linux-kernel - [PATCH v2] acpi: Fix regression where _PPC is not read at boot even when ignore

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Date:	Wed, 15 Apr 2009 17:27:12 -0700
From:	"Darrick J. Wong" <djwong@...ibm.com>
To:	linux-kernel <linux-kernel@...r.kernel.org>
Cc:	Ingo Molnar <mingo@...e.hu>, Thomas Renninger <trenn@...e.de>,
	cpufreq@...r.kernel.org, linux-acpi@...r.kernel.org
Subject: [PATCH v2] acpi: Fix regression where _PPC is not read at boot
	even when ignore_ppc=0

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.

This second version restores the correct function call, which simplifies
the patch.  I apologize for the churn and the poor eyesight.

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

 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 cafb410..85af717 100644
--- a/drivers/acpi/processor_perflib.c
+++ b/drivers/acpi/processor_perflib.c
@@ -348,7 +348,11 @@ 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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