1 /* $NetBSD: fpu.c,v 1.1 2011/11/15 12:23:22 tsutsui Exp $ */
2
3 /*-
4 * Copyright (c) 1996 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Gordon W. Ross.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 */
31
32 /*
33 * Floating Point Unit (MC68881/882/040/060)
34 * Probe for the FPU at early bootstrap.
35 */
36
37 #include <sys/cdefs.h>
38 __KERNEL_RCSID(0, "$NetBSD: fpu.c,v 1.1 2011/11/15 12:23:22 tsutsui Exp $");
39
40 #include <sys/param.h>
41 #include <sys/systm.h>
42 #include <sys/time.h>
43 #include <sys/kernel.h>
44 #include <sys/device.h>
45
46 #include <machine/psl.h>
47 #include <machine/cpu.h>
48 #include <machine/frame.h>
49
50 extern int *nofault;
51
52 int
fpu_probe(void)53 fpu_probe(void)
54 {
55 /*
56 * A 68881 idle frame is 28 bytes and a 68882's is 60 bytes.
57 * We, of course, need to have enough room for either.
58 */
59 struct fpframe fpframe;
60 label_t faultbuf;
61 uint8_t b;
62
63 nofault = (int *)&faultbuf;
64 if (setjmp(&faultbuf)) {
65 nofault = (int *)0;
66 return FPU_NONE;
67 }
68
69 /*
70 * Synchronize FPU or cause a fault.
71 * This should leave the 881/882 in the IDLE state,
72 * state, so we can determine which we have by
73 * examining the size of the FP state frame
74 */
75 __asm("fnop");
76
77 nofault = NULL;
78
79 /*
80 * Presumably, if we're an 040/060 and did not take exception
81 * above, we have an FPU. Don't bother probing.
82 */
83 if (cputype == CPU_68060)
84 return FPU_68060;
85 if (cputype == CPU_68040)
86 return FPU_68040;
87
88 /*
89 * Presumably, this will not cause a fault--the fnop should
90 * have if this will. We save the state in order to get the
91 * size of the frame.
92 */
93 __asm("fsave %0@" : : "a" (&fpframe) : "memory");
94
95 b = fpframe.fpf_fsize;
96
97 /*
98 * Now, restore a NULL state to reset the FPU.
99 */
100 fpframe.fpf_null = 0;
101 fpframe.fpf_idle.fpf_ccr = 0;
102 m68881_restore(&fpframe);
103
104 /*
105 * The size of a 68881 IDLE frame is 0x18
106 * and a 68882 frame is 0x38
107 */
108 if (b == 0x18)
109 return FPU_68881;
110 if (b == 0x38)
111 return FPU_68882;
112
113 /*
114 * If it's not one of the above, we have no clue what it is.
115 */
116 return FPU_UNKNOWN;
117 }
118