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

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Message-ID: <20090415225348.GW8311@plum>
Date:	Wed, 15 Apr 2009 15:53:49 -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] 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.

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

 drivers/acpi/processor_perflib.c |   19 ++++++++++++++-----
 1 files changed, 14 insertions(+), 5 deletions(-)


diff --git a/drivers/acpi/processor_perflib.c b/drivers/acpi/processor_perflib.c
index cafb410..0b50e8e 100644
--- a/drivers/acpi/processor_perflib.c
+++ b/drivers/acpi/processor_perflib.c
@@ -150,13 +150,10 @@ static int acpi_processor_get_platform_limit(struct acpi_processor *pr)
 	return 0;
 }
 
-int acpi_processor_ppc_has_changed(struct acpi_processor *pr)
+static int __acpi_processor_ppc_has_changed(struct acpi_processor *pr)
 {
 	int ret;
 
-	if (ignore_ppc)
-		return 0;
-
 	ret = acpi_processor_get_platform_limit(pr);
 
 	if (ret < 0)
@@ -165,6 +162,14 @@ int acpi_processor_ppc_has_changed(struct acpi_processor *pr)
 		return cpufreq_update_policy(pr->id);
 }
 
+int acpi_processor_ppc_has_changed(struct acpi_processor *pr)
+{
+	if (ignore_ppc)
+		return 0;
+
+	return __acpi_processor_ppc_has_changed(pr);
+}
+
 void acpi_processor_ppc_init(void)
 {
 	if (!cpufreq_register_notifier
@@ -348,7 +353,11 @@ 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_ppc_has_changed(pr);
+
+	return result;
 
 	/*
 	 * Having _PPC but missing frequencies (_PSS, _PCT) is a very good hint that
--
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