arch/x86/include/asm/mc146818rtc.h

   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
  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(const struct timespec *now);
  99 extern void mach_get_cmos_time(struct timespec *now);
 100
 101 #define RTC_IRQ 8
 102
 103 #endif /* _ASM_X86_MC146818RTC_H */