drivers/thermal/cpuidle_cooling.c

Source file repositories/reference/linux-study-clean/drivers/thermal/cpuidle_cooling.c

File Facts

System
Linux kernel
Corpus path
drivers/thermal/cpuidle_cooling.c
Extension
.c
Size
7432 bytes
Lines
271
Domain
Driver Families
Bucket
drivers/thermal
Inferred role
Driver Families: implementation source
Status
source implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

struct cpuidle_cooling_device {
	struct idle_inject_device *ii_dev;
	unsigned long state;
};

/**
 * cpuidle_cooling_runtime - Running time computation
 * @idle_duration_us: CPU idle time to inject in microseconds
 * @state: a percentile based number
 *
 * The running duration is computed from the idle injection duration
 * which is fixed. If we reach 100% of idle injection ratio, that
 * means the running duration is zero. If we have a 50% ratio
 * injection, that means we have equal duration for idle and for
 * running duration.
 *
 * The formula is deduced as follows:
 *
 *  running = idle x ((100 / ratio) - 1)
 *
 * For precision purpose for integer math, we use the following:
 *
 *  running = (idle x 100) / ratio - idle
 *
 * For example, if we have an injected duration of 50%, then we end up
 * with 10ms of idle injection and 10ms of running duration.
 *
 * Return: An unsigned int for a usec based runtime duration.
 */
static unsigned int cpuidle_cooling_runtime(unsigned int idle_duration_us,
					    unsigned long state)
{
	if (!state)
		return 0;

	return ((idle_duration_us * 100) / state) - idle_duration_us;
}

/**
 * cpuidle_cooling_get_max_state - Get the maximum state
 * @cdev  : the thermal cooling device
 * @state : a pointer to the state variable to be filled
 *
 * The function always returns 100 as the injection ratio. It is
 * percentile based for consistency across different platforms.
 *
 * Return: The function can not fail, it is always zero
 */
static int cpuidle_cooling_get_max_state(struct thermal_cooling_device *cdev,
					 unsigned long *state)
{
	/*
	 * Depending on the configuration or the hardware, the running
	 * cycle and the idle cycle could be different. We want to
	 * unify that to an 0..100 interval, so the set state
	 * interface will be the same whatever the platform is.
	 *
	 * The state 100% will make the cluster 100% ... idle. A 0%
	 * injection ratio means no idle injection at all and 50%
	 * means for 10ms of idle injection, we have 10ms of running
	 * time.
	 */
	*state = 100;

	return 0;
}

/**
 * cpuidle_cooling_get_cur_state - Get the current cooling state
 * @cdev: the thermal cooling device
 * @state: a pointer to the state
 *
 * The function just copies  the state value from the private thermal
 * cooling device structure, the mapping is 1 <-> 1.
 *
 * Return: The function can not fail, it is always zero
 */
static int cpuidle_cooling_get_cur_state(struct thermal_cooling_device *cdev,
					 unsigned long *state)
{
	struct cpuidle_cooling_device *idle_cdev = cdev->devdata;

	*state = idle_cdev->state;

	return 0;
}

/**
 * cpuidle_cooling_set_cur_state - Set the current cooling state
 * @cdev: the thermal cooling device

Annotation

Implementation Notes