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 <sum...@nvidia.com>
> ---
> 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, &cl, 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, &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
