[time] Add support for the ACPI power management timer
[ipxe.git] / src / arch / x86 / interface / pcbios / acpi_timer.c
1 /*
2 * Copyright (C) 2018 Michael Brown <mbrown@fensystems.co.uk>.
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License as
6 * published by the Free Software Foundation; either version 2 of the
7 * License, or any later version.
8 *
9 * This program is distributed in the hope that it will be useful, but
10 * WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
17 * 02110-1301, USA.
18 *
19 * You can also choose to distribute this program under the terms of
20 * the Unmodified Binary Distribution Licence (as given in the file
21 * COPYING.UBDL), provided that you have satisfied its requirements.
22 */
23
24 FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
25
26 #include <unistd.h>
27 #include <errno.h>
28 #include <assert.h>
29 #include <byteswap.h>
30 #include <ipxe/io.h>
31 #include <ipxe/acpi.h>
32
33 /** @file
34 *
35 * ACPI power management timer
36 *
37 */
38
39 /** ACPI timer frequency (fixed 3.579545MHz) */
40 #define ACPI_TIMER_HZ 3579545
41
42 /** ACPI timer mask
43 *
44 * Timers may be implemented as either 24-bit or 32-bit counters. We
45 * simplify the code by pessimistically assuming that the timer has
46 * only 24 bits.
47 */
48 #define ACPI_TIMER_MASK 0x00ffffffUL
49
50 /** Power management timer register address */
51 static unsigned int pm_tmr;
52
53 struct timer acpi_timer __timer ( TIMER_PREFERRED );
54
55 /**
56 * Get current system time in ticks
57 *
58 * @ret ticks Current time, in ticks
59 */
60 static unsigned long acpi_currticks ( void ) {
61 static unsigned long offset;
62 static uint32_t prev;
63 uint32_t now;
64
65 /* Read timer and account for wraparound */
66 now = ( inl ( pm_tmr ) & ACPI_TIMER_MASK );
67 if ( now < prev ) {
68 offset += ( ( ACPI_TIMER_MASK + 1 ) /
69 ( ACPI_TIMER_HZ / TICKS_PER_SEC ) );
70 }
71 prev = now;
72
73 /* Convert to timer ticks */
74 return ( offset + ( now / ( ACPI_TIMER_HZ / TICKS_PER_SEC ) ) );
75 }
76
77 /**
78 * Delay for a fixed number of microseconds
79 *
80 * @v usecs Number of microseconds for which to delay
81 */
82 static void acpi_udelay ( unsigned long usecs ) {
83 uint32_t start;
84 uint32_t elapsed;
85 uint32_t threshold;
86
87 /* Delay until a suitable number of ticks have elapsed. We do
88 * not need to allow for multiple wraparound, since the
89 * wraparound period for a 24-bit timer at 3.579545MHz is
90 * around 4700000us.
91 */
92 start = inl ( pm_tmr );
93 threshold = ( ( usecs * ACPI_TIMER_HZ ) / 1000000 );
94 do {
95 elapsed = ( ( inl ( pm_tmr ) - start ) & ACPI_TIMER_MASK );
96 } while ( elapsed < threshold );
97 }
98
99 /**
100 * Probe ACPI power management timer
101 *
102 * @ret rc Return status code
103 */
104 static int acpi_timer_probe ( void ) {
105 struct acpi_fadt fadtab;
106 userptr_t fadt;
107 unsigned int pm_tmr_blk;
108
109 /* Locate FADT */
110 fadt = acpi_find ( FADT_SIGNATURE, 0 );
111 if ( ! fadt ) {
112 DBGC ( &acpi_timer, "ACPI could not find FADT\n" );
113 return -ENOENT;
114 }
115
116 /* Read FADT */
117 copy_from_user ( &fadtab, fadt, 0, sizeof ( fadtab ) );
118 pm_tmr_blk = le32_to_cpu ( fadtab.pm_tmr_blk );
119 if ( ! pm_tmr_blk ) {
120 DBGC ( &acpi_timer, "ACPI has no timer\n" );
121 return -ENOENT;
122 }
123
124 /* Record power management timer register address */
125 pm_tmr = ( pm_tmr_blk + ACPI_PM_TMR );
126
127 return 0;
128 }
129
130 /** ACPI timer */
131 struct timer acpi_timer __timer ( TIMER_PREFERRED ) = {
132 .name = "acpi",
133 .probe = acpi_timer_probe,
134 .currticks = acpi_currticks,
135 .udelay = acpi_udelay,
136 };