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SubjectRe: [PATCH v3] cpufreq: tegra194: get consistent cpuinfo_cur_freq
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>
> 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>
> ---
>
> Sending only this patch as other patch not required after the change
> to convert 'pr_warn' to 'pr_info' in cpufreq core for unlisted freq.
> Changelog
> v1[2] -> v3:
> - Removed unwanted checks for cpu_online and max cluster number
> - Used WARN_ON_ONCE to avoid print flooding.
>
> v1[1] -> v2:
> - Minor changes to improve comments and reduce debug prints.
> - Get freq table from cluster specific data instead of policy.
>
> [2] https://marc.info/?l=linux-tegra&m=160216218511280&w=2
> [1] https://marc.info/?l=linux-arm-kernel&m=160028821117535&w=2
>
> drivers/cpufreq/tegra194-cpufreq.c | 62 ++++++++++++++++++++++++++++++++------
> 1 file changed, 53 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/cpufreq/tegra194-cpufreq.c b/drivers/cpufreq/tegra194-cpufreq.c
> index e1d931c..7901587 100644
> --- a/drivers/cpufreq/tegra194-cpufreq.c
> +++ b/drivers/cpufreq/tegra194-cpufreq.c
> @@ -180,9 +180,61 @@ 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 tegra194_cpufreq_data *data = cpufreq_get_driver_data();
> + struct cpufreq_frequency_table *pos;
> + unsigned int rate;
> + u64 ndiv;
> + int ret;
> + u32 cl;
> +
> + smp_call_function_single(cpu, get_cpu_cluster, &cl, true);
> +
> + /* 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 (WARN_ON_ONCE(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) {
> + 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;
> }
>
> static int tegra194_cpufreq_init(struct cpufreq_policy *policy)
> @@ -209,14 +261,6 @@ 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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