pci_dev->dev_flags & PCI_DEV_FLAGS_NEEDS_RESUME))
>  		return false;
>  
>  	/*
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -182,6 +182,11 @@ enum pci_dev_flags {
>  	PCI_DEV_FLAGS_NO_PM_RESET = (__force pci_dev_flags_t) (1 << 7),
>  	/* Get VPD from function 0 VPD */
>  	PCI_DEV_FLAGS_VPD_REF_F0 = (__force pci_dev_flags_t) (1 << 8),
> +	/*
> +	 * Resume before calling the driver's system suspend hooks, disabling
> +	 * the direct_complete optimization.
> +	 */
> +	PCI_DEV_FLAGS_NEEDS_RESUME = (__force pci_dev_flags_t) (1 << 11),
>  };
>  
>  enum pci_irq_reroute_variant {
> 
> 
> 

-- 
Ben Hutchings
Software Developer, Codethink Ltd.