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Subject[Patch 1/2] cpufreq: tegra194: get consistent cpuinfo_cur_freq
Date
Frequency returned by 'cpuinfo_cur_freq' using counters is not fixed
and keeps changing slightly. This change returns a consistent value
from freq_table. If the reconstructed frequency has acceptable delta
from the last written value, then return the frequency corresponding
to the last written ndiv value from freq_table. Otherwise, print a
warning and return the reconstructed freq.

Signed-off-by: Sumit Gupta <sumitg@nvidia.com>
---
drivers/cpufreq/tegra194-cpufreq.c | 66 ++++++++++++++++++++++++++++++++------
1 file changed, 57 insertions(+), 9 deletions(-)

diff --git a/drivers/cpufreq/tegra194-cpufreq.c b/drivers/cpufreq/tegra194-cpufreq.c
index e1d931c..d5b608d 100644
--- a/drivers/cpufreq/tegra194-cpufreq.c
+++ b/drivers/cpufreq/tegra194-cpufreq.c
@@ -180,9 +180,65 @@ static unsigned int tegra194_get_speed_common(u32 cpu, u32 delay)
return (rate_mhz * KHZ); /* in KHz */
}

+static void get_cpu_ndiv(void *ndiv)
+{
+ u64 ndiv_val;
+
+ asm volatile("mrs %0, s3_0_c15_c0_4" : "=r" (ndiv_val) : );
+
+ *(u64 *)ndiv = ndiv_val;
+}
+
+static void set_cpu_ndiv(void *data)
+{
+ struct cpufreq_frequency_table *tbl = data;
+ u64 ndiv_val = (u64)tbl->driver_data;
+
+ asm volatile("msr s3_0_c15_c0_4, %0" : : "r" (ndiv_val));
+}
+
static unsigned int tegra194_get_speed(u32 cpu)
{
- return tegra194_get_speed_common(cpu, US_DELAY);
+ struct cpufreq_frequency_table *table, *pos;
+ struct cpufreq_policy policy;
+ unsigned int rate;
+ u64 ndiv;
+ int err;
+
+ cpufreq_get_policy(&policy, cpu);
+ table = policy.freq_table;
+
+ /* reconstruct actual cpu freq using counters*/
+ rate = tegra194_get_speed_common(cpu, US_DELAY);
+
+ /* get last written ndiv value*/
+ err = smp_call_function_single(cpu, get_cpu_ndiv, &ndiv, true);
+ if (err) {
+ pr_err("cpufreq: Failed to get ndiv for CPU%d, ret:%d\n",
+ cpu, err);
+ return rate;
+ }
+
+ /* if the reconstructed frequency has acceptable delta from
+ * the last written value, then return freq corresponding
+ * to the last written ndiv value from freq_table. This is
+ * done to return consistent value.
+ */
+ cpufreq_for_each_valid_entry(pos, table) {
+ if (pos->driver_data != ndiv)
+ continue;
+
+ if (abs(pos->frequency - rate) > 115200) {
+ pr_warn("cpufreq: high delta (%d) on CPU%d\n",
+ abs(pos->frequency - rate), cpu);
+ pr_warn("cpufreq: cur:%u, set:%u, set ndiv:%llu\n",
+ rate, pos->frequency, ndiv);
+ } else {
+ rate = pos->frequency;
+ }
+ break;
+ }
+ return rate;
}

static int tegra194_cpufreq_init(struct cpufreq_policy *policy)
@@ -209,14 +265,6 @@ static int tegra194_cpufreq_init(struct cpufreq_policy *policy)
return 0;
}

-static void set_cpu_ndiv(void *data)
-{
- struct cpufreq_frequency_table *tbl = data;
- u64 ndiv_val = (u64)tbl->driver_data;
-
- asm volatile("msr s3_0_c15_c0_4, %0" : : "r" (ndiv_val));
-}
-
static int tegra194_cpufreq_set_target(struct cpufreq_policy *policy,
unsigned int index)
{
--
2.7.4
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