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mc146818rtc.h
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1 /*
2  * Machine dependent access functions for RTC registers.
3  */
4 #ifndef _ASM_X86_MC146818RTC_H
5 #define _ASM_X86_MC146818RTC_H
6 
7 #include <asm/io.h>
8 #include <asm/processor.h>
9 #include <linux/mc146818rtc.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) && defined(__HAVE_ARCH_CMPXCHG)
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 
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 
55 static inline void unlock_cmos(void)
56 {
57  cmos_lock = 0;
58 }
59 
60 static inline int do_i_have_lock_cmos(void)
61 {
62  return (cmos_lock >> 8) == (smp_processor_id() + 1);
63 }
64 
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_rtc_mmss(unsigned long nowtime);
99 extern unsigned long mach_get_cmos_time(void);
100 
101 #define RTC_IRQ 8
102 
103 #endif /* _ASM_X86_MC146818RTC_H */