Date:   Mon, 12 Oct 2020 11:43:35 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Sumit Gupta <sumitg@...dia.com>
Cc:     rjw@...ysocki.net, sudeep.holla@....com, thierry.reding@...il.com,
        jonathanh@...dia.com, linux-pm@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, ksitaraman@...dia.com,
        bbasu@...dia.com
Subject: Re: [PATCH v2 2/2] cpufreq: tegra194: Fix unlisted boot freq warning

On 08-10-20, 18:31, Sumit Gupta wrote:
> 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@...dia.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.

> +		return -EINVAL;
> +
> +	ret = smp_call_function_single(cpu, get_cpu_cluster, &cl, true);
> +	if (ret) {

Same as in the other patch.

> +		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.

> +	}
> +
> +	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.

>  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

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