[patch 35/50] CPUFREQ: Make acpi-cpufreq more robust against BIOS freq changes behind our back.

[Chris Wright]

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

From: Venkatesh Pallipadi <venkatesh.pallipadi@xxxxxxxxx>

upstream commit: e56a727b023d40d1adf660168883f30f2e6abe0a

We checked the hardware freq with OS cached freq value in get_cur_freqon_cpu().

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@xxxxxxxxx>
Signed-off-by: Thomas Renninger <trenn@xxxxxxx>
Signed-off-by: Dave Jones <davej@xxxxxxxxxx>
Cc: Thomas Renninger <trenn@xxxxxxx>
Cc: "Anthony L. Awtrey" <tony@xxxxxxxxxx>
[chrisw: backport to 2.6.25.4]
Signed-off-by: Chris Wright <chrisw@xxxxxxxxxxxx>
---
 arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

--- a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
+++ b/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
@@ -339,6 +339,7 @@ static unsigned int get_cur_freq_on_cpu(
 {
 	struct acpi_cpufreq_data *data = per_cpu(drv_data, cpu);
 	unsigned int freq;
+	unsigned int cached_freq;
 
 	dprintk("get_cur_freq_on_cpu (%d)\n", cpu);
 
@@ -347,7 +348,16 @@ static unsigned int get_cur_freq_on_cpu(
 		return 0;
 	}
 
+	cached_freq = data->freq_table[data->acpi_data->state].frequency;
 	freq = extract_freq(get_cur_val(cpumask_of_cpu(cpu)), data);
+	if (freq != cached_freq) {
+		/*
+		 * The dreaded BIOS frequency change behind our back.
+		 * Force set the frequency on next target call.
+		 */
+		data->resume = 1;
+	}
+
 	dprintk("cur freq = %u\n", freq);
 
 	return freq;

-- 
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