1 /*
2 * Copyright (C) 2008 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., 675 Mass Ave, Cambridge, MA 02139, USA.
17 */
18
19 FILE_LICENCE ( GPL2_OR_LATER );
20
21 #include <limits.h>
22 #include <assert.h>
23 #include <unistd.h>
24 #include <gpxe/timer.h>
25 #include <gpxe/efi/efi.h>
26 #include <gpxe/efi/Protocol/Cpu.h>
27
28 /** @file
29 *
30 * gPXE timer API for EFI
31 *
32 */
33
34 /** Scale factor to apply to CPU timer 0
35 *
36 * The timer is scaled down in order to ensure that reasonable values
37 * for "number of ticks" don't exceed the size of an unsigned long.
38 */
39 #define EFI_TIMER0_SHIFT 12
40
41 /** Calibration time */
42 #define EFI_CALIBRATE_DELAY_MS 1
43
44 /** CPU protocol */
45 static EFI_CPU_ARCH_PROTOCOL *cpu_arch;
46 EFI_REQUIRE_PROTOCOL ( EFI_CPU_ARCH_PROTOCOL, &cpu_arch );
47
48 /**
49 * Delay for a fixed number of microseconds
50 *
51 * @v usecs Number of microseconds for which to delay
52 */
efi_udelay(unsigned long usecs)53 static void efi_udelay ( unsigned long usecs ) {
54 EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
55 EFI_STATUS efirc;
56
57 if ( ( efirc = bs->Stall ( usecs ) ) != 0 ) {
58 DBG ( "EFI could not delay for %ldus: %s\n",
59 usecs, efi_strerror ( efirc ) );
60 /* Probably screwed */
61 }
62 }
63
64 /**
65 * Get current system time in ticks
66 *
67 * @ret ticks Current time, in ticks
68 */
efi_currticks(void)69 static unsigned long efi_currticks ( void ) {
70 UINT64 time;
71 EFI_STATUS efirc;
72
73 /* Read CPU timer 0 (TSC) */
74 if ( ( efirc = cpu_arch->GetTimerValue ( cpu_arch, 0, &time,
75 NULL ) ) != 0 ) {
76 DBG ( "EFI could not read CPU timer: %s\n",
77 efi_strerror ( efirc ) );
78 /* Probably screwed */
79 return -1UL;
80 }
81
82 return ( time >> EFI_TIMER0_SHIFT );
83 }
84
85 /**
86 * Get number of ticks per second
87 *
88 * @ret ticks_per_sec Number of ticks per second
89 */
efi_ticks_per_sec(void)90 static unsigned long efi_ticks_per_sec ( void ) {
91 static unsigned long ticks_per_sec = 0;
92
93 /* Calibrate timer, if necessary. EFI does nominally provide
94 * the timer speed via the (optional) TimerPeriod parameter to
95 * the GetTimerValue() call, but it gets the speed slightly
96 * wrong. By up to three orders of magnitude. Not helpful.
97 */
98 if ( ! ticks_per_sec ) {
99 unsigned long start;
100 unsigned long elapsed;
101
102 DBG ( "Calibrating EFI timer with a %d ms delay\n",
103 EFI_CALIBRATE_DELAY_MS );
104 start = currticks();
105 mdelay ( EFI_CALIBRATE_DELAY_MS );
106 elapsed = ( currticks() - start );
107 ticks_per_sec = ( elapsed * ( 1000 / EFI_CALIBRATE_DELAY_MS ));
108 DBG ( "EFI CPU timer calibrated at %ld ticks in %d ms (%ld "
109 "ticks/sec)\n", elapsed, EFI_CALIBRATE_DELAY_MS,
110 ticks_per_sec );
111 }
112
113 return ticks_per_sec;
114 }
115
116 PROVIDE_TIMER ( efi, udelay, efi_udelay );
117 PROVIDE_TIMER ( efi, currticks, efi_currticks );
118 PROVIDE_TIMER ( efi, ticks_per_sec, efi_ticks_per_sec );
119