windfarm_pid.h

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/*
 * Windfarm PowerMac thermal control. Generic PID helpers
 *
 * (c) Copyright 2005 Benjamin Herrenschmidt, IBM Corp.
 *                    <[email protected]>
 *
 * 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);