include/asm-i386/mc146818rtc.h

   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 <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 #ifdef __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                         continue;
  48                 if (__cmpxchg(&cmos_lock, 0, new, sizeof(cmos_lock)) == 0)
  49                         return;
  50         }
  51 }
  52
  53 static inline void unlock_cmos(void)
  54 {
  55         cmos_lock = 0;
  56 }
  57 static inline int do_i_have_lock_cmos(void)
  58 {
  59         return (cmos_lock >> 8) == (smp_processor_id()+1);
  60 }
  61 static inline unsigned char current_lock_cmos_reg(void)
  62 {
  63         return cmos_lock & 0xff;
  64 }
  65 #define lock_cmos_prefix(reg) \
  66         do {                                    \
  67                 unsigned long cmos_flags;       \
  68                 local_irq_save(cmos_flags);     \
  69                 lock_cmos(reg)
  70 #define lock_cmos_suffix(reg) \
  71                 unlock_cmos();                  \
  72                 local_irq_restore(cmos_flags);  \
  73         } while (0)
  74 #else
  75 #define lock_cmos_prefix(reg) do {} while (0)
  76 #define lock_cmos_suffix(reg) do {} while (0)
  77 #define lock_cmos(reg)
  78 #define unlock_cmos()
  79 #define do_i_have_lock_cmos() 0
  80 #define current_lock_cmos_reg() 0
  81 #endif
  82
  83 /*
  84  * The yet supported machines all access the RTC index register via
  85  * an ISA port access but the way to access the date register differs ...
  86  */
  87 #define CMOS_READ(addr) rtc_cmos_read(addr)
  88 #define CMOS_WRITE(val, addr) rtc_cmos_write(val, addr)
  89 unsigned char rtc_cmos_read(unsigned char addr);
  90 void rtc_cmos_write(unsigned char val, unsigned char addr);
  91
  92 #define RTC_IRQ 8
  93
  94 #endif /* _ASM_MC146818RTC_H */