Re: [Patch 1/2] cpufreq: tegra194: get consistent cpuinfo_cur_freq

[Sumit Gupta]

> > 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@xxxxxxxxxx>
> > ---
> >   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.
will do the change in next patch version.

> > +
> > +     /* 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.
will correct.

> > +      * 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.
Will do this also in next patch version.

> > +             } 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