clocksource: import ARC timer driver

This adds support for

 - CONFIG_ARC_TIMERS : legacy 32-bit TIMER0 and TIMER1 which count UP
   from @CNT to @LIMIT, before optionally triggering an interrupt.
   These are programmed using ARC auxiliary register interface.
   These are present in all ARC cores (ARC700 and ARC HS38)
   TIMER0 serves as clockevent for all ARC linux builds.
   TIMER1 is used for clocksource in arc700 builds.

 - CONFIG_ARC_TIMERS_64BIT: 64-bit counters, RTC and GFRC found in
   ARC HS38 cores. These are independnet IP blocks with different
   programming model respectively.

Link: http://lkml.kernel.org/r/20161111231132.GA4186@mai
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

3 files changed, 357 insertions, 0 deletions

diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index e2c6e43..4866f7a 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -282,6 +282,26 @@ config CLKSRC_MPS2
 	select CLKSRC_MMIO
 	select CLKSRC_OF
 
+config ARC_TIMERS
+	bool "Support for 32-bit TIMERn counters in ARC Cores" if COMPILE_TEST
+	depends on GENERIC_CLOCKEVENTS
+	select CLKSRC_OF
+	help
+	  These are legacy 32-bit TIMER0 and TIMER1 counters found on all ARC cores
+	  (ARC700 as well as ARC HS38).
+	  TIMER0 serves as clockevent while TIMER1 provides clocksource
+
+config ARC_TIMERS_64BIT
+	bool "Support for 64-bit counters in ARC HS38 cores" if COMPILE_TEST
+	depends on GENERIC_CLOCKEVENTS
+	depends on ARC_TIMERS
+	select CLKSRC_OF
+	help
+	  This enables 2 different 64-bit timers: RTC (for UP) and GFRC (for SMP)
+	  RTC is implemented inside the core, while GFRC sits outside the core in
+	  ARConnect IP block. Driver automatically picks one of them for clocksource
+	  as appropriate.
+
 config ARM_ARCH_TIMER
 	bool
 	select CLKSRC_OF if OF
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index cf87f40..a14111e 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -51,6 +51,7 @@ obj-$(CONFIG_CLKSRC_TI_32K)	+= timer-ti-32k.o
 obj-$(CONFIG_CLKSRC_NPS)	+= timer-nps.o
 obj-$(CONFIG_OXNAS_RPS_TIMER)	+= timer-oxnas-rps.o
 
+obj-$(CONFIG_ARC_TIMERS)		+= arc_timer.o
 obj-$(CONFIG_ARM_ARCH_TIMER)		+= arm_arch_timer.o
 obj-$(CONFIG_ARM_GLOBAL_TIMER)		+= arm_global_timer.o
 obj-$(CONFIG_ARMV7M_SYSTICK)		+= armv7m_systick.o
diff --git a/drivers/clocksource/arc_timer.c b/drivers/clocksource/arc_timer.c
new file mode 100644
index 0000000..a49748d
--- /dev/null
+++ b/drivers/clocksource/arc_timer.c
@@ -0,0 +1,336 @@
+/*
+ * Copyright (C) 2016-17 Synopsys, Inc. (www.synopsys.com)
+ * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+/* ARC700 has two 32bit independent prog Timers: TIMER0 and TIMER1, Each can be
+ * programmed to go from @count to @limit and optionally interrupt.
+ * We've designated TIMER0 for clockevents and TIMER1 for clocksource
+ *
+ * ARCv2 based HS38 cores have RTC (in-core) and GFRC (inside ARConnect/MCIP)
+ * which are suitable for UP and SMP based clocksources respectively
+ */
+
+#include <linux/interrupt.h>
+#include <linux/clk.h>
+#include <linux/clk-provider.h>
+#include <linux/clocksource.h>
+#include <linux/clockchips.h>
+#include <linux/cpu.h>
+#include <linux/of.h>
+#include <linux/of_irq.h>
+
+#include <soc/arc/timers.h>
+#include <soc/arc/mcip.h>
+
+
+static unsigned long arc_timer_freq;
+
+static int noinline arc_get_timer_clk(struct device_node *node)
+{
+	struct clk *clk;
+	int ret;
+
+	clk = of_clk_get(node, 0);
+	if (IS_ERR(clk)) {
+		pr_err("timer missing clk");
+		return PTR_ERR(clk);
+	}
+
+	ret = clk_prepare_enable(clk);
+	if (ret) {
+		pr_err("Couldn't enable parent clk\n");
+		return ret;
+	}
+
+	arc_timer_freq = clk_get_rate(clk);
+
+	return 0;
+}
+
+/********** Clock Source Device *********/
+
+#ifdef CONFIG_ARC_TIMERS_64BIT
+
+static cycle_t arc_read_gfrc(struct clocksource *cs)
+{
+	unsigned long flags;
+	u32 l, h;
+
+	local_irq_save(flags);
+
+	__mcip_cmd(CMD_GFRC_READ_LO, 0);
+	l = read_aux_reg(ARC_REG_MCIP_READBACK);
+
+	__mcip_cmd(CMD_GFRC_READ_HI, 0);
+	h = read_aux_reg(ARC_REG_MCIP_READBACK);
+
+	local_irq_restore(flags);
+
+	return (((cycle_t)h) << 32) | l;
+}
+
+static struct clocksource arc_counter_gfrc = {
+	.name   = "ARConnect GFRC",
+	.rating = 400,
+	.read   = arc_read_gfrc,
+	.mask   = CLOCKSOURCE_MASK(64),
+	.flags  = CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+static int __init arc_cs_setup_gfrc(struct device_node *node)
+{
+	struct mcip_bcr mp;
+	int ret;
+
+	READ_BCR(ARC_REG_MCIP_BCR, mp);
+	if (!mp.gfrc) {
+		pr_warn("Global-64-bit-Ctr clocksource not detected");
+		return -ENXIO;
+	}
+
+	ret = arc_get_timer_clk(node);
+	if (ret)
+		return ret;
+
+	return clocksource_register_hz(&arc_counter_gfrc, arc_timer_freq);
+}
+CLOCKSOURCE_OF_DECLARE(arc_gfrc, "snps,archs-timer-gfrc", arc_cs_setup_gfrc);
+
+#define AUX_RTC_CTRL	0x103
+#define AUX_RTC_LOW	0x104
+#define AUX_RTC_HIGH	0x105
+
+static cycle_t arc_read_rtc(struct clocksource *cs)
+{
+	unsigned long status;
+	u32 l, h;
+
+	/*
+	 * hardware has an internal state machine which tracks readout of
+	 * low/high and updates the CTRL.status if
+	 *  - interrupt/exception taken between the two reads
+	 *  - high increments after low has been read
+	 */
+	do {
+		l = read_aux_reg(AUX_RTC_LOW);
+		h = read_aux_reg(AUX_RTC_HIGH);
+		status = read_aux_reg(AUX_RTC_CTRL);
+	} while (!(status & _BITUL(31)));
+
+	return (((cycle_t)h) << 32) | l;
+}
+
+static struct clocksource arc_counter_rtc = {
+	.name   = "ARCv2 RTC",
+	.rating = 350,
+	.read   = arc_read_rtc,
+	.mask   = CLOCKSOURCE_MASK(64),
+	.flags  = CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+static int __init arc_cs_setup_rtc(struct device_node *node)
+{
+	struct bcr_timer timer;
+	int ret;
+
+	READ_BCR(ARC_REG_TIMERS_BCR, timer);
+	if (!timer.rtc) {
+		pr_warn("Local-64-bit-Ctr clocksource not detected");
+		return -ENXIO;
+	}
+
+	/* Local to CPU hence not usable in SMP */
+	if (IS_ENABLED(CONFIG_SMP)) {
+		pr_warn("Local-64-bit-Ctr not usable in SMP");
+		return -EINVAL;
+	}
+
+	ret = arc_get_timer_clk(node);
+	if (ret)
+		return ret;
+
+	write_aux_reg(AUX_RTC_CTRL, 1);
+
+	return clocksource_register_hz(&arc_counter_rtc, arc_timer_freq);
+}
+CLOCKSOURCE_OF_DECLARE(arc_rtc, "snps,archs-timer-rtc", arc_cs_setup_rtc);
+
+#endif
+
+/*
+ * 32bit TIMER1 to keep counting monotonically and wraparound
+ */
+
+static cycle_t arc_read_timer1(struct clocksource *cs)
+{
+	return (cycle_t) read_aux_reg(ARC_REG_TIMER1_CNT);
+}
+
+static struct clocksource arc_counter_timer1 = {
+	.name   = "ARC Timer1",
+	.rating = 300,
+	.read   = arc_read_timer1,
+	.mask   = CLOCKSOURCE_MASK(32),
+	.flags  = CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+static int __init arc_cs_setup_timer1(struct device_node *node)
+{
+	int ret;
+
+	/* Local to CPU hence not usable in SMP */
+	if (IS_ENABLED(CONFIG_SMP))
+		return -EINVAL;
+
+	ret = arc_get_timer_clk(node);
+	if (ret)
+		return ret;
+
+	write_aux_reg(ARC_REG_TIMER1_LIMIT, ARC_TIMERN_MAX);
+	write_aux_reg(ARC_REG_TIMER1_CNT, 0);
+	write_aux_reg(ARC_REG_TIMER1_CTRL, TIMER_CTRL_NH);
+
+	return clocksource_register_hz(&arc_counter_timer1, arc_timer_freq);
+}
+
+/********** Clock Event Device *********/
+
+static int arc_timer_irq;
+
+/*
+ * Arm the timer to interrupt after @cycles
+ * The distinction for oneshot/periodic is done in arc_event_timer_ack() below
+ */
+static void arc_timer_event_setup(unsigned int cycles)
+{
+	write_aux_reg(ARC_REG_TIMER0_LIMIT, cycles);
+	write_aux_reg(ARC_REG_TIMER0_CNT, 0);	/* start from 0 */
+
+	write_aux_reg(ARC_REG_TIMER0_CTRL, TIMER_CTRL_IE | TIMER_CTRL_NH);
+}
+
+
+static int arc_clkevent_set_next_event(unsigned long delta,
+				       struct clock_event_device *dev)
+{
+	arc_timer_event_setup(delta);
+	return 0;
+}
+
+static int arc_clkevent_set_periodic(struct clock_event_device *dev)
+{
+	/*
+	 * At X Hz, 1 sec = 1000ms -> X cycles;
+	 *		      10ms -> X / 100 cycles
+	 */
+	arc_timer_event_setup(arc_timer_freq / HZ);
+	return 0;
+}
+
+static DEFINE_PER_CPU(struct clock_event_device, arc_clockevent_device) = {
+	.name			= "ARC Timer0",
+	.features		= CLOCK_EVT_FEAT_ONESHOT |
+				  CLOCK_EVT_FEAT_PERIODIC,
+	.rating			= 300,
+	.set_next_event		= arc_clkevent_set_next_event,
+	.set_state_periodic	= arc_clkevent_set_periodic,
+};
+
+static irqreturn_t timer_irq_handler(int irq, void *dev_id)
+{
+	/*
+	 * Note that generic IRQ core could have passed @evt for @dev_id if
+	 * irq_set_chip_and_handler() asked for handle_percpu_devid_irq()
+	 */
+	struct clock_event_device *evt = this_cpu_ptr(&arc_clockevent_device);
+	int irq_reenable = clockevent_state_periodic(evt);
+
+	/*
+	 * Any write to CTRL reg ACks the interrupt, we rewrite the
+	 * Count when [N]ot [H]alted bit.
+	 * And re-arm it if perioid by [I]nterrupt [E]nable bit
+	 */
+	write_aux_reg(ARC_REG_TIMER0_CTRL, irq_reenable | TIMER_CTRL_NH);
+
+	evt->event_handler(evt);
+
+	return IRQ_HANDLED;
+}
+
+
+static int arc_timer_starting_cpu(unsigned int cpu)
+{
+	struct clock_event_device *evt = this_cpu_ptr(&arc_clockevent_device);
+
+	evt->cpumask = cpumask_of(smp_processor_id());
+
+	clockevents_config_and_register(evt, arc_timer_freq, 0, ARC_TIMERN_MAX);
+	enable_percpu_irq(arc_timer_irq, 0);
+	return 0;
+}
+
+static int arc_timer_dying_cpu(unsigned int cpu)
+{
+	disable_percpu_irq(arc_timer_irq);
+	return 0;
+}
+
+/*
+ * clockevent setup for boot CPU
+ */
+static int __init arc_clockevent_setup(struct device_node *node)
+{
+	struct clock_event_device *evt = this_cpu_ptr(&arc_clockevent_device);
+	int ret;
+
+	arc_timer_irq = irq_of_parse_and_map(node, 0);
+	if (arc_timer_irq <= 0) {
+		pr_err("clockevent: missing irq");
+		return -EINVAL;
+	}
+
+	ret = arc_get_timer_clk(node);
+	if (ret) {
+		pr_err("clockevent: missing clk");
+		return ret;
+	}
+
+	/* Needs apriori irq_set_percpu_devid() done in intc map function */
+	ret = request_percpu_irq(arc_timer_irq, timer_irq_handler,
+				 "Timer0 (per-cpu-tick)", evt);
+	if (ret) {
+		pr_err("clockevent: unable to request irq\n");
+		return ret;
+	}
+
+	ret = cpuhp_setup_state(CPUHP_AP_ARC_TIMER_STARTING,
+				"AP_ARC_TIMER_STARTING",
+				arc_timer_starting_cpu,
+				arc_timer_dying_cpu);
+	if (ret) {
+		pr_err("Failed to setup hotplug state");
+		return ret;
+	}
+	return 0;
+}
+
+static int __init arc_of_timer_init(struct device_node *np)
+{
+	static int init_count = 0;
+	int ret;
+
+	if (!init_count) {
+		init_count = 1;
+		ret = arc_clockevent_setup(np);
+	} else {
+		ret = arc_cs_setup_timer1(np);
+	}
+
+	return ret;
+}
+CLOCKSOURCE_OF_DECLARE(arc_clkevt, "snps,arc-timer", arc_of_timer_init);