1 files changed, 103 insertions, 0 deletions
diff --git a/arch/x86/include/asm/mc146818rtc.h b/arch/x86/include/asm/mc146818rtc.h
new file mode 100644
index 000000000..97198001e
--- /dev/null
+++ b/arch/x86/include/asm/mc146818rtc.h
@@ -0,0 +1,103 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Machine dependent access functions for RTC registers.
+ */
+#ifndef _ASM_X86_MC146818RTC_H
+#define _ASM_X86_MC146818RTC_H
+
+#include <asm/io.h>
+#include <asm/processor.h>
+
+#ifndef RTC_PORT
+#define RTC_PORT(x)	(0x70 + (x))
+#define RTC_ALWAYS_BCD	1	/* RTC operates in binary mode */
+#endif
+
+#if defined(CONFIG_X86_32)
+/*
+ * This lock provides nmi access to the CMOS/RTC registers.  It has some
+ * special properties.  It is owned by a CPU and stores the index register
+ * currently being accessed (if owned).  The idea here is that it works
+ * like a normal lock (normally).  However, in an NMI, the NMI code will
+ * first check to see if its CPU owns the lock, meaning that the NMI
+ * interrupted during the read/write of the device.  If it does, it goes ahead
+ * and performs the access and then restores the index register.  If it does
+ * not, it locks normally.
+ *
+ * Note that since we are working with NMIs, we need this lock even in
+ * a non-SMP machine just to mark that the lock is owned.
+ *
+ * This only works with compare-and-swap.  There is no other way to
+ * atomically claim the lock and set the owner.
+ */
+#include <linux/smp.h>
+extern volatile unsigned long cmos_lock;
+
+/*
+ * All of these below must be called with interrupts off, preempt
+ * disabled, etc.
+ */
+
+static inline void lock_cmos(unsigned char reg)
+{
+	unsigned long new;
+	new = ((smp_processor_id() + 1) << 8) | reg;
+	for (;;) {
+		if (cmos_lock) {
+			cpu_relax();
+			continue;
+		}
+		if (__cmpxchg(&cmos_lock, 0, new, sizeof(cmos_lock)) == 0)
+			return;
+	}
+}
+
+static inline void unlock_cmos(void)
+{
+	cmos_lock = 0;
+}
+
+static inline int do_i_have_lock_cmos(void)
+{
+	return (cmos_lock >> 8) == (smp_processor_id() + 1);
+}
+
+static inline unsigned char current_lock_cmos_reg(void)
+{
+	return cmos_lock & 0xff;
+}
+
+#define lock_cmos_prefix(reg)			\
+	do {					\
+		unsigned long cmos_flags;	\
+		local_irq_save(cmos_flags);	\
+		lock_cmos(reg)
+
+#define lock_cmos_suffix(reg)			\
+	unlock_cmos();				\
+	local_irq_restore(cmos_flags);		\
+	} while (0)
+#else
+#define lock_cmos_prefix(reg) do {} while (0)
+#define lock_cmos_suffix(reg) do {} while (0)
+#define lock_cmos(reg) do { } while (0)
+#define unlock_cmos() do { } while (0)
+#define do_i_have_lock_cmos() 0
+#define current_lock_cmos_reg() 0
+#endif
+
+/*
+ * The yet supported machines all access the RTC index register via
+ * an ISA port access but the way to access the date register differs ...
+ */
+#define CMOS_READ(addr) rtc_cmos_read(addr)
+#define CMOS_WRITE(val, addr) rtc_cmos_write(val, addr)
+unsigned char rtc_cmos_read(unsigned char addr);
+void rtc_cmos_write(unsigned char val, unsigned char addr);
+
+extern int mach_set_rtc_mmss(const struct timespec64 *now);
+extern void mach_get_cmos_time(struct timespec64 *now);
+
+#define RTC_IRQ 8
+
+#endif /* _ASM_X86_MC146818RTC_H */