Date:   Tue,  7 Nov 2017 15:19:51 +0800
From:   Rick Chen <rickchen36@...il.com>
To:     daniel.lezcano@...aro.org, tglx@...utronix.de, robh@...nel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        rick@...estech.com
Cc:     Rick Chen <rickchen36@...il.com>, Greentime Hu <green.hu@...il.com>
Subject: [PATCH v3 1/3] clocksource/drivers/atcpit100: Add andestech atcpit100 timer

ATCPIT100 is often used on the Andes architecture,
This timer provide 4 PIT channels. Each PIT channel is a
multi-function timer, can be configured as 32,16,8 bit timers
or PWM as well.

For system timer it will set 32-bit timer0 as clock source
and count downwards until underflow and restart again.

It also set 32-bit timer1 as clock event and count downwards
until condition match. It will generate an interrupt for
handling periodically.

Signed-off-by: Rick Chen <rickchen36@...il.com>
Signed-off-by: Greentime Hu <green.hu@...il.com>
---
 drivers/clocksource/timer-atcpit100.c | 199 ++++++++++++++++++++++++++++++++++
 1 file changed, 199 insertions(+)
 create mode 100644 drivers/clocksource/timer-atcpit100.c

diff --git a/drivers/clocksource/timer-atcpit100.c b/drivers/clocksource/timer-atcpit100.c
new file mode 100644
index 0000000..1a5538b
--- /dev/null
+++ b/drivers/clocksource/timer-atcpit100.c
@@ -0,0 +1,199 @@
+/*
+ *  Andestech ATCPIT100 Timer Device Driver Implementation
+ *
+ *  Copyright (C) 2016 Andes Technology Corporation
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ *
+ */
+#include <linux/irq.h>
+#include <linux/clocksource.h>
+#include <linux/clockchips.h>
+#include <linux/interrupt.h>
+#include <linux/ioport.h>
+#include <linux/cpufreq.h>
+#include <linux/sched.h>
+#include <linux/sched_clock.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+#include <linux/of_platform.h>
+
+void __iomem *base;
+static u32 freq;
+
+/*
+ * Definition of register offsets
+ */
+
+/* ID and Revision Register */
+#define ID_REV		0x0
+
+/* Configuration Register */
+#define CFG		0x10
+
+/* Interrupt Enable Register */
+#define INT_EN		0x14
+#define CH_INT_EN(c, i)	((1<<i)<<(4*c))
+
+/* Interrupt Status Register */
+#define INT_STA		0x18
+#define CH_INT_STA(c, i)	((1<<i)<<(4*c))
+
+/* Channel Enable Register */
+#define CH_EN		0x1C
+#define CH_TMR_EN(c, t)	((1<<t)<<(4*c))
+
+/* Ch n Control REgister */
+#define CH_CTL(n)	(0x20+0x10*n)
+/* Channel clock source , bit 3 , 0:External clock , 1:APB clock */
+#define APB_CLK		(1<<3)
+/* Channel mode , bit 0~2 */
+#define TMR_32		1
+#define TMR_16		2
+#define TMR_8		3
+#define PWM		4
+
+#define CH_REL(n)	(0x24+0x10*n)
+#define CH_CNT(n)	(0x28+0x10*n)
+
+static unsigned long atcpit100_read_current_timer_down(void)
+{
+	return ~readl(base + CH_CNT(1));
+}
+
+static u64 notrace atcpit100_read_sched_clock_down(void)
+{
+	return atcpit100_read_current_timer_down();
+}
+
+static void atcpit100_clocksource_init(void)
+{
+	writel(0xffffffff, base + CH_REL(1));
+	writel(APB_CLK|TMR_32, base + CH_CTL(1));
+	writel(readl(base + CH_EN) | CH_TMR_EN(1, 0), base + CH_EN);
+	clocksource_mmio_init(base + CH_CNT(1),
+			      "atcpit100_tm1",
+			      freq,
+			      300, 32, clocksource_mmio_readl_down);
+	sched_clock_register(atcpit100_read_sched_clock_down, 32, freq);
+}
+
+static int atcpit100_set_next_event(unsigned long cycles,
+		struct clock_event_device *evt)
+{
+	writel(cycles, base + CH_REL(0));
+
+	return 0;
+}
+
+static int atcpit100_set_state_shutdown(struct clock_event_device *evt)
+{
+	writel(readl(base + CH_EN) & ~CH_TMR_EN(0, 0), base + CH_EN);
+
+	return 0;
+}
+static int atcpit100_set_state_periodic(struct clock_event_device *evt)
+{
+	writel(freq / HZ - 1, base + CH_CNT(0));
+	writel(freq / HZ - 1, base + CH_REL(0));
+	writel(readl(base + CH_EN) | CH_TMR_EN(0, 0), base + CH_EN);
+
+	return 0;
+}
+static int atcpit100_tick_resume(struct clock_event_device *evt)
+{
+	writel(readl(base + INT_STA) | CH_INT_STA(0, 0), base + INT_STA);
+	writel(readl(base + CH_EN) | CH_TMR_EN(0, 0), base + CH_EN);
+
+	return 0;
+}
+static int atcpit100_set_state_oneshot(struct clock_event_device *evt)
+{
+	writel(0xffffffff, base + CH_REL(0));
+	writel(readl(base + CH_EN) | CH_TMR_EN(0, 0), base + CH_EN);
+
+	return 0;
+}
+
+static struct clock_event_device clockevent_atcpit100 = {
+	.name		= "atcpit100_tm0",
+	.features       = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_PERIODIC,
+	.shift		= 32,
+	.cpumask	= cpu_all_mask,
+	.set_next_event	= atcpit100_set_next_event,
+	.set_state_shutdown = atcpit100_set_state_shutdown,
+	.set_state_periodic = atcpit100_set_state_periodic,
+	.set_state_oneshot = atcpit100_set_state_oneshot,
+	.tick_resume = atcpit100_tick_resume,
+};
+
+static irqreturn_t timer1_interrupt(int irq, void *dev_id)
+{
+	struct clock_event_device *evt = dev_id;
+
+	writel(readl(base + INT_STA) | CH_INT_STA(0, 0), base + INT_STA);
+
+	evt->event_handler(evt);
+
+	return IRQ_HANDLED;
+}
+
+static struct irqaction timer1_irq = {
+	.name		= "Timer Tick",
+	.flags		= IRQF_TIMER | IRQF_IRQPOLL,
+	.handler	= timer1_interrupt,
+	.dev_id		= &clockevent_atcpit100
+};
+
+static void __init atcpit100_clockevent_init(int irq)
+{
+	struct clock_event_device *evt = &clockevent_atcpit100;
+
+	evt->mult = div_sc(freq, NSEC_PER_SEC, evt->shift);
+	evt->max_delta_ns = clockevent_delta2ns(0xffffffff, evt);
+	evt->min_delta_ns = clockevent_delta2ns(3, evt);
+	clockevents_register_device(evt);
+	setup_irq(irq, &timer1_irq);
+}
+
+static int __init atcpit100_init(struct device_node *dev)
+{
+	int irq;
+
+	base = of_iomap(dev, 0);
+	if (!base) {
+		pr_warn("Can't remap registers");
+		return -ENXIO;
+	}
+
+	if (of_property_read_u32(dev, "clock-frequency", &freq)) {
+		pr_warn("Can't read clock-frequency");
+		return -EINVAL;
+	}
+	irq = irq_of_parse_and_map(dev, 0);
+
+	if (irq <= 0) {
+		pr_warn("Failed to map timer IRQ\n");
+		return -EINVAL;
+	}
+	pr_info("ATCPIT100 timer 1 installed on IRQ %d, with clock %d at %d HZ. in %p\n",
+			irq, freq, HZ, base);
+	writel(APB_CLK|TMR_32, base + CH_CTL(0));
+	writel(readl(base + INT_EN) | CH_INT_EN(0, 0), base + INT_EN);
+	writel(readl(base + CH_EN) | CH_TMR_EN(0, 0), base + CH_EN);
+	atcpit100_clocksource_init();
+	atcpit100_clockevent_init(irq);
+
+	return 0;
+}
+
+TIMER_OF_DECLARE(atcpit100, "andestech,atcpit100", atcpit100_init);
-- 
2.7.4

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