1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3 * Machine dependent access functions for RTC registers.
4 */
5 #ifndef _ASM_X86_MC146818RTC_H
6 #define _ASM_X86_MC146818RTC_H
7
8 #include <asm/io.h>
9 #include <asm/processor.h>
10
11 #ifndef RTC_PORT
12 #define RTC_PORT(x) (0x70 + (x))
13 #define RTC_ALWAYS_BCD 1 /* RTC operates in binary mode */
14 #endif
15
16 #if defined(CONFIG_X86_32)
17 /*
18 * This lock provides nmi access to the CMOS/RTC registers. It has some
19 * special properties. It is owned by a CPU and stores the index register
20 * currently being accessed (if owned). The idea here is that it works
21 * like a normal lock (normally). However, in an NMI, the NMI code will
22 * first check to see if its CPU owns the lock, meaning that the NMI
23 * interrupted during the read/write of the device. If it does, it goes ahead
24 * and performs the access and then restores the index register. If it does
25 * not, it locks normally.
26 *
27 * Note that since we are working with NMIs, we need this lock even in
28 * a non-SMP machine just to mark that the lock is owned.
29 *
30 * This only works with compare-and-swap. There is no other way to
31 * atomically claim the lock and set the owner.
32 */
33 #include <linux/smp.h>
34 extern volatile unsigned long cmos_lock;
35
36 /*
37 * All of these below must be called with interrupts off, preempt
38 * disabled, etc.
39 */
40
lock_cmos(unsigned char reg)41 static inline void lock_cmos(unsigned char reg)
42 {
43 unsigned long new;
44 new = ((smp_processor_id() + 1) << 8) | reg;
45 for (;;) {
46 if (cmos_lock) {
47 cpu_relax();
48 continue;
49 }
50 if (__cmpxchg(&cmos_lock, 0, new, sizeof(cmos_lock)) == 0)
51 return;
52 }
53 }
54
unlock_cmos(void)55 static inline void unlock_cmos(void)
56 {
57 cmos_lock = 0;
58 }
59
do_i_have_lock_cmos(void)60 static inline int do_i_have_lock_cmos(void)
61 {
62 return (cmos_lock >> 8) == (smp_processor_id() + 1);
63 }
64
current_lock_cmos_reg(void)65 static inline unsigned char current_lock_cmos_reg(void)
66 {
67 return cmos_lock & 0xff;
68 }
69
70 #define lock_cmos_prefix(reg) \
71 do { \
72 unsigned long cmos_flags; \
73 local_irq_save(cmos_flags); \
74 lock_cmos(reg)
75
76 #define lock_cmos_suffix(reg) \
77 unlock_cmos(); \
78 local_irq_restore(cmos_flags); \
79 } while (0)
80 #else
81 #define lock_cmos_prefix(reg) do {} while (0)
82 #define lock_cmos_suffix(reg) do {} while (0)
83 #define lock_cmos(reg) do { } while (0)
84 #define unlock_cmos() do { } while (0)
85 #define do_i_have_lock_cmos() 0
86 #define current_lock_cmos_reg() 0
87 #endif
88
89 /*
90 * The yet supported machines all access the RTC index register via
91 * an ISA port access but the way to access the date register differs ...
92 */
93 #define CMOS_READ(addr) rtc_cmos_read(addr)
94 #define CMOS_WRITE(val, addr) rtc_cmos_write(val, addr)
95 unsigned char rtc_cmos_read(unsigned char addr);
96 void rtc_cmos_write(unsigned char val, unsigned char addr);
97
98 extern int mach_set_cmos_time(const struct timespec64 *now);
99 extern void mach_get_cmos_time(struct timespec64 *now);
100
101 #define RTC_IRQ 8
102
103 #endif /* _ASM_X86_MC146818RTC_H */
104