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SubjectRe: [PATCH] cpufreq: ondemand: Introduces stepped frequency increase
Date
On Wed July 8 2009, Corrado Zoccolo wrote:
> The patch introduces a new sysfs tunable cpufreq/ondemand/freq_step,
> as found in conservative governor, to chose the frequency increase step,
> expressed as percentage (default = 100 is previous behaviour).
>
> This allows fine tuning powersaving on mobile CPUs, since smaller steps will allow to:
> * absorb punctual load spikes
> * stabilize at the needed frequency, without passing for more power consuming states, and
>

Has this been tested on VIA C7-M and similar VIA products?
Reason I ask is because they only step in increments of the
clock multiplier - which varies among the models.

Also, the factory recommendation is to stay on the freq/voltage
curve for each product.
Only the programmer accessable VID (Voltage IDentifier) codes
are (on-silicon) lookup table mapped to the VRM (Voltage Regulator Module)
control lines - not all products provide an "on curve" mapping
for each possible multiplier step.

How about a few conditional statements in this bit of code, please.

Mike
> Signed-off-by: Corrado Zoccolo czoccolo@gmail.com
>
> ---
> diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
> index e741c33..baa7b5e 100644
> --- a/drivers/cpufreq/cpufreq_ondemand.c
> +++ b/drivers/cpufreq/cpufreq_ondemand.c
> @@ -83,6 +83,7 @@ struct cpu_dbs_info_s {
> unsigned int freq_lo;
> unsigned int freq_lo_jiffies;
> unsigned int freq_hi_jiffies;
> + int requested_delta;
> int cpu;
> unsigned int enable:1,
> sample_type:1;
> @@ -112,11 +113,13 @@ static struct dbs_tuners {
> unsigned int down_differential;
> unsigned int ignore_nice;
> unsigned int powersave_bias;
> + unsigned int freq_step;
> } dbs_tuners_ins = {
> .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
> .down_differential = DEF_FREQUENCY_DOWN_DIFFERENTIAL,
> .ignore_nice = 0,
> .powersave_bias = 0,
> + .freq_step = 100,
> };
>
> static inline cputime64_t get_cpu_idle_time_jiffy(unsigned int cpu,
> @@ -261,6 +264,7 @@ show_one(sampling_rate, sampling_rate);
> show_one(up_threshold, up_threshold);
> show_one(ignore_nice_load, ignore_nice);
> show_one(powersave_bias, powersave_bias);
> +show_one(freq_step, freq_step);
>
> static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
> const char *buf, size_t count)
> @@ -358,6 +362,28 @@ static ssize_t store_powersave_bias(struct cpufreq_policy *unused,
> return count;
> }
>
> +static ssize_t store_freq_step(struct cpufreq_policy *policy,
> + const char *buf, size_t count)
> +{
> + unsigned int input;
> + int ret;
> + ret = sscanf(buf, "%u", &input);
> +
> + if (ret != 1)
> + return -EINVAL;
> +
> + if (input > 100)
> + input = 100;
> +
> + /* no need to test here if freq_step is zero as the user might actually
> + * want this, they would be crazy though :) */
> + mutex_lock(&dbs_mutex);
> + dbs_tuners_ins.freq_step = input;
> + mutex_unlock(&dbs_mutex);
> +
> + return count;
> +}
> +
> #define define_one_rw(_name) \
> static struct freq_attr _name = \
> __ATTR(_name, 0644, show_##_name, store_##_name)
> @@ -366,6 +392,7 @@ define_one_rw(sampling_rate);
> define_one_rw(up_threshold);
> define_one_rw(ignore_nice_load);
> define_one_rw(powersave_bias);
> +define_one_rw(freq_step);
>
> static struct attribute *dbs_attributes[] = {
> &sampling_rate_max.attr,
> @@ -374,6 +401,7 @@ static struct attribute *dbs_attributes[] = {
> &up_threshold.attr,
> &ignore_nice_load.attr,
> &powersave_bias.attr,
> + &freq_step.attr,
> NULL
> };
>
> @@ -464,19 +492,30 @@ static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
>
> /* Check for frequency increase */
> if (max_load_freq > dbs_tuners_ins.up_threshold * policy->cur) {
> + unsigned int freq_target = this_dbs_info->requested_delta
> + + policy->cur;
> + unsigned int freq_step;
> +
> /* if we are already at full speed then break out early */
> - if (!dbs_tuners_ins.powersave_bias) {
> - if (policy->cur == policy->max)
> - return;
> + if (freq_target == policy->max)
> + return;
> +
> + freq_step = (dbs_tuners_ins.freq_step * (policy->max-policy->min))
> + / 100;
>
> - __cpufreq_driver_target(policy, policy->max,
> - CPUFREQ_RELATION_H);
> + freq_target += max(freq_step, 5U);
> + freq_target = max(policy->min, min(policy->max, freq_target));
> +
> + if (!dbs_tuners_ins.powersave_bias) {
> + __cpufreq_driver_target(policy, freq_target,
> + CPUFREQ_RELATION_H);
> } else {
> - int freq = powersave_bias_target(policy, policy->max,
> - CPUFREQ_RELATION_H);
> + unsigned int freq = powersave_bias_target(policy, freq_target,
> + CPUFREQ_RELATION_H);
> __cpufreq_driver_target(policy, freq,
> CPUFREQ_RELATION_L);
> }
> + this_dbs_info->requested_delta = freq_target - policy->cur;
> return;
> }
>
> @@ -507,6 +546,7 @@ static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
> __cpufreq_driver_target(policy, freq,
> CPUFREQ_RELATION_L);
> }
> + this_dbs_info->requested_delta = freq_next - policy->cur;
> }
> }
>
>
> --
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