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

[Sumit Gupta <sumitg@nvidia.com>]

>> 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@nvidia.com>
>> ---
>>   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
>