hw/rtc.c

#include "kvm/rtc.h"

#include "kvm/fdt.h"
#include "kvm/ioport.h"
#include "kvm/kvm.h"

#include <time.h>

#if defined(CONFIG_ARM) || defined(CONFIG_ARM64)
#define RTC_BUS_TYPE		DEVICE_BUS_MMIO
#define RTC_BASE_ADDRESS	ARM_RTC_MMIO_BASE
#elif defined(CONFIG_RISCV)
#define RTC_BUS_TYPE		DEVICE_BUS_MMIO
#define RTC_BASE_ADDRESS	RISCV_RTC_MMIO_BASE
#else
/* PORT 0070-007F - CMOS RAM/RTC (REAL TIME CLOCK) */
#define RTC_BUS_TYPE		DEVICE_BUS_IOPORT
#define RTC_BASE_ADDRESS	0x70
#endif

/*
 * MC146818 RTC registers
 */
#define RTC_SECONDS			0x00
#define RTC_SECONDS_ALARM		0x01
#define RTC_MINUTES			0x02
#define RTC_MINUTES_ALARM		0x03
#define RTC_HOURS			0x04
#define RTC_HOURS_ALARM			0x05
#define RTC_DAY_OF_WEEK			0x06
#define RTC_DAY_OF_MONTH		0x07
#define RTC_MONTH			0x08
#define RTC_YEAR			0x09
#define RTC_CENTURY			0x32

#define RTC_REG_A			0x0A
#define RTC_REG_B			0x0B
#define RTC_REG_C			0x0C
#define RTC_REG_D			0x0D

/*
 * Register D Bits
 */
#define RTC_REG_D_VRT			(1 << 7)

struct rtc_device {
	u8			cmos_idx;
	u8			cmos_data[128];
};

static struct rtc_device	rtc;

static inline unsigned char bin2bcd(unsigned val)
{
	return ((val / 10) << 4) + val % 10;
}

static void cmos_ram_io(struct kvm_cpu *vcpu, u64 addr, u8 *data,
			u32 len, u8 is_write, void *ptr)
{
	struct tm *tm;
	time_t ti;

	if (is_write) {
		if (addr == RTC_BASE_ADDRESS) {	/* index register */
			u8 value = ioport__read8(data);

			vcpu->kvm->nmi_disabled	= value & (1UL << 7);
			rtc.cmos_idx		= value & ~(1UL << 7);

			return;
		}

		switch (rtc.cmos_idx) {
		case RTC_REG_C:
		case RTC_REG_D:
			/* Read-only */
			break;
		default:
			rtc.cmos_data[rtc.cmos_idx] = ioport__read8(data);
			break;
		}
		return;
	}

	if (addr == RTC_BASE_ADDRESS)	/* index register is write-only */
		return;

	time(&ti);

	tm = gmtime(&ti);

	switch (rtc.cmos_idx) {
	case RTC_SECONDS:
		ioport__write8(data, bin2bcd(tm->tm_sec));
		break;
	case RTC_MINUTES:
		ioport__write8(data, bin2bcd(tm->tm_min));
		break;
	case RTC_HOURS:
		ioport__write8(data, bin2bcd(tm->tm_hour));
		break;
	case RTC_DAY_OF_WEEK:
		ioport__write8(data, bin2bcd(tm->tm_wday + 1));
		break;
	case RTC_DAY_OF_MONTH:
		ioport__write8(data, bin2bcd(tm->tm_mday));
		break;
	case RTC_MONTH:
		ioport__write8(data, bin2bcd(tm->tm_mon + 1));
		break;
	case RTC_YEAR: {
		int year;

		year = tm->tm_year + 1900;

		ioport__write8(data, bin2bcd(year % 100));

		break;
	}
	case RTC_CENTURY: {
		int year;

		year = tm->tm_year + 1900;

		ioport__write8(data, bin2bcd(year / 100));

		break;
	}
	default:
		ioport__write8(data, rtc.cmos_data[rtc.cmos_idx]);
		break;
	}
}

#ifdef CONFIG_HAS_LIBFDT
static void generate_rtc_fdt_node(void *fdt,
				  struct device_header *dev_hdr,
				  void (*generate_irq_prop)(void *fdt,
							    u8 irq,
							    enum irq_type))
{
	u64 reg_prop[2] = { cpu_to_fdt64(RTC_BASE_ADDRESS), cpu_to_fdt64(2) };

	_FDT(fdt_begin_node(fdt, "rtc"));
	_FDT(fdt_property_string(fdt, "compatible", "motorola,mc146818"));
	_FDT(fdt_property(fdt, "reg", reg_prop, sizeof(reg_prop)));
	_FDT(fdt_end_node(fdt));
}
#else
#define generate_rtc_fdt_node NULL
#endif

struct device_header rtc_dev_hdr = {
	.bus_type = RTC_BUS_TYPE,
	.data = generate_rtc_fdt_node,
};

int rtc__init(struct kvm *kvm)
{
	int r;

	r = device__register(&rtc_dev_hdr);
	if (r < 0)
		return r;

	r = kvm__register_iotrap(kvm, RTC_BASE_ADDRESS, 2, cmos_ram_io, NULL,
				 RTC_BUS_TYPE);
	if (r < 0)
		goto out_device;

	/* Set the VRT bit in Register D to indicate valid RAM and time */
	rtc.cmos_data[RTC_REG_D] = RTC_REG_D_VRT;

	return r;

out_device:
	device__unregister(&rtc_dev_hdr);

	return r;
}
dev_init(rtc__init);

int rtc__exit(struct kvm *kvm)
{
	kvm__deregister_iotrap(kvm, RTC_BASE_ADDRESS, RTC_BUS_TYPE);

	return 0;
}
dev_exit(rtc__exit);