[CPUFREQ] Make acpi-cpufreq more robust against BIOS freq changes behind our back.

We checked the hardware freq with OS cached freq value in get_cur_freqon_cpu().
Signed-off-by: NVenkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: NThomas Renninger <trenn@suse.de>
Signed-off-by: NDave Jones <davej@redhat.com>

arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c

@@ -339,6 +339,7 @@ static unsigned int get_cur_freq_on_cpu(unsigned int 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(unsigned int 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;