1 /*
2 * Machine dependent access functions for RTC registers.
3 */
4 #ifndef _ASM_MC146818RTC_H
5 #define _ASM_MC146818RTC_H
6
7 #include <asm/io.h>
8 #include <asm/system.h>
9 #include <asm/processor.h>
10 #include <linux/mc146818rtc.h>
11
12 #ifndef RTC_PORT
13 #define RTC_PORT(x) (0x70 + (x))
14 #define RTC_ALWAYS_BCD 1 /* RTC operates in binary mode */
15 #endif
16
17 #ifdef __HAVE_ARCH_CMPXCHG
18 /*
19 * This lock provides nmi access to the CMOS/RTC registers. It has some
20 * special properties. It is owned by a CPU and stores the index register
21 * currently being accessed (if owned). The idea here is that it works
22 * like a normal lock (normally). However, in an NMI, the NMI code will
23 * first check to see if its CPU owns the lock, meaning that the NMI
24 * interrupted during the read/write of the device. If it does, it goes ahead
25 * and performs the access and then restores the index register. If it does
26 * not, it locks normally.
27 *
28 * Note that since we are working with NMIs, we need this lock even in
29 * a non-SMP machine just to mark that the lock is owned.
30 *
31 * This only works with compare-and-swap. There is no other way to
32 * atomically claim the lock and set the owner.
33 */
34 #include <linux/smp.h>
35 extern volatile unsigned long cmos_lock;
36
37 /*
38 * All of these below must be called with interrupts off, preempt
39 * disabled, etc.
40 */
41
lock_cmos(unsigned char reg)42 static inline void lock_cmos(unsigned char reg)
43 {
44 unsigned long new;
45 new = ((smp_processor_id()+1) << 8) | reg;
46 for (;;) {
47 if (cmos_lock) {
48 cpu_relax();
49 continue;
50 }
51 if (__cmpxchg(&cmos_lock, 0, new, sizeof(cmos_lock)) == 0)
52 return;
53 }
54 }
55
unlock_cmos(void)56 static inline void unlock_cmos(void)
57 {
58 cmos_lock = 0;
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 }
current_lock_cmos_reg(void)64 static inline unsigned char current_lock_cmos_reg(void)
65 {
66 return cmos_lock & 0xff;
67 }
68 #define lock_cmos_prefix(reg) \
69 do { \
70 unsigned long cmos_flags; \
71 local_irq_save(cmos_flags); \
72 lock_cmos(reg)
73 #define lock_cmos_suffix(reg) \
74 unlock_cmos(); \
75 local_irq_restore(cmos_flags); \
76 } while (0)
77 #else
78 #define lock_cmos_prefix(reg) do {} while (0)
79 #define lock_cmos_suffix(reg) do {} while (0)
80 #define lock_cmos(reg)
81 #define unlock_cmos()
82 #define do_i_have_lock_cmos() 0
83 #define current_lock_cmos_reg() 0
84 #endif
85
86 /*
87 * The yet supported machines all access the RTC index register via
88 * an ISA port access but the way to access the date register differs ...
89 */
90 #define CMOS_READ(addr) rtc_cmos_read(addr)
91 #define CMOS_WRITE(val, addr) rtc_cmos_write(val, addr)
92 unsigned char rtc_cmos_read(unsigned char addr);
93 void rtc_cmos_write(unsigned char val, unsigned char addr);
94
95 #define RTC_IRQ 8
96
97 #endif /* _ASM_MC146818RTC_H */
98