linux-kernel - [PATCH 3/3] CPUFREQ: processor.ko: Try to detect old BIOS, not supporting CPU freq on a recent CPU.

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Date:	Wed, 27 Aug 2008 15:27:11 +0200
From:	Thomas Renninger <trenn@...e.de>
To:	ak@...ux.intel.com
Cc:	bjorn.helgaas@...com, linux-kernel@...r.kernel.org,
	arjan@...ux.intel.com, linux-acpi@...r.kernel.org,
	ckornacker@...e.de, Thomas Renninger <trenn@...e.de>
Subject: [PATCH 3/3] CPUFREQ: processor.ko: Try to detect old BIOS, not supporting CPU freq on a recent CPU.

On Intel CPUs it is rather common and a good hint that BIOSes which do provide
_PPC func, but not the frequencies itself in _PSS function, are old and need
to be updated for CPU freq support.
Tell the user he has a BIOS/firmware problem.

Signed-off-by: Thomas Renninger <trenn@...e.de>
---
 drivers/acpi/processor_perflib.c |   18 +++++++++++++++---
 1 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/drivers/acpi/processor_perflib.c b/drivers/acpi/processor_perflib.c
index 0133af4..3a2886f 100644
--- a/drivers/acpi/processor_perflib.c
+++ b/drivers/acpi/processor_perflib.c
@@ -38,6 +38,7 @@
 
 #include <asm/uaccess.h>
 #endif
+#include <asm/cpufeature.h>
 
 #include <acpi/acpi_bus.h>
 #include <acpi/processor.h>
@@ -334,7 +335,6 @@ static int acpi_processor_get_performance_info(struct acpi_processor *pr)
 	acpi_status status = AE_OK;
 	acpi_handle handle = NULL;
 
-
 	if (!pr || !pr->performance || !pr->handle)
 		return -EINVAL;
 
@@ -347,13 +347,25 @@ static int acpi_processor_get_performance_info(struct acpi_processor *pr)
 
 	result = acpi_processor_get_performance_control(pr);
 	if (result)
-		return result;
+		goto update_bios;
 
 	result = acpi_processor_get_performance_states(pr);
 	if (result)
-		return result;
+		goto update_bios;
 
 	return 0;
+
+	/*
+	 * Having _PPC but missing frequencies (_PSS, _PCT) is a very good hint that
+	 * the BIOS is older than the CPU and does not know its frequencies
+	 */
+ update_bios:
+	if (ACPI_SUCCESS(acpi_get_handle(pr->handle, "_PPC", &handle))){
+		if(boot_cpu_has(X86_FEATURE_EST))
+			printk(KERN_WARNING FW_BUG "BIOS needs update for CPU "
+			       "frequency support\n");
+	}
+	return result;
 }
 
 int acpi_processor_notify_smm(struct module *calling_module)
-- 
1.5.4.5

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