[PATCH v4 2/2] driver: clocksource: Add nxp system counter timer driver support

[Jacky Bai]

From: Bai Ping <ping.bai@xxxxxxx>

The system counter (sys_ctr) is a programmable system counter
which provides a shared time base to the Cortex A15, A7, A53 etc cores.
It is intended for use in applications where the counter is always
powered on and supports multiple, unrelated clocks. The sys_ctr hardware
supports:
 - 56-bit counter width (roll-over time greater than 40 years)
 - compare frame(64-bit compare value) contains programmable interrupt
   generation when compare value <= counter value.

Signed-off-by: Bai Ping <ping.bai@xxxxxxx>
---
change v1->v2:
 - no change 
change v2->v3:
 - remove the clocksource, we only need to use this module for timer purpose,
   so register it as clockevent is enough.
 - use the timer_of_init to init the irq, clock, etc.
 - remove some unnecessary comments.
change v3->v4:
 - use cached value for CMPCR,
 - remove unnecessary timer enabe from set_state_oneshot function.
---
 drivers/clocksource/Kconfig            |   7 ++
 drivers/clocksource/Makefile           |   1 +
 drivers/clocksource/timer-imx-sysctr.c | 146 +++++++++++++++++++++++++
 3 files changed, 154 insertions(+)
 create mode 100644 drivers/clocksource/timer-imx-sysctr.c

diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 6bcaa4e2e72c..ee48620a4561 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -616,6 +616,13 @@ config CLKSRC_IMX_TPM
 	  Enable this option to use IMX Timer/PWM Module (TPM) timer as
 	  clocksource.
 
+config TIMER_IMX_SYS_CTR
+	bool "i.MX system counter timer" if COMPILE_TEST
+	depends on ARCH_MXC
+	select TIMER_OF
+	help
+	  Enable this option to use i.MX system counter timer for clockevent.
+
 config CLKSRC_ST_LPC
 	bool "Low power clocksource found in the LPC" if COMPILE_TEST
 	select TIMER_OF if OF
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index 236858fa7fbf..5fba39e81a40 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -74,6 +74,7 @@ obj-$(CONFIG_CLKSRC_MIPS_GIC)		+= mips-gic-timer.o
 obj-$(CONFIG_CLKSRC_TANGO_XTAL)		+= timer-tango-xtal.o
 obj-$(CONFIG_CLKSRC_IMX_GPT)		+= timer-imx-gpt.o
 obj-$(CONFIG_CLKSRC_IMX_TPM)		+= timer-imx-tpm.o
+obj-$(CONFIG_TIMER_IMX_SYS_CTR)		+= timer-imx-sysctr.o
 obj-$(CONFIG_ASM9260_TIMER)		+= asm9260_timer.o
 obj-$(CONFIG_H8300_TMR8)		+= h8300_timer8.o
 obj-$(CONFIG_H8300_TMR16)		+= h8300_timer16.o
diff --git a/drivers/clocksource/timer-imx-sysctr.c b/drivers/clocksource/timer-imx-sysctr.c
new file mode 100644
index 000000000000..d0428d3189f8
--- /dev/null
+++ b/drivers/clocksource/timer-imx-sysctr.c
@@ -0,0 +1,146 @@
+// SPDX-License-Identifier: GPL-2.0+
+//
+// Copyright 2017-2019 NXP
+
+#include <linux/interrupt.h>
+#include <linux/clockchips.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+
+#include "timer-of.h"
+
+#define CMP_OFFSET	0x10000
+
+#define CNTCV_LO	0x8
+#define CNTCV_HI	0xc
+#define CMPCV_LO	(CMP_OFFSET + 0x20)
+#define CMPCV_HI	(CMP_OFFSET + 0x24)
+#define CMPCR		(CMP_OFFSET + 0x2c)
+
+#define SYS_CTR_EN		0x1
+#define SYS_CTR_IRQ_MASK	0x2
+
+static void __iomem *sys_ctr_base;
+static u32 cmpcr;
+
+static void sysctr_timer_enable(bool enable)
+{
+	cmpcr &= ~SYS_CTR_EN;
+	if (enable)
+		cmpcr |= SYS_CTR_EN;
+
+	writel(cmpcr, sys_ctr_base + CMPCR);
+}
+
+static void sysctr_irq_acknowledge(void)
+{
+	/*
+	 * clear the enable bit(EN =0) will clear
+	 * the status bit(ISTAT = 0), then the interrupt
+	 * signal will be negated(acknowledged).
+	 */
+	sysctr_timer_enable(false);
+}
+
+static inline u64 sysctr_read_counter(void)
+{
+	u32 cnt_hi, tmp_hi, cnt_lo;
+
+	do {
+		cnt_hi = readl_relaxed(sys_ctr_base + CNTCV_HI);
+		cnt_lo = readl_relaxed(sys_ctr_base + CNTCV_LO);
+		tmp_hi = readl_relaxed(sys_ctr_base + CNTCV_HI);
+	} while (tmp_hi != cnt_hi);
+
+	return  ((u64) cnt_hi << 32) | cnt_lo;
+}
+
+static int sysctr_set_next_event(unsigned long delta,
+				 struct clock_event_device *evt)
+{
+	u32 cmp_hi, cmp_lo;
+	u64 next;
+
+	sysctr_timer_enable(false);
+
+	next = sysctr_read_counter();
+
+	next += delta;
+
+	cmp_hi = (next >> 32) & 0x00fffff;
+	cmp_lo = next & 0xffffffff;
+
+	writel_relaxed(cmp_hi, sys_ctr_base + CMPCV_HI);
+	writel_relaxed(cmp_lo, sys_ctr_base + CMPCV_LO);
+
+	sysctr_timer_enable(true);
+
+	return 0;
+}
+
+static int sysctr_set_state_oneshot(struct clock_event_device *evt)
+{
+	return 0;
+}
+
+static int sysctr_set_state_shutdown(struct clock_event_device *evt)
+{
+	sysctr_timer_enable(false);
+
+	return 0;
+}
+
+static irqreturn_t sysctr_timer_interrupt(int irq, void *dev_id)
+{
+	struct clock_event_device *evt = dev_id;
+
+	sysctr_irq_acknowledge();
+
+	evt->event_handler(evt);
+
+	return IRQ_HANDLED;
+}
+
+static struct timer_of to_sysctr = {
+	.flags = TIMER_OF_IRQ | TIMER_OF_CLOCK | TIMER_OF_BASE,
+	.clkevt = {
+		.name			= "i.MX system counter timer",
+		.features		= CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_DYNIRQ,
+		.set_state_oneshot	= sysctr_set_state_oneshot,
+		.set_next_event		= sysctr_set_next_event,
+		.set_state_shutdown	= sysctr_set_state_shutdown,
+		.rating			= 200,
+	},
+	.of_irq = {
+		.handler		= sysctr_timer_interrupt,
+		.flags			= IRQF_TIMER | IRQF_IRQPOLL,
+	},
+	.of_clk = {
+		.name = "per",
+	},
+};
+
+static void __init sysctr_clockevent_init(void)
+{
+	to_sysctr.clkevt.cpumask = cpumask_of(0);
+
+	clockevents_config_and_register(&to_sysctr.clkevt, timer_of_rate(&to_sysctr),
+					0xff, 0x7fffffff);
+}
+
+static int __init sysctr_timer_init(struct device_node *np)
+{
+	int ret = 0;
+
+	ret = timer_of_init(np, &to_sysctr);
+	if (ret)
+		return ret;
+
+	sys_ctr_base = timer_of_base(&to_sysctr);
+	cmpcr = readl(sys_ctr_base + CMPCR);
+
+	sysctr_clockevent_init();
+
+	return 0;
+}
+TIMER_OF_DECLARE(sysctr_timer, "nxp,sysctr-timer", sysctr_timer_init);
-- 
2.21.0