/*
   * 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);