Re: [PATCH v2] acpi: Fix regression where _PPC is not read at booteven when ignore_ppc=0

From: Darrick J. Wong
Date: Thu Feb 18 2010 - 13:28:47 EST


On Thu, Feb 18, 2010 at 04:02:39AM -0500, Len Brown wrote:
> > On Tue, Feb 16, 2010 at 10:07:07PM +0000, Matthew Garrett wrote:
> > > Did this ever get picked up?
> >
> > Nope. I vaguely recall asking a few times if there were any objections left,
> > but there weren't any, and I think Len or someone said it looked good back at
> > LPC last summer. Does not appear in 2.6.33-rc8 though.
>
> does it have a bugzilla entry? (as regressions tend to, thanks to rafael)
> I don't see this in my mailbox anymore.

Nope, no bugzilla entry. Do I need to create one now? A patch resend follows.

--D

---
Earlier, Ingo Molnar posted a patch to make it so that the kernel would avoid
reading _PPC on his broken T60. Unfortunately, it seems that with Thomas
Renninger's patch last July to eliminate _PPC evaluations when the processor
driver loads, the kernel never actually reads _PPC at all! This is problematic
if you happen to boot your non-T60 computer in a state where the BIOS _wants_
_PPC to be something other than zero.

So, put the _PPC evaluation back into acpi_processor_get_performance_info if
ignore_ppc isn't 1.

Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
---

drivers/acpi/processor_perflib.c | 6 +++++-
1 files changed, 5 insertions(+), 1 deletions(-)


diff --git a/drivers/acpi/processor_perflib.c b/drivers/acpi/processor_perflib.c
index 2cabadc..a959f6a 100644
--- a/drivers/acpi/processor_perflib.c
+++ b/drivers/acpi/processor_perflib.c
@@ -413,7 +413,11 @@ static int acpi_processor_get_performance_info(struct acpi_processor *pr)
if (result)
goto update_bios;

- return 0;
+ /* We need to call _PPC once when cpufreq starts */
+ if (ignore_ppc != 1)
+ result = acpi_processor_get_platform_limit(pr);
+
+ return result;

/*
* Having _PPC but missing frequencies (_PSS, _PCT) is a very good hint that
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