hpet.c

// SPDX-License-Identifier: GPL-2.0
#include <linux/init.h>
#include <linux/pci.h>
#include <linux/percpu.h>
#include <linux/delay.h>
#include <linux/spinlock.h>
#include <linux/interrupt.h>

#include <asm/hpet.h>
#include <asm/time.h>

#define SMBUS_CFG_BASE		(loongson_sysconf.ht_control_base + 0x0300a000)
#define SMBUS_PCI_REG40		0x40
#define SMBUS_PCI_REG64		0x64
#define SMBUS_PCI_REGB4		0xb4

#define HPET_MIN_CYCLES		16
#define HPET_MIN_PROG_DELTA	(HPET_MIN_CYCLES * 12)

static DEFINE_SPINLOCK(hpet_lock);
DEFINE_PER_CPU(struct clock_event_device, hpet_clockevent_device);

static unsigned int smbus_read(int offset)
{
	return *(volatile unsigned int *)(SMBUS_CFG_BASE + offset);
}

static void smbus_write(int offset, int data)
{
	*(volatile unsigned int *)(SMBUS_CFG_BASE + offset) = data;
}

static void smbus_enable(int offset, int bit)
{
	unsigned int cfg = smbus_read(offset);

	cfg |= bit;
	smbus_write(offset, cfg);
}

static int hpet_read(int offset)
{
	return *(volatile unsigned int *)(HPET_MMIO_ADDR + offset);
}

static void hpet_write(int offset, int data)
{
	*(volatile unsigned int *)(HPET_MMIO_ADDR + offset) = data;
}

static void hpet_start_counter(void)
{
	unsigned int cfg = hpet_read(HPET_CFG);

	cfg |= HPET_CFG_ENABLE;
	hpet_write(HPET_CFG, cfg);
}

static void hpet_stop_counter(void)
{
	unsigned int cfg = hpet_read(HPET_CFG);

	cfg &= ~HPET_CFG_ENABLE;
	hpet_write(HPET_CFG, cfg);
}

static void hpet_reset_counter(void)
{
	hpet_write(HPET_COUNTER, 0);
	hpet_write(HPET_COUNTER + 4, 0);
}

static void hpet_restart_counter(void)
{
	hpet_stop_counter();
	hpet_reset_counter();
	hpet_start_counter();
}

static void hpet_enable_legacy_int(void)
{
	/* Do nothing on Loongson-3 */
}

static int hpet_set_state_periodic(struct clock_event_device *evt)
{
	int cfg;

	spin_lock(&hpet_lock);

	pr_info("set clock event to periodic mode!\n");
	/* stop counter */
	hpet_stop_counter();

	/* enables the timer0 to generate a periodic interrupt */
	cfg = hpet_read(HPET_T0_CFG);
	cfg &= ~HPET_TN_LEVEL;
	cfg |= HPET_TN_ENABLE | HPET_TN_PERIODIC | HPET_TN_SETVAL |
		HPET_TN_32BIT;
	hpet_write(HPET_T0_CFG, cfg);

	/* set the comparator */
	hpet_write(HPET_T0_CMP, HPET_COMPARE_VAL);
	udelay(1);
	hpet_write(HPET_T0_CMP, HPET_COMPARE_VAL);

	/* start counter */
	hpet_start_counter();

	spin_unlock(&hpet_lock);
	return 0;
}

static int hpet_set_state_shutdown(struct clock_event_device *evt)
{
	int cfg;

	spin_lock(&hpet_lock);

	cfg = hpet_read(HPET_T0_CFG);
	cfg &= ~HPET_TN_ENABLE;
	hpet_write(HPET_T0_CFG, cfg);

	spin_unlock(&hpet_lock);
	return 0;
}

static int hpet_set_state_oneshot(struct clock_event_device *evt)
{
	int cfg;

	spin_lock(&hpet_lock);

	pr_info("set clock event to one shot mode!\n");
	cfg = hpet_read(HPET_T0_CFG);
	/*
	 * set timer0 type
	 * 1 : periodic interrupt
	 * 0 : non-periodic(oneshot) interrupt
	 */
	cfg &= ~HPET_TN_PERIODIC;
	cfg |= HPET_TN_ENABLE | HPET_TN_32BIT;
	hpet_write(HPET_T0_CFG, cfg);

	spin_unlock(&hpet_lock);
	return 0;
}

static int hpet_tick_resume(struct clock_event_device *evt)
{
	spin_lock(&hpet_lock);
	hpet_enable_legacy_int();
	spin_unlock(&hpet_lock);

	return 0;
}

static int hpet_next_event(unsigned long delta,
		struct clock_event_device *evt)
{
	u32 cnt;
	s32 res;

	cnt = hpet_read(HPET_COUNTER);
	cnt += (u32) delta;
	hpet_write(HPET_T0_CMP, cnt);

	res = (s32)(cnt - hpet_read(HPET_COUNTER));

	return res < HPET_MIN_CYCLES ? -ETIME : 0;
}

static irqreturn_t hpet_irq_handler(int irq, void *data)
{
	int is_irq;
	struct clock_event_device *cd;
	unsigned int cpu = smp_processor_id();

	is_irq = hpet_read(HPET_STATUS);
	if (is_irq & HPET_T0_IRS) {
		/* clear the TIMER0 irq status register */
		hpet_write(HPET_STATUS, HPET_T0_IRS);
		cd = &per_cpu(hpet_clockevent_device, cpu);
		cd->event_handler(cd);
		return IRQ_HANDLED;
	}
	return IRQ_NONE;
}

/*
 * hpet address assignation and irq setting should be done in bios.
 * but pmon don't do this, we just setup here directly.
 * The operation under is normal. unfortunately, hpet_setup process
 * is before pci initialize.
 *
 * {
 *	struct pci_dev *pdev;
 *
 *	pdev = pci_get_device(PCI_VENDOR_ID_ATI, PCI_DEVICE_ID_ATI_SBX00_SMBUS, NULL);
 *	pci_write_config_word(pdev, SMBUS_PCI_REGB4, HPET_ADDR);
 *
 *	...
 * }
 */
static void hpet_setup(void)
{
	/* set hpet base address */
	smbus_write(SMBUS_PCI_REGB4, HPET_ADDR);

	/* enable decoding of access to HPET MMIO*/
	smbus_enable(SMBUS_PCI_REG40, (1 << 28));

	/* HPET irq enable */
	smbus_enable(SMBUS_PCI_REG64, (1 << 10));

	hpet_enable_legacy_int();
}

void __init setup_hpet_timer(void)
{
	unsigned long flags = IRQF_NOBALANCING | IRQF_TIMER;
	unsigned int cpu = smp_processor_id();
	struct clock_event_device *cd;

	hpet_setup();

	cd = &per_cpu(hpet_clockevent_device, cpu);
	cd->name = "hpet";
	cd->rating = 100;
	cd->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
	cd->set_state_shutdown = hpet_set_state_shutdown;
	cd->set_state_periodic = hpet_set_state_periodic;
	cd->set_state_oneshot = hpet_set_state_oneshot;
	cd->tick_resume = hpet_tick_resume;
	cd->set_next_event = hpet_next_event;
	cd->irq = HPET_T0_IRQ;
	cd->cpumask = cpumask_of(cpu);
	clockevent_set_clock(cd, HPET_FREQ);
	cd->max_delta_ns = clockevent_delta2ns(0x7fffffff, cd);
	cd->max_delta_ticks = 0x7fffffff;
	cd->min_delta_ns = clockevent_delta2ns(HPET_MIN_PROG_DELTA, cd);
	cd->min_delta_ticks = HPET_MIN_PROG_DELTA;

	clockevents_register_device(cd);
	if (request_irq(HPET_T0_IRQ, hpet_irq_handler, flags, "hpet", NULL))
		pr_err("Failed to request irq %d (hpet)\n", HPET_T0_IRQ);
	pr_info("hpet clock event device register\n");
}

static u64 hpet_read_counter(struct clocksource *cs)
{
	return (u64)hpet_read(HPET_COUNTER);
}

static void hpet_suspend(struct clocksource *cs)
{
}

static void hpet_resume(struct clocksource *cs)
{
	hpet_setup();
	hpet_restart_counter();
}

static struct clocksource csrc_hpet = {
	.name = "hpet",
	/* mips clocksource rating is less than 300, so hpet is better. */
	.rating = 300,
	.read = hpet_read_counter,
	.mask = CLOCKSOURCE_MASK(32),
	/* oneshot mode work normal with this flag */
	.flags = CLOCK_SOURCE_IS_CONTINUOUS,
	.suspend = hpet_suspend,
	.resume = hpet_resume,
	.mult = 0,
	.shift = 10,
};

int __init init_hpet_clocksource(void)
{
	csrc_hpet.mult = clocksource_hz2mult(HPET_FREQ, csrc_hpet.shift);
	return clocksource_register_hz(&csrc_hpet, HPET_FREQ);
}

arch_initcall(init_hpet_clocksource);