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SubjectRe: [Patch 1/2] cpufreq: tegra194: get consistent cpuinfo_cur_freq
On 16-09-20, 22:41, 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 <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;

Maybe getting freq-table from cluster specific data would be better/faster.

> +
> + /* 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

Both have got the multi-line comments wrong. Format is wrong and every sentence
needs to start with a capital letter.

> + * 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);

Both of these can be merged in a single line I think. There is no need to print
delta as you already print both the frequencies.

> + } 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

--
viresh

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