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>
 34extern volatile unsigned long cmos_lock;
 35
 36/*
 37 * All of these below must be called with interrupts off, preempt
 38 * disabled, etc.
 39 */
 40
 41static 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
 55static inline void unlock_cmos(void)
 56{
 57	cmos_lock = 0;
 58}
 59
 60static inline int do_i_have_lock_cmos(void)
 61{
 62	return (cmos_lock >> 8) == (smp_processor_id() + 1);
 63}
 64
 65static 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)
 95unsigned char rtc_cmos_read(unsigned char addr);
 96void rtc_cmos_write(unsigned char val, unsigned char addr);
 97
 98extern int mach_set_cmos_time(const struct timespec64 *now);
 99extern void mach_get_cmos_time(struct timespec64 *now);
100
101#define RTC_IRQ 8
102
103#endif /* _ASM_X86_MC146818RTC_H */