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/*
* Windfarm PowerMac thermal control. Generic PID helpers
*
* (c) Copyright 2005 Benjamin Herrenschmidt, IBM Corp.
* <benh@kernel.crashing.org>
*
* Released under the term of the GNU GPL v2.
*
* This is a pair of generic PID helpers that can be used by
* control loops. One is the basic PID implementation, the
* other one is more specifically tailored to the loops used
* for CPU control with 2 input sample types (temp and power)
*/
/*
* *** Simple PID ***
*/
#define WF_PID_MAX_HISTORY 32
/* This parameter array is passed to the PID algorithm. Currently,
* we don't support changing parameters on the fly as it's not needed
* but could be implemented (with necessary adjustment of the history
* buffer
*/
struct wf_pid_param {
int interval; /* Interval between samples in seconds */
int history_len; /* Size of history buffer */
int additive; /* 1: target relative to previous value */
s32 gd, gp, gr; /* PID gains */
s32 itarget; /* PID input target */
s32 min,max; /* min and max target values */
};
struct wf_pid_state {
int first; /* first run of the loop */
int index; /* index of current sample */
s32 target; /* current target value */
s32 samples[WF_PID_MAX_HISTORY]; /* samples history buffer */
s32 errors[WF_PID_MAX_HISTORY]; /* error history buffer */
struct wf_pid_param param;
};
extern void wf_pid_init(struct wf_pid_state *st, struct wf_pid_param *param);
extern s32 wf_pid_run(struct wf_pid_state *st, s32 sample);
/*
* *** CPU PID ***
*/
#define WF_CPU_PID_MAX_HISTORY 32
/* This parameter array is passed to the CPU PID algorithm. Currently,
* we don't support changing parameters on the fly as it's not needed
* but could be implemented (with necessary adjustment of the history
* buffer
*/
struct wf_cpu_pid_param {
int interval; /* Interval between samples in seconds */
int history_len; /* Size of history buffer */
s32 gd, gp, gr; /* PID gains */
s32 pmaxadj; /* PID max power adjust */
s32 ttarget; /* PID input target */
s32 tmax; /* PID input max */
s32 min,max; /* min and max target values */
};
struct wf_cpu_pid_state {
int first; /* first run of the loop */
int index; /* index of current power */
int tindex; /* index of current temp */
s32 target; /* current target value */
s32 last_delta; /* last Tactual - Ttarget */
s32 powers[WF_PID_MAX_HISTORY]; /* power history buffer */
s32 errors[WF_PID_MAX_HISTORY]; /* error history buffer */
s32 temps[2]; /* temp. history buffer */
struct wf_cpu_pid_param param;
};
extern void wf_cpu_pid_init(struct wf_cpu_pid_state *st,
struct wf_cpu_pid_param *param);
extern s32 wf_cpu_pid_run(struct wf_cpu_pid_state *st, s32 power, s32 temp);
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