Acked-by: Len Brown <len.brown@xxxxxxxxx> On Tuesday 23 January 2007 11:16, Thomas Renninger wrote: > Can this one also be added to 2.6.19.X kernel. > Beside the Thinkpad it also seems to fix other system: > http://bugzilla.kernel.org/show_bug.cgi?id=7859 > > > Thanks, > > Thomas > > -------- Forwarded Message -------- > From: Len Brown <lenb@xxxxxxxxxx> > To: linux-acpi@xxxxxxxxxxxxxxx > Subject: Fwd: [patch] ACPI: fix cpufreq regression > Date: Tue, 16 Jan 2007 22:13:14 -0500 > > > nobody else with a T60 noticed this since November? > > I expect it's because the patch which caused the regression, > seemed to be rather safe and came in quite late... > > > > ---------- Forwarded Message ---------- > > Subject: [patch] ACPI: fix cpufreq regression > Date: Tuesday 16 January 2007 12:09 > From: Ingo Molnar <mingo@xxxxxxx> > To: Andrew Morton <akpm@xxxxxxxx> > Cc: linux-kernel@xxxxxxxxxxxxxxx, Dave Jones <davej@xxxxxxxxxx>, Linus Torvalds <torvalds@xxxxxxxx>, Len Brown <lenb@xxxxxxxxxx> > > Subject: [patch] ACPI: fix cpufreq regression > From: Ingo Molnar <mingo@xxxxxxx> > > recently cpufreq support on my laptop (Lenovo T60) broke completely: > when it's plugged into AC it would never go higher than 1 GHz - neither > 1.3 GHz nor 1.83 GHz is possible - no matter which governor (userspace, > speed or ondemand) is used. > > after some cpufreq debugging i tracked the regression back to the > following (totally correct) bug-fix commit: > > commit 0916bd3ebb7cefdd0f432e8491abe24f4b5a101e > Author: Dave Jones <davej@xxxxxxxxxx> > Date: Wed Nov 22 20:42:01 2006 -0500 > > [PATCH] Correct bound checking from the value returned from _PPC method. > > this bugfix, which makes other laptops work, made a previously hidden > (BIOS) bug visible on my laptop. > > The bug is the following: if the _PPC (Performance Present Capabilities) > optional ACPI object is queried /after/ bootup then the BIOS reports an > incorrect value of '2'. > > My laptop (Lenovo T60) has the following performance states supported: > > 0: 1833000 > 1: 1333000 > 2: 1000000 > > Per ACPI specification, a _PPC value of '0' means that all 3 performance > states are usable. A _PPC value of '1' means states 1 .. 2 are usable, a > value of '2' means only state '2' (slowest) is usable. > > now, the _PPC object is optional, and it also comes with notification. > Furthermore, when a CPU object is initialized, the _PPC object is > initialized as well. So the following evaluation of the _PPC object is > superfluous: > > [<c028ba5f>] acpi_processor_get_platform_limit+0xa1/0xaf > [<c028c040>] acpi_processor_register_performance+0x3b9/0x3ef > [<c0111a85>] acpi_cpufreq_cpu_init+0xb7/0x596 > [<c03dab74>] cpufreq_add_dev+0x160/0x4a8 > [<c02bed90>] sysdev_driver_register+0x5a/0xa0 > [<c03d9c4c>] cpufreq_register_driver+0xb4/0x176 > [<c068ac08>] acpi_cpufreq_init+0xe5/0xeb > [<c010056e>] init+0x14f/0x3dd > > and this is the point where my laptop's BIOS returns the incorrect value > of '2'. Note that it has not sent any notification event, so the value > is probably not really intentional (possibly spurious), and Windows > likely doesnt query it after bootup either. Maybe the value is kept at > '2' normally, and is only set to the real value when a true asynchronous > event (such as AC plug event, battery switch, etc.) occurs. > > So i /think/ this is a grey area of the ACPI spec: per the letter of the > spec the _PPC value only changes when notified, so there's no reason to > query it after the system has booted up. So in my opinion the best (and > most compatible) strategy would be to do the change below, and to not > evaluate the _PPC object in the acpi_processor_get_performance_info() > call, but only evaluate it if _PPC is present during CPU object init, or > if it's notified during an asynchronous event. This change is more > permissive than the previous logic, so it definitely shouldnt break any > existing system. > > This also happens to fix my laptop, which is merrily chugging along at > 1.83 GHz now. Yay! > > Signed-off-by: Ingo Molnar <mingo@xxxxxxx> > --- > drivers/acpi/processor_perflib.c | 4 ---- > 1 file changed, 4 deletions(-) > > Index: linux/drivers/acpi/processor_perflib.c > =================================================================== > --- linux.orig/drivers/acpi/processor_perflib.c > +++ linux/drivers/acpi/processor_perflib.c > @@ -322,10 +322,6 @@ static int acpi_processor_get_performanc > if (result) > return result; > > - result = acpi_processor_get_platform_limit(pr); > - if (result) > - return result; > - > return 0; > } > > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > > > ------------------------------------------------------- > - > To unsubscribe from this list: send the line "unsubscribe linux-acpi" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > - To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
