linux-kernel - Re: [PATCH] ACPI PM: Restore the 2.6.24 suspend ordering

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Date:	Sun, 30 Mar 2008 14:28:38 +0200
From:	Pavel Machek <pavel@...e.cz>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Len Brown <lenb@...nel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Carlos Corbacho <carlos@...angeworlds.co.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	Shaohua Li <shaohua.li@...el.com>,
	Felix Möller <fm@...nsuse.org>,
	Arthur Erhardt <erhardt@....physik.uni-tuebingen.de>,
	Matthew Garrett <mjg59@...f.ucam.org>
Subject: Re: [PATCH] ACPI PM: Restore the 2.6.24 suspend ordering

Hi!

> > > From: Rafael J. Wysocki <rjw@...k.pl>
> > > 
> > > Some time ago it turned out that our suspend code ordering broke
> > > some NVidia-based systems that hung if _PTS was executed with one of
> > > the PCI devices, specifically a USB controller, in a low power state.
> > > Then, it was noticed that the suspend code ordering was not compliant
> > > with ACPI 1.0, although it was compliant with ACPI 2.0 (and later),
> > > and it was argued that the code had to be changed for that reason
> > > (ref. http://bugzilla.kernel.org/show_bug.cgi?id=9528).  So we did,
> > > but evidently we did wrong, because it's now turning out that some
> > > systems have been broken by this change (refs.
> > > http://bugzilla.kernel.org/show_bug.cgi?id=10340 ,
> > > https://bugzilla.novell.com/show_bug.cgi?id=374217#c16).  [I said
> > > at that time that something like this might happend, but the majority
> > > of people involved thought that it was improbable due to the
> > > necessity to preserve the compliance of hardware with ACPI 1.0.]
> > > This actually is a quite serious regression from 2.6.24.
> > > 
> > > Moreover, the ACPI 1.0 ordering of suspend code introduced another
> > > issue that I have only noticed recently.  Namely, if the suspend of
> > > one of devices fails, the already suspended devices will be resumed
> > > without executing _WAK before, which leads to problems on some
> > > systems (for example, in such situations thermal management is
> > > broken on my HP nx6325).  Consequently, it also breaks suspend
> > > debugging on the affected systems.
> > > 
> > > Note also, that the requirement to execute _PTS before suspending
> > > devices does not really make sense, because the device in question
> > > may be put into a low power state at run time for a reason unrelated
> > > to a system-wide suspend.

Yes, but if we are putting them into lowpower state ourselves, we
should probably be doing that "by hand", without calling acpi
methods. _PTS may prepare something for acpi methods (which tell us
which PCI Dx state to put the device in at the very least).

> > > For the reasons outlined above, the change of the suspend ordering
> > > should be reverted, which is done by the patch below.
> > 
> > But this will break those few nvidia-based systems, no?
> > 
> > this may have been a good idea in -rc1 days, but we are in -rc7
> > now... and the patch is slightly big.
> 
> It's quite obvious, though.

Yes, but breaking systems between -rc7 and final is _very_ unnice.

> > What about something like: (hand-edited patch, sorry)
> 
> Well, I think that would be confusing.
> 
> The NVidia systems are broken anyway on 2.6.24.x, so we just don't fix them
> rather than break them and there are more reasons to do what the patch does
> (as pointed out in the changelog).  For example, your suggested patch doesn't
>  fix the error paths/debugging breakage described in the changelog.

But that should not be impossible to fix, right?

> I think we _can_ do something about the failing NVidia systems in the 2.6.26
> time frame, but that will require some more consideration.

We could simply blacklist them, no?
								Pavel

> >  Index: linux-2.6/drivers/acpi/sleep/main.c
> >  ===================================================================
> >  --- linux-2.6.orig/drivers/acpi/sleep/main.c
> >  +++ linux-2.6/drivers/acpi/sleep/main.c
> >  @@ -26,21 +26,6 @@ u8 sleep_states[ACPI_S_STATE_COUNT];
> >   
> >   #ifdef CONFIG_PM_SLEEP
> >   static u32 acpi_target_sleep_state = ACPI_STATE_S0;
> >  static bool acpi_sleep_finish_wake_up;
> >  
> > - /*
> > -  * ACPI 2.0 and later want us to execute _PTS after suspending devices, so we
> > -  * allow the user to request that behavior by using the 'acpi_new_pts_ordering'
> > -  * kernel command line option that causes the following variable to be set.
> > -  */
> >  static bool new_pts_ordering = true;
> >  
> >  -static int __init acpi_new_pts_ordering(char *str)
> >  +static int __init acpi_old_pts_ordering(char *str)
> >  {
> >  	new_pts_ordering = false;
> >  	return 1;
> >  }
> >  -__setup("acpi_old_pts_ordering", acpi_old_pts_ordering);
> >  +__setup("acpi_new_pts_ordering", acpi_new_pts_ordering);
> >   #endif
> >  
> >   static int acpi_sleep_prepare(u32 acpi_state)
> >  Index: linux-2.6/Documentation/kernel-parameters.txt
> >  ===================================================================
> >  --- linux-2.6.orig/Documentation/kernel-parameters.txt
> >  +++ linux-2.6/Documentation/kernel-parameters.txt
> >  @@ -170,11 +170,6 @@ and is between 256 and 4096 characters. 
> >   	acpi_irq_isa=	[HW,ACPI] If irq_balance, mark listed IRQs used by ISA
> >   			Format: <irq>,<irq>...
> >   
> >  -	acpi_new_pts_ordering [HW,ACPI]
> >  +	acpi_old_pts_ordering [HW,ACPI]
> >  -			Enforce the ACPI 2.0 ordering of the _PTS control
> >  +			Enforce the ACPI 1.0 ordering of the _PTS control
> >  			method wrt putting devices into low power states
> >  -			default: pre ACPI 2.0 ordering of _PTS
> >  +			default: ACPI 2.0 ordering of _PTS
> >  
> >   	acpi_no_auto_ssdt	[HW,ACPI] Disable automatic loading of SSDT
> >   
> >   	acpi_os_name=	[HW,ACPI] Tell ACPI BIOS the name of the OS
> > 
> 
> Thanks,
> Rafael
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