Hi,
On Friday, May 27, 2011, MyungJoo Ham wrote:
> Three CPUFREQ-like governors are provided as examples.
>
> powersave: use the lowest frequency possible. The user (device) should
> set the polling_ms as 0 because polling is useless for this governor.
>
> performance: use the highest freqeuncy possible. The user (device)
> should set the polling_ms as 0 because polling is useless for this
> governor.
>
> simple_ondemand: simplified version of CPUFREQ's ONDEMAND governor.
>
> When a user updates OPP entries (enable/disable/add), OPP framework
> automatically notifies DEVFREQ to update operating frequency
> accordingly. Thus, DEVFREQ users (device drivers) do not need to update
> DEVFREQ manually with OPP entry updates or set polling_ms for powersave
> , performance, or any other "static" governors.
>
> Signed-off-by: MyungJoo Ham <myungjoo.ham@xxxxxxxxxxx>
> Signed-off-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
> ---
> drivers/base/power/devfreq.c | 69 ++++++++++++++++++++++++++++++++++++++++++
> include/linux/devfreq.h | 5 +++
> 2 files changed, 74 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/base/power/devfreq.c b/drivers/base/power/devfreq.c
> index 883d953..7648a94 100644
> --- a/drivers/base/power/devfreq.c
> +++ b/drivers/base/power/devfreq.c
> @@ -395,3 +395,72 @@ static int __init devfreq_init(void)
> return 0;
> }
> late_initcall(devfreq_init);
> +
> +static int devfreq_powersave_func(struct devfreq *df,
> + unsigned long *freq)
> +{
> + *freq = 0; /* devfreq_do will run "ceiling" to 0 */
> + return 0;
> +}
> +
> +struct devfreq_governor devfreq_powersave = {
> + .get_target_freq = devfreq_powersave_func,
> +};
> +
> +static int devfreq_performance_func(struct devfreq *df,
> + unsigned long *freq)
> +{
> + *freq = UINT_MAX; /* devfreq_do will run "floor" */
> + return 0;
> +}
> +
> +struct devfreq_governor devfreq_performance = {
> + .get_target_freq = devfreq_performance_func,
> +};
> +
> +/* Constants for DevFreq-Simple-Ondemand (DFSO) */
> +#define DFSO_UPTHRESHOLD (90)
> +#define DFSO_DOWNDIFFERENCTIAL (5)
> +static int devfreq_simple_ondemand_func(struct devfreq *df,
> + unsigned long *freq)
> +{
> + struct devfreq_dev_status stat;
> + int err = df->profile->get_dev_status(df->dev, &stat);
> + unsigned long long a, b;
> +
> + if (err)
> + return err;
> +
> + /* Set MAX if it's busy enough */
> + if (stat.busy_time * 100 >
> + stat.total_time * DFSO_UPTHRESHOLD) {
> + *freq = UINT_MAX;
> + return 0;
> + }
> +
> + /* Set MAX if we do not know the initial frequency */
> + if (stat.current_frequency == 0) {
> + *freq = UINT_MAX;
> + return 0;
> + }
> +
> + /* Keep the current frequency */
> + if (stat.busy_time * 100 >
> + stat.total_time * (DFSO_UPTHRESHOLD - DFSO_DOWNDIFFERENCTIAL)) {
> + *freq = stat.current_frequency;
> + return 0;
> + }
> +
> + /* Set the desired frequency based on the load */
> + a = (unsigned long long) stat.busy_time * stat.current_frequency;
What's the purpose of the conversion?
> + b = div_u64(a, stat.total_time);
> + b *= 100;
> + b = div_u64(b, (DFSO_UPTHRESHOLD - DFSO_DOWNDIFFERENCTIAL / 2));
> + *freq = (unsigned long) b;
> +
> + return 0;
> +}
Rafael
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