linux-kernel - [095/111] ACPI: Fix regression where _PPC is not read at boot even when ignore

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Date:	Wed, 11 Aug 2010 16:55:16 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	"Darrick J. Wong" <djwong@...ibm.com>,
	Len Brown <len.brown@...el.com>, Jeff Mahoney <jeffm@...e.com>
Subject: [095/111] ACPI: Fix regression where _PPC is not read at boot even when ignore_ppc=0

2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Darrick J. Wong <djwong@...ibm.com>

commit 455c0d71d46e86b0b7ff2c9dcfc19bc162302ee9 upstream.

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@...ibm.com>
Signed-off-by: Len Brown <len.brown@...el.com>
Acked-by: Jeff Mahoney <jeffm@...e.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

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

--- a/drivers/acpi/processor_perflib.c
+++ b/drivers/acpi/processor_perflib.c
@@ -356,7 +356,11 @@ static int acpi_processor_get_performanc
 	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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