1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3 * Windfarm PowerMac thermal control. Generic PID helpers
4 *
5 * (c) Copyright 2005 Benjamin Herrenschmidt, IBM Corp.
6 * <benh@kernel.crashing.org>
7 *
8 * This is a pair of generic PID helpers that can be used by
9 * control loops. One is the basic PID implementation, the
10 * other one is more specifically tailored to the loops used
11 * for CPU control with 2 input sample types (temp and power)
12 */
13
14 /*
15 * *** Simple PID ***
16 */
17
18 #define WF_PID_MAX_HISTORY 32
19
20 /* This parameter array is passed to the PID algorithm. Currently,
21 * we don't support changing parameters on the fly as it's not needed
22 * but could be implemented (with necessary adjustment of the history
23 * buffer
24 */
25 struct wf_pid_param {
26 int interval; /* Interval between samples in seconds */
27 int history_len; /* Size of history buffer */
28 int additive; /* 1: target relative to previous value */
29 s32 gd, gp, gr; /* PID gains */
30 s32 itarget; /* PID input target */
31 s32 min,max; /* min and max target values */
32 };
33
34 struct wf_pid_state {
35 int first; /* first run of the loop */
36 int index; /* index of current sample */
37 s32 target; /* current target value */
38 s32 samples[WF_PID_MAX_HISTORY]; /* samples history buffer */
39 s32 errors[WF_PID_MAX_HISTORY]; /* error history buffer */
40
41 struct wf_pid_param param;
42 };
43
44 extern void wf_pid_init(struct wf_pid_state *st, struct wf_pid_param *param);
45 extern s32 wf_pid_run(struct wf_pid_state *st, s32 sample);
46
47
48 /*
49 * *** CPU PID ***
50 */
51
52 #define WF_CPU_PID_MAX_HISTORY 32
53
54 /* This parameter array is passed to the CPU PID algorithm. Currently,
55 * we don't support changing parameters on the fly as it's not needed
56 * but could be implemented (with necessary adjustment of the history
57 * buffer
58 */
59 struct wf_cpu_pid_param {
60 int interval; /* Interval between samples in seconds */
61 int history_len; /* Size of history buffer */
62 s32 gd, gp, gr; /* PID gains */
63 s32 pmaxadj; /* PID max power adjust */
64 s32 ttarget; /* PID input target */
65 s32 tmax; /* PID input max */
66 s32 min,max; /* min and max target values */
67 };
68
69 struct wf_cpu_pid_state {
70 int first; /* first run of the loop */
71 int index; /* index of current power */
72 int tindex; /* index of current temp */
73 s32 target; /* current target value */
74 s32 last_delta; /* last Tactual - Ttarget */
75 s32 powers[WF_PID_MAX_HISTORY]; /* power history buffer */
76 s32 errors[WF_PID_MAX_HISTORY]; /* error history buffer */
77 s32 temps[2]; /* temp. history buffer */
78
79 struct wf_cpu_pid_param param;
80 };
81
82 extern void wf_cpu_pid_init(struct wf_cpu_pid_state *st,
83 struct wf_cpu_pid_param *param);
84 extern s32 wf_cpu_pid_run(struct wf_cpu_pid_state *st, s32 power, s32 temp);