1 /* 2 * Windfarm PowerMac thermal control. Generic PID helpers 3 * 4 * (c) Copyright 2005 Benjamin Herrenschmidt, IBM Corp. 5 * <benh@kernel.crashing.org> 6 * 7 * Released under the term of the GNU GPL v2. 8 * 9 * This is a pair of generic PID helpers that can be used by 10 * control loops. One is the basic PID implementation, the 11 * other one is more specifically tailored to the loops used 12 * for CPU control with 2 input sample types (temp and power) 13 */ 14 15 /* 16 * *** Simple PID *** 17 */ 18 19 #define WF_PID_MAX_HISTORY 32 20 21 /* This parameter array is passed to the PID algorithm. Currently, 22 * we don't support changing parameters on the fly as it's not needed 23 * but could be implemented (with necessary adjustment of the history 24 * buffer 25 */ 26 struct wf_pid_param { 27 int interval; /* Interval between samples in seconds */ 28 int history_len; /* Size of history buffer */ 29 int additive; /* 1: target relative to previous value */ 30 s32 gd, gp, gr; /* PID gains */ 31 s32 itarget; /* PID input target */ 32 s32 min,max; /* min and max target values */ 33 }; 34 35 struct wf_pid_state { 36 int first; /* first run of the loop */ 37 int index; /* index of current sample */ 38 s32 target; /* current target value */ 39 s32 samples[WF_PID_MAX_HISTORY]; /* samples history buffer */ 40 s32 errors[WF_PID_MAX_HISTORY]; /* error history buffer */ 41 42 struct wf_pid_param param; 43 }; 44 45 extern void wf_pid_init(struct wf_pid_state *st, struct wf_pid_param *param); 46 extern s32 wf_pid_run(struct wf_pid_state *st, s32 sample); 47 48 49 /* 50 * *** CPU PID *** 51 */ 52 53 #define WF_CPU_PID_MAX_HISTORY 32 54 55 /* This parameter array is passed to the CPU PID algorithm. Currently, 56 * we don't support changing parameters on the fly as it's not needed 57 * but could be implemented (with necessary adjustment of the history 58 * buffer 59 */ 60 struct wf_cpu_pid_param { 61 int interval; /* Interval between samples in seconds */ 62 int history_len; /* Size of history buffer */ 63 s32 gd, gp, gr; /* PID gains */ 64 s32 pmaxadj; /* PID max power adjust */ 65 s32 ttarget; /* PID input target */ 66 s32 tmax; /* PID input max */ 67 s32 min,max; /* min and max target values */ 68 }; 69 70 struct wf_cpu_pid_state { 71 int first; /* first run of the loop */ 72 int index; /* index of current power */ 73 int tindex; /* index of current temp */ 74 s32 target; /* current target value */ 75 s32 last_delta; /* last Tactual - Ttarget */ 76 s32 powers[WF_PID_MAX_HISTORY]; /* power history buffer */ 77 s32 errors[WF_PID_MAX_HISTORY]; /* error history buffer */ 78 s32 temps[2]; /* temp. history buffer */ 79 80 struct wf_cpu_pid_param param; 81 }; 82 83 extern void wf_cpu_pid_init(struct wf_cpu_pid_state *st, 84 struct wf_cpu_pid_param *param); 85 extern s32 wf_cpu_pid_run(struct wf_cpu_pid_state *st, s32 power, s32 temp); 86