[PATCH v2 2/2] cpufreq: acpi-cpufreq: fix P-state index mismatch in get_cur_freq_on_cpu()

[lirongqing <lirongqing@baidu.com>]

From: Li RongQing <lirongqing@baidu.com>

get_cur_freq_on_cpu() reads the cached frequency as
policy->freq_table[to_perf_data(data)->state], mixing two different index
spaces: perf->state indexes perf->states[], while policy->freq_table[] is
built with duplicate frequencies removed and stores the original P-state
index in freq_table[].driver_data.

Once any _PSS entry has been skipped the two arrays no longer line up, so
the cached frequency used to detect a "BIOS changed frequency behind our
back" event could be taken from the wrong table slot.

Look up the freq_table entry whose driver_data matches perf->state instead
of indexing freq_table[] with perf->state directly.

Fixes: 8cee1eed8e78 ("cpufreq: ACPI: Remove freq_table from acpi_cpufreq_data")
Reported-by: Zhongqiu Han <zhongqiu.han@oss.qualcomm.com>
Signed-off-by: Li RongQing <lirongqing@baidu.com>
---
 drivers/cpufreq/acpi-cpufreq.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
index 1abe9ab..61ede49c 100644
--- a/drivers/cpufreq/acpi-cpufreq.c
+++ b/drivers/cpufreq/acpi-cpufreq.c
@@ -353,6 +353,7 @@ static u32 get_cur_val(const struct cpumask *mask, struct acpi_cpufreq_data *dat
 
 static unsigned int get_cur_freq_on_cpu(unsigned int cpu)
 {
+	struct cpufreq_frequency_table *pos;
 	struct acpi_cpufreq_data *data;
 	struct cpufreq_policy *policy;
 	unsigned int freq;
@@ -368,7 +369,13 @@ static unsigned int get_cur_freq_on_cpu(unsigned int cpu)
 	if (unlikely(!data || !policy->freq_table))
 		return 0;
 
-	cached_freq = policy->freq_table[to_perf_data(data)->state].frequency;
+	cached_freq = 0;
+	cpufreq_for_each_entry(pos, policy->freq_table)
+		if (pos->driver_data == to_perf_data(data)->state) {
+			cached_freq = pos->frequency;
+			break;
+		}
+
 	freq = extract_freq(policy, get_cur_val(cpumask_of(cpu), data));
 	if (freq != cached_freq) {
 		/*
-- 
2.9.4