Re: [PATCH v2 2/2] cpufreq: tegra194: Fix unlisted boot freq warning

[Sumit Gupta]

> > Warning coming during boot because the boot freq set by bootloader
> > gets filtered out due to big freq steps while creating freq_table.
> > Fix this by setting closest higher frequency from freq_table.
> > Warning:
> >    cpufreq: cpufreq_online: CPU0: Running at unlisted freq
> >    cpufreq: cpufreq_online: CPU0: Unlisted initial frequency changed
> >
> > These warning messages also come during hotplug online of non-boot
> > CPU's while exiting from 'Suspend-to-RAM'. This happens because
> > during exit from 'Suspend-to-RAM', some time is taken to restore
> > last software requested CPU frequency written in register before
> > entering suspend.
>
> And who does this restoration ?
>
> > To fix this, adding online hook to wait till the
> > current frequency becomes equal or close to the last requested
> > frequency.
> >
> > Fixes: df320f89359c ("cpufreq: Add Tegra194 cpufreq driver")
> > Signed-off-by: Sumit Gupta <sumitg@xxxxxxxxxx>
> > ---
> >   drivers/cpufreq/tegra194-cpufreq.c | 86 ++++++++++++++++++++++++++++++++++----
> >   1 file changed, 79 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/cpufreq/tegra194-cpufreq.c b/drivers/cpufreq/tegra194-cpufreq.c
> > index d250e49..cc28b1e3 100644
> > --- a/drivers/cpufreq/tegra194-cpufreq.c
> > +++ b/drivers/cpufreq/tegra194-cpufreq.c
> > @@ -7,6 +7,7 @@
> >   #include <linux/cpufreq.h>
> >   #include <linux/delay.h>
> >   #include <linux/dma-mapping.h>
> > +#include <linux/iopoll.h>
> >   #include <linux/module.h>
> >   #include <linux/of.h>
> >   #include <linux/of_platform.h>
> > @@ -21,7 +22,6 @@
> >   #define KHZ                     1000
> >   #define REF_CLK_MHZ             408 /* 408 MHz */
> >   #define US_DELAY                500
> > -#define US_DELAY_MIN            2
> >   #define CPUFREQ_TBL_STEP_HZ     (50 * KHZ * KHZ)
> >   #define MAX_CNT                 ~0U
> >
> > @@ -249,17 +249,22 @@ static unsigned int tegra194_get_speed(u32 cpu)
> >   static int tegra194_cpufreq_init(struct cpufreq_policy *policy)
> >   {
> >        struct tegra194_cpufreq_data *data = cpufreq_get_driver_data();
> > -     u32 cpu;
> > +     u32 cpu = policy->cpu;
> > +     int ret;
> >        u32 cl;
> >
> > -     smp_call_function_single(policy->cpu, get_cpu_cluster, &cl, true);
> > +     if (!cpu_online(cpu))
>
> Not required to check this.
OK.

> > +             return -EINVAL;
> > +
> > +     ret = smp_call_function_single(cpu, get_cpu_cluster, &cl, true);
> > +     if (ret) {
>
> Same as in the other patch.
Got.

> > +             pr_err("cpufreq: Failed to get cluster for CPU%d\n", cpu);
> > +             return ret;
> > +     }
> >
> >        if (cl >= data->num_clusters)
> >                return -EINVAL;
> >
> > -     /* boot freq */
> > -     policy->cur = tegra194_get_speed_common(policy->cpu, US_DELAY_MIN);
> > -
> >        /* set same policy for all cpus in a cluster */
> >        for (cpu = (cl * 2); cpu < ((cl + 1) * 2); cpu++)
> >                cpumask_set_cpu(cpu, policy->cpus);
> > @@ -267,7 +272,23 @@ static int tegra194_cpufreq_init(struct cpufreq_policy *policy)
> >        policy->freq_table = data->tables[cl];
> >        policy->cpuinfo.transition_latency = TEGRA_CPUFREQ_TRANSITION_LATENCY;
> >
> > -     return 0;
> > +     policy->cur = tegra194_get_speed_common(policy->cpu, US_DELAY);
> > +
> > +     ret = cpufreq_table_validate_and_sort(policy);
> > +     if (ret)
> > +             return ret;
> > +
> > +     /* Are we running at unknown frequency ? */
> > +     ret = cpufreq_frequency_table_get_index(policy, policy->cur);
> > +     if (ret == -EINVAL) {
> > +             ret = __cpufreq_driver_target(policy, policy->cur - 1,
> > +                                           CPUFREQ_RELATION_L);
> > +             if (ret)
> > +                     return ret;
>
> > +             policy->cur = tegra194_get_speed_common(policy->cpu, US_DELAY);
>
> cpufreq-core will do this anyway, you don't need to do it.
Got.

> > +     }
> > +
> > +     return ret;
> >   }
>
> I wonder if I should change the pr_warn() in cpufreq-core to pr_info()
> instead, will that help you guys ? Will that still be a problem ? This
> is exactly same as what we do there.
Yes, this will also work. Then we don't need the current patch.
You want me to send a patch with change from pr_warn to pr_info?

> >   static int tegra194_cpufreq_set_target(struct cpufreq_policy *policy,
> > @@ -285,6 +306,55 @@ static int tegra194_cpufreq_set_target(struct cpufreq_policy *policy,
> >        return 0;
> >   }
> >
> > +static int tegra194_cpufreq_online(struct cpufreq_policy *policy)
> > +{
> > +     unsigned int interm_freq, last_set_freq;
> > +     struct cpufreq_frequency_table *pos;
> > +     u64 ndiv;
> > +     int ret;
> > +
> > +     if (!cpu_online(policy->cpu))
> > +             return -EINVAL;
> > +
> > +     /* get ndiv for the last frequency request from software  */
> > +     ret = smp_call_function_single(policy->cpu, get_cpu_ndiv, &ndiv, true);
> > +     if (ret) {
> > +             pr_err("cpufreq: Failed to get ndiv for CPU%d\n", policy->cpu);
> > +             return ret;
> > +     }
> > +
> > +     cpufreq_for_each_valid_entry(pos, policy->freq_table) {
> > +             if (pos->driver_data == ndiv) {
> > +                     last_set_freq = pos->frequency;
> > +                     break;
> > +             }
> > +     }
> > +
> > +     policy->cur = tegra194_get_speed_common(policy->cpu, US_DELAY);
> > +     interm_freq =  policy->cur;
> > +
> > +     /*
> > +      * It takes some time to restore the previous frequency while
> > +      * turning-on non-boot cores during exit from SC7(Suspend-to-RAM).
> > +      * So, wait till it reaches the previous value and timeout if the
> > +      * time taken to reach requested freq is >100ms
> > +      */
> > +     ret = read_poll_timeout(tegra194_get_speed_common, policy->cur,
> > +                             abs(policy->cur - last_set_freq) <= 115200, 0,
> > +                             100 * USEC_PER_MSEC, false, policy->cpu,
> > +                             US_DELAY);
>
> The firmware does this update ? Why do we need to wait for this ? I
> was actually suggesting an empty tegra194_cpufreq_online() routine
> here.
> > --
> viresh