clocksource/drivers: Add a goldfish-timer clocksource

Add a clocksource based on the goldfish-rtc device.

Signed-off-by: Laurent Vivier <laurent@vivier.eu>

drivers/clocksource/Kconfig

@@ -711,4 +711,11 @@ config MICROCHIP_PIT64B
 	  modes and high resolution. It is used as a clocksource
 	  and a clockevent.
 
+config GOLDFISH_TIMER
+	bool "Clocksource using goldfish-rtc"
+	select RTC_CLASS
+	select RTC_DRV_GOLDFISH
+	help
+	  Support for the timer/counter of goldfish-rtc
+
 endmenu

drivers/clocksource/Makefile

@@ -88,3 +88,4 @@ obj-$(CONFIG_CSKY_MP_TIMER)		+= timer-mp-csky.o
 obj-$(CONFIG_GX6605S_TIMER)		+= timer-gx6605s.o
 obj-$(CONFIG_HYPERV_TIMER)		+= hyperv_timer.o
 obj-$(CONFIG_MICROCHIP_PIT64B)		+= timer-microchip-pit64b.o
+obj-$(CONFIG_GOLDFISH_TIMER)		+= timer-goldfish.o

drivers/clocksource/timer-goldfish.c

@@ -0,0 +1,130 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/interrupt.h>
+#include <linux/ioport.h>
+#include <linux/clocksource.h>
+#include <linux/clockchips.h>
+#include <linux/module.h>
+#include <clocksource/timer-goldfish.h>
+
+#define TIMER_TIME_LOW		0x00	/* get low bits of current time  */
+					/*   and update TIMER_TIME_HIGH  */
+#define TIMER_TIME_HIGH		0x04	/* get high bits of time at last */
+					/*   TIMER_TIME_LOW read         */
+#define TIMER_ALARM_LOW		0x08	/* set low bits of alarm and     */
+					/*   activate it                 */
+#define TIMER_ALARM_HIGH	0x0c	/* set high bits of next alarm   */
+#define TIMER_IRQ_ENABLED	0x10
+#define TIMER_CLEAR_ALARM	0x14
+#define TIMER_ALARM_STATUS	0x18
+#define TIMER_CLEAR_INTERRUPT	0x1c
+
+struct goldfish_timer {
+	struct clock_event_device ced;
+	struct resource res;
+	void __iomem *base;
+	int irq;
+};
+
+static struct goldfish_timer *ced_to_gf(struct clock_event_device *ced)
+{
+	return container_of(ced, struct goldfish_timer, ced);
+}
+
+static int goldfish_timer_set_oneshot(struct clock_event_device *evt)
+{
+	struct goldfish_timer *timerdrv = ced_to_gf(evt);
+	void __iomem *base = timerdrv->base;
+
+	__raw_writel(0, base + TIMER_ALARM_HIGH);
+	__raw_writel(0, base + TIMER_ALARM_LOW);
+	__raw_writel(1, base + TIMER_IRQ_ENABLED);
+
+	return 0;
+}
+
+static int goldfish_timer_shutdown(struct clock_event_device *evt)
+{
+	struct goldfish_timer *timerdrv = ced_to_gf(evt);
+	void __iomem *base = timerdrv->base;
+
+	__raw_writel(0, base + TIMER_IRQ_ENABLED);
+
+	return 0;
+}
+
+static int goldfish_timer_next_event(unsigned long delta,
+				     struct clock_event_device *evt)
+{
+	struct goldfish_timer *timerdrv = ced_to_gf(evt);
+	void __iomem *base = timerdrv->base;
+	u64 now;
+
+	__raw_writel(1, base + TIMER_CLEAR_INTERRUPT);
+
+	/*
+	 * time_low: get low bits of current time and update time_high
+	 * time_high: get high bits of time at last time_low read
+	 */
+	now = __raw_readl(base + TIMER_TIME_LOW);
+	now += (u64)__raw_readl(base + TIMER_TIME_HIGH) << 32;
+
+	now += delta;
+
+	__raw_writel(upper_32_bits(now), base + TIMER_ALARM_HIGH);
+	__raw_writel(lower_32_bits(now), base + TIMER_ALARM_LOW);
+
+	return 0;
+}
+
+static irqreturn_t golfish_timer_tick(int irq, void *dev_id)
+{
+	struct clock_event_device *evt = dev_id;
+
+	evt->event_handler(evt);
+
+	return IRQ_HANDLED;
+}
+
+void __init goldfish_timer_init(int irq, void __iomem *base)
+{
+	struct goldfish_timer *timerdrv;
+	int ret;
+
+	timerdrv = kzalloc(sizeof(*timerdrv), GFP_KERNEL);
+	if (!timerdrv)
+		return;
+
+	timerdrv->base = base;
+	timerdrv->irq = irq;
+
+	timerdrv->ced = (struct clock_event_device){
+		.name			= "goldfish_timer",
+		.features		= CLOCK_EVT_FEAT_ONESHOT,
+		.set_state_shutdown	= goldfish_timer_shutdown,
+		.set_state_oneshot      = goldfish_timer_set_oneshot,
+		.set_next_event		= goldfish_timer_next_event,
+		.shift			= 32,
+	};
+	timerdrv->res = (struct resource){
+		.name  = "goldfish_timer",
+		.start = (unsigned long)base,
+		.end   = (unsigned long)base + 0xfff,
+	};
+
+	if (request_resource(&iomem_resource, &timerdrv->res)) {
+		pr_err("Cannot allocate goldfish-timer resource\n");
+		return;
+	}
+
+	ret = request_irq(timerdrv->irq, golfish_timer_tick, IRQF_TIMER,
+			  "goldfish_timer", &timerdrv->ced);
+	if (ret) {
+		pr_err("Couldn't register goldfish-timer interrupt\n");
+		return;
+	}
+
+	clockevents_config_and_register(&timerdrv->ced, NSEC_PER_SEC,
+					1, 0xffffffff);
+}
+EXPORT_SYMBOL_GPL(goldfish_timer_init);

include/clocksource/timer-goldfish.h

@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * goldfish-timer clocksource
+ */
+
+#ifndef _CLOCKSOURCE_GOLDFISH_TIMER_H
+#define _CLOCKSOURCE_GOLDFISH_TIMER_H
+
+extern void goldfish_timer_init(int irq, void __iomem *base);
+
+#endif /* _CLOCKSOURCE_GOLDFISH_TIMER_H */
+