linux-kernel - Re: [PATCH] pci: fix kexec with power state D3

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Message-Id: <200903081108.24541.rjw@sisk.pl>
Date:	Sun, 8 Mar 2009 11:08:23 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Matthew Wilcox <matthew@....cx>,
	Jesse Brandeburg <jesse.brandeburg@...il.com>,
	David Miller <davem@...emloft.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	NetDev <netdev@...r.kernel.org>, linux-pci@...r.kernel.org,
	pm list <linux-pm@...ts.linux-foundation.org>
Subject: Re: [PATCH] pci: fix kexec with power state D3

On Sunday 08 March 2009, Yinghai Lu wrote:
> 
> Impact: second kernel by kexec will have some pci devices working
> 
> Found one system with 82575EB, in the kernel that is kexeced, probe igb
> failed with -2.
> 
> it looks like the same behavior happened on forcedeth.
> try to check system_state to make sure if put it on D3

This is not enough, because the PM code doesn't change system_state and
it uses pci_set_power_state too.

> Jesse Brandeburg said that we should do that check in core code instead of
> every device driver.

Well, I'm not really sure.  The drivers are where the bug is.

> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
> 
> ---
>  drivers/pci/pci.c |   17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> Index: linux-2.6/drivers/pci/pci.c
> ===================================================================
> --- linux-2.6.orig/drivers/pci/pci.c
> +++ linux-2.6/drivers/pci/pci.c
> @@ -593,6 +593,14 @@ int pci_set_power_state(struct pci_dev *
>  	if (state == PCI_D3hot && (dev->dev_flags & PCI_DEV_FLAGS_NO_D3))
>  		return 0;
>  
> +	/*
> +	 * Apparently it is not possible to reinitialise from D3 hot,
> +	 * only put the device into D3 if we really go for poweroff.
> +	 */
> +	if (system_state != SYSTEM_POWER_OFF &&
> +	    (state == PCI_D3hot || state == PCI_D3cold))
> +		return 0;
> +

This breaks suspend/hibernation, doesn't it?  Surely, we want to put devices
into D3 when going for suspend, for example.

That's apart from the fact that the 'state == PCI_D3cold' is redundant.

>  	error = pci_raw_set_power_state(dev, state, true);
>  
>  	if (state > PCI_D0 && platform_pci_power_manageable(dev)) {
> @@ -1124,6 +1132,15 @@ int pci_enable_wake(struct pci_dev *dev,
>  	int error = 0;
>  	bool pme_done = false;
>  
> +	/*
> +	 * Apparently it is not possible to reinitialise from D3 hot,
> +	 * only put the device into D3 if we really go for poweroff.
> +	 * we only need to enable wake when we are going to power off
> +	 */
> +	if (enable && system_state != SYSTEM_POWER_OFF &&
> +	    (state == PCI_D3hot || state == PCI_D3cold))
> +		return 0;
> +
>  	if (enable && !device_may_wakeup(&dev->dev))
>  		return -EINVAL;

I don't like this at all, sorry.

I thought we were supposed to avoid using system_state in such a way,
apart from the other things.

Thanks,
Rafael
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