2 * Windfarm PowerMac thermal control. Generic PID helpers
4 * (c) Copyright 2005 Benjamin Herrenschmidt, IBM Corp.
5 * <benh@kernel.crashing.org>
7 * Released under the term of the GNU GPL v2.
10 #include <linux/types.h>
11 #include <linux/errno.h>
12 #include <linux/kernel.h>
13 #include <linux/string.h>
14 #include <linux/module.h>
16 #include "windfarm_pid.h"
21 #define DBG(args...) printk(args)
23 #define DBG(args...) do { } while(0)
26 void wf_pid_init(struct wf_pid_state
*st
, struct wf_pid_param
*param
)
28 memset(st
, 0, sizeof(struct wf_pid_state
));
32 EXPORT_SYMBOL_GPL(wf_pid_init
);
34 s32
wf_pid_run(struct wf_pid_state
*st
, s32 new_sample
)
36 s64 error
, integ
, deriv
;
38 int i
, hlen
= st
->param
.history_len
;
40 /* Calculate error term */
41 error
= new_sample
- st
->param
.itarget
;
43 /* Get samples into our history buffer */
45 for (i
= 0; i
< hlen
; i
++) {
46 st
->samples
[i
] = new_sample
;
47 st
->errors
[i
] = error
;
52 st
->index
= (st
->index
+ 1) % hlen
;
53 st
->samples
[st
->index
] = new_sample
;
54 st
->errors
[st
->index
] = error
;
57 /* Calculate integral term */
58 for (i
= 0, integ
= 0; i
< hlen
; i
++)
59 integ
+= st
->errors
[(st
->index
+ hlen
- i
) % hlen
];
60 integ
*= st
->param
.interval
;
62 /* Calculate derivative term */
63 deriv
= st
->errors
[st
->index
] -
64 st
->errors
[(st
->index
+ hlen
- 1) % hlen
];
65 deriv
/= st
->param
.interval
;
67 /* Calculate target */
68 target
= (s32
)((integ
* (s64
)st
->param
.gr
+ deriv
* (s64
)st
->param
.gd
+
69 error
* (s64
)st
->param
.gp
) >> 36);
70 if (st
->param
.additive
)
72 target
= max(target
, st
->param
.min
);
73 target
= min(target
, st
->param
.max
);
78 EXPORT_SYMBOL_GPL(wf_pid_run
);
80 void wf_cpu_pid_init(struct wf_cpu_pid_state
*st
,
81 struct wf_cpu_pid_param
*param
)
83 memset(st
, 0, sizeof(struct wf_cpu_pid_state
));
87 EXPORT_SYMBOL_GPL(wf_cpu_pid_init
);
89 s32
wf_cpu_pid_run(struct wf_cpu_pid_state
*st
, s32 new_power
, s32 new_temp
)
91 s64 integ
, deriv
, prop
;
92 s32 error
, target
, sval
, adj
;
93 int i
, hlen
= st
->param
.history_len
;
95 /* Calculate error term */
96 error
= st
->param
.pmaxadj
- new_power
;
98 /* Get samples into our history buffer */
100 for (i
= 0; i
< hlen
; i
++) {
101 st
->powers
[i
] = new_power
;
102 st
->errors
[i
] = error
;
104 st
->temps
[0] = st
->temps
[1] = new_temp
;
106 st
->index
= st
->tindex
= 0;
108 st
->index
= (st
->index
+ 1) % hlen
;
109 st
->powers
[st
->index
] = new_power
;
110 st
->errors
[st
->index
] = error
;
111 st
->tindex
= (st
->tindex
+ 1) % 2;
112 st
->temps
[st
->tindex
] = new_temp
;
115 /* Calculate integral term */
116 for (i
= 0, integ
= 0; i
< hlen
; i
++)
117 integ
+= st
->errors
[(st
->index
+ hlen
- i
) % hlen
];
118 integ
*= st
->param
.interval
;
119 integ
*= st
->param
.gr
;
120 sval
= st
->param
.tmax
- (s32
)(integ
>> 20);
121 adj
= min(st
->param
.ttarget
, sval
);
123 DBG("integ: %lx, sval: %lx, adj: %lx\n", integ
, sval
, adj
);
125 /* Calculate derivative term */
126 deriv
= st
->temps
[st
->tindex
] -
127 st
->temps
[(st
->tindex
+ 2 - 1) % 2];
128 deriv
/= st
->param
.interval
;
129 deriv
*= st
->param
.gd
;
131 /* Calculate proportional term */
132 prop
= st
->last_delta
= (new_temp
- adj
);
133 prop
*= st
->param
.gp
;
135 DBG("deriv: %lx, prop: %lx\n", deriv
, prop
);
137 /* Calculate target */
138 target
= st
->target
+ (s32
)((deriv
+ prop
) >> 36);
139 target
= max(target
, st
->param
.min
);
140 target
= min(target
, st
->param
.max
);
145 EXPORT_SYMBOL_GPL(wf_cpu_pid_run
);
147 MODULE_AUTHOR("Benjamin Herrenschmidt <benh@kernel.crashing.org>");
148 MODULE_DESCRIPTION("PID algorithm for PowerMacs thermal control");
149 MODULE_LICENSE("GPL");
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