xref: /openbmc/linux/arch/x86/boot/apm.c (revision 22246614)
1 /* -*- linux-c -*- ------------------------------------------------------- *
2  *
3  *   Copyright (C) 1991, 1992 Linus Torvalds
4  *   Copyright 2007 rPath, Inc. - All Rights Reserved
5  *
6  *   Original APM BIOS checking by Stephen Rothwell, May 1994
7  *   (sfr@canb.auug.org.au)
8  *
9  *   This file is part of the Linux kernel, and is made available under
10  *   the terms of the GNU General Public License version 2.
11  *
12  * ----------------------------------------------------------------------- */
13 
14 /*
15  * Get APM BIOS information
16  */
17 
18 #include "boot.h"
19 
20 int query_apm_bios(void)
21 {
22 	u16 ax, bx, cx, dx, di;
23 	u32 ebx, esi;
24 	u8 err;
25 
26 	/* APM BIOS installation check */
27 	ax = 0x5300;
28 	bx = cx = 0;
29 	asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp ; setc %0"
30 		     : "=d" (err), "+a" (ax), "+b" (bx), "+c" (cx)
31 		     : : "esi", "edi");
32 
33 	if (err)
34 		return -1;		/* No APM BIOS */
35 
36 	if (bx != 0x504d)	/* "PM" signature */
37 		return -1;
38 
39 	if (!(cx & 0x02))		/* 32 bits supported? */
40 		return -1;
41 
42 	/* Disconnect first, just in case */
43 	ax = 0x5304;
44 	bx = 0;
45 	asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp"
46 		     : "+a" (ax), "+b" (bx)
47 		     : : "ecx", "edx", "esi", "edi");
48 
49 	/* Paranoia */
50 	ebx = esi = 0;
51 	cx = dx = di = 0;
52 
53 	/* 32-bit connect */
54 	asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp ; setc %6"
55 		     : "=a" (ax), "+b" (ebx), "+c" (cx), "+d" (dx),
56 		       "+S" (esi), "+D" (di), "=m" (err)
57 		     : "a" (0x5303));
58 
59 	boot_params.apm_bios_info.cseg = ax;
60 	boot_params.apm_bios_info.offset = ebx;
61 	boot_params.apm_bios_info.cseg_16 = cx;
62 	boot_params.apm_bios_info.dseg = dx;
63 	boot_params.apm_bios_info.cseg_len = (u16)esi;
64 	boot_params.apm_bios_info.cseg_16_len = esi >> 16;
65 	boot_params.apm_bios_info.dseg_len = di;
66 
67 	if (err)
68 		return -1;
69 
70 	/* Redo the installation check as the 32-bit connect;
71 	   some BIOSes return different flags this way... */
72 
73 	ax = 0x5300;
74 	bx = cx = 0;
75 	asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp ; setc %0"
76 		     : "=d" (err), "+a" (ax), "+b" (bx), "+c" (cx)
77 		     : : "esi", "edi");
78 
79 	if (err || bx != 0x504d) {
80 		/* Failure with 32-bit connect, try to disconect and ignore */
81 		ax = 0x5304;
82 		bx = 0;
83 		asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp"
84 			     : "+a" (ax), "+b" (bx)
85 			     : : "ecx", "edx", "esi", "edi");
86 		return -1;
87 	}
88 
89 	boot_params.apm_bios_info.version = ax;
90 	boot_params.apm_bios_info.flags = cx;
91 	return 0;
92 }
93 
94