linux-kernel - Re: [RFC][RFT][PATCH] ACPI: Protection from suspending in the middle of EC transaction

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Date:	Mon, 01 Feb 2010 13:22:55 +0300
From:	Alexey Starikovskiy <astarikovskiy@...e.de>
To:	Henrique de Moraes Holschuh <hmh@....eng.br>
CC:	Maxim Levitsky <maximlevitsky@...il.com>,
	Alan Jenkins <sourcejedi.lkml@...glemail.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Len Brown <lenb@...nel.org>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	Thomas Renninger <trenn@...e.de>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][RFT][PATCH] ACPI: Protection from suspending in the middle
  of EC transaction

Henrique de Moraes Holschuh пишет:
> On Sun, 31 Jan 2010, Maxim Levitsky wrote:
>> Unfortunately, this patch even causes regressions on my notebook (it
>> survive 63 hibernate cycles), but now I battery driver reports 'battery
>> absent', backlight driver reports 0 brightness, but reload helped.
> 
> ...
> 
>> I think that not only _PTS ans _WAK are problematic. What about other
>> ACPI drivers that start accessing the EC before it is resumed?
>> I think that these cause the problems I observe.
> 
> ACPI drivers might access the EC (even indirectly, through the DSDT).  And
> platform drivers do often access the EC both at suspend and resume time.
Actually, only SBS and thinkpad-acpi access EC directly. All others go through
DSDT for access. Still, stopping EC in .suspend is too early, IMHO...
> 
> This needs some sort of strong ordering, the EC must suspend last, and
> resume first (as seen by any ACPI and ACPI-aware drivers such as libata,
> some platform drivers, etc).  If EC interrupts are a problem, maybe it can
> be kicked to poll mode for the suspend/resume transition?
It's this way already for about a year now... The problem is that EC driver might be 
stopped in middle of the transaction, thus leaving EC in unknown state for BIOS or 
switch-over kernel.

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