Re: [PATCH v2 1/2] cpufreq: tegra194: get consistent cpuinfo_cur_freq
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
---
drivers/cpufreq/tegra194-cpufreq.c | 71 +-
1 file changed, 62 insertions(+), 9 deletions(-)
diff --git a/drivers/cpufreq/tegra194-cpufreq.c
b/drivers/cpufreq/tegra194-cpufreq.c
index e1d931c..d250e49 100644
--- a/drivers/cpufreq/tegra194-cpufreq.c
+++ b/drivers/cpufreq/tegra194-cpufreq.c
@@ -180,9 +180,70 @@ 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)
You weren't required to do this unnecessary change.
ya, moved the function up to keep both {get_|set_} calls together.
+{
+ 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 tegra194_cpufreq_data *data = cpufreq_get_driver_data();
+ struct cpufreq_frequency_table *pos;
+ unsigned int rate;
+ u64 ndiv;
+ int ret;
+ u32 cl;
+
+ if (!cpu_online(cpu))
This isn't required. The CPU is guaranteed to be online here.
OK, will remove this in next version.
+ return -EINVAL;
+
+ smp_call_function_single(cpu, get_cpu_cluster, , true);
+
+ if (cl >= data->num_clusters)
Is it really possible here ? I meant you must have already checked
this at cpufreq-init level already. Else mark it unlikely at least.
Ya, will remove the check here.
+ return -EINVAL;
+
+ /* reconstruct actual cpu freq using counters */
+ rate = tegra194_get_speed_common(cpu, US_DELAY);
+
+ /* get last written ndiv value */
+ ret = smp_call_function_single(cpu, get_cpu_ndiv, , true);
+ if (ret) {
What exactly can fail here ? get_cpu_ndiv() can't fail. Do we really
need this check ? What about WARN_ON_ONCE() ?
OK.
+ pr_err("cpufreq: Failed to get ndiv for CPU%d, ret:%d\n",
+cpu, ret);
+ 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, data->tables[cl]) {
+ if (pos->driver_data != ndiv)
+ continue;
+
+ if (abs(pos->frequency - rate) > 115200) {
where does this 115200 comes from ? Strange that it matches tty's baud
rate :)
The value is equal to one freq step size.
This is 115 MHz, right ? Isn't that too big of a delta ?
The is the acceptable delta used during our testing keeping some margin.
+ pr_warn("cpufreq: cpu%d,cur:%u,set:%u,set ndiv:%llu\n",
+ cpu, rate, pos->frequency, ndiv);
+ } else {
+ rate = pos->frequency;
+ }
+ break;
+ }
+ return rate;
}
--
viresh
Re: [PATCH v2 1/2] cpufreq: tegra194: get consistent cpuinfo_cur_freq
On 08-10-20, 18:31, Sumit Gupta wrote:
> 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
> ---
> drivers/cpufreq/tegra194-cpufreq.c | 71
> +-
> 1 file changed, 62 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/cpufreq/tegra194-cpufreq.c
> b/drivers/cpufreq/tegra194-cpufreq.c
> index e1d931c..d250e49 100644
> --- a/drivers/cpufreq/tegra194-cpufreq.c
> +++ b/drivers/cpufreq/tegra194-cpufreq.c
> @@ -180,9 +180,70 @@ 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)
You weren't required to do this unnecessary change.
> +{
> + 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 tegra194_cpufreq_data *data = cpufreq_get_driver_data();
> + struct cpufreq_frequency_table *pos;
> + unsigned int rate;
> + u64 ndiv;
> + int ret;
> + u32 cl;
> +
> + if (!cpu_online(cpu))
This isn't required. The CPU is guaranteed to be online here.
> + return -EINVAL;
> +
> + smp_call_function_single(cpu, get_cpu_cluster, , true);
> +
> + if (cl >= data->num_clusters)
Is it really possible here ? I meant you must have already checked
this at cpufreq-init level already. Else mark it unlikely at least.
> + return -EINVAL;
> +
> + /* reconstruct actual cpu freq using counters */
> + rate = tegra194_get_speed_common(cpu, US_DELAY);
> +
> + /* get last written ndiv value */
> + ret = smp_call_function_single(cpu, get_cpu_ndiv, , true);
> + if (ret) {
What exactly can fail here ? get_cpu_ndiv() can't fail. Do we really
need this check ? What about WARN_ON_ONCE() ?
> + pr_err("cpufreq: Failed to get ndiv for CPU%d, ret:%d\n",
> +cpu, ret);
> + 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, data->tables[cl]) {
> + if (pos->driver_data != ndiv)
> + continue;
> +
> + if (abs(pos->frequency - rate) > 115200) {
where does this 115200 comes from ? Strange that it matches tty's baud
rate :)
This is 115 MHz, right ? Isn't that too big of a delta ?
> + pr_warn("cpufreq: cpu%d,cur:%u,set:%u,set ndiv:%llu\n",
> + cpu, rate, pos->frequency, ndiv);
> + } else {
> + rate = pos->frequency;
> + }
> + break;
> + }
> + return rate;
> }
--
viresh
