Re: pcim_enable_device BUGs for libata devices in 2.6.20-git6

[Pavel Machek <pavel@ucw.cz>]

Hi!

> >I'm seeing BUGs like these on all libata-driven controllers when 
> >suspending to disk on 2.6.20-git6:
> >
> >sata_nv 0000:00:07.0: resuming
> >BUG: at drivers/pci/pci.c:817 pcim_enable_device()
> >
> >Call Trace:
> > [<ffffffff80337d21>] pcim_enable_device+0x8a/0xa5
> > [<ffffffff88099d18>] :libata:ata_pci_device_do_resume+0x20/0x59
> > [<ffffffff880bb731>] :sata_nv:nv_pci_device_resume+0x1d/0x100
> > [<ffffffff8039d2bf>] resume_device+0xcb/0x12c
> > [<ffffffff8039d3ac>] dpm_resume+0x8c/0xec
> > [<ffffffff8039d456>] device_resume+0x4a/0x5d
> > [<ffffffff802a0a33>] pm_suspend_disk+0x160/0x170
> > [<ffffffff8029f4b6>] enter_state+0x52/0x1da
> > [<ffffffff8029f69c>] state_store+0x5e/0x79
> > [<ffffffff802f2b20>] sysfs_write_file+0xe4/0x118
> > [<ffffffff80214b58>] vfs_write+0xce/0x177
> > [<ffffffff8021553e>] sys_write+0x45/0x6e
> > [<ffffffff8025711e>] system_call+0x7e/0x83
> >
> >It looks like what's happening is that during the "freezing" stage, we 
> >suspend and then resume the controllers. ata_pci_device_do_suspend only 
> >calls pci_disable_device if the event is PM_EVENT_SUSPEND but 
> >ata_pci_device_do_resume calls pcim_enable_device unconditionally. If 
> >the event was something else, then pcim_enable_device complains because 
> >the device was previously enabled and never disabled.
> >
> >Not sure what the best way to fix this is?
> 
> I think what should happen is either one of the followings.
> 
> 1. Don't restore power state and re-enable PCI device on resume from 
> freeze just as we don't do the opposite when freezing.
> 
> 2. Unconditionally disable and power down PCI device on suspend whether 
> it's freeze or not.
> 
> #2 would be simpler but I'm a bit worried about it.  There might be 
> controllers which choke after such sequence (save state, disable, power 
> down, no actual power removal, power on, restore state, re-enable).

I'd just go for #2.

> #1 can be easily done by taking a look at the current device power state 
> (gendev->power.power_state).  The problem is that no one in 
> suspend/resume path seems to be setting that variable except for
> runtime 

No, that variable is probably going to go away. If you want to
remember that you are resuming from freeze, just store that info in
private data structure.
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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