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
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