clocksource: Add clockevent support to NPS400 driver

Till now we used clockevent from generic ARC driver.
This was enough as long as we worked with simple multicore SoC.
When we are working with multithread SoC each HW thread can be
scheduled to receive timer interrupt using timer mask register.
This patch will provide a way to control clock events per HW thread.

The design idea is that for each core there is dedicated register
(TSI) serving all 16 HW threads.
The register is a bitmask with one bit for each HW thread.
When HW thread wants that next expiration of timer interrupt will
hit it then the proper bit should be set in this dedicated register.
When timer expires all HW threads within this core which their bit
is set at the TSI register will be interrupted.

Driver can be used from device tree by:
compatible = "ezchip,nps400-timer0" <-- for clocksource
compatible = "ezchip,nps400-timer1" <-- for clockevent

Note that name convention for timer0/timer1 was taken from legacy
ARC design. This design is our base before adding HW threads.
For backward compatibility we keep "ezchip,nps400-timer" for clocksource

Signed-off-by: Noam Camus <noamca@mellanox.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/timer/ezchip,nps400-timer0.txt

@@ -0,0 +1,17 @@
+NPS Network Processor
+
+Required properties:
+
+- compatible :	should be "ezchip,nps400-timer0"
+
+Clocks required for compatible = "ezchip,nps400-timer0":
+- interrupts : The interrupt of the first timer
+- clocks : Must contain a single entry describing the clock input
+
+Example:
+
+timer {
+	compatible = "ezchip,nps400-timer0";
+	interrupts = <3>;
+	clocks = <&sysclk>;
+};

Documentation/devicetree/bindings/timer/ezchip,nps400-timer1.txt

@@ -2,14 +2,14 @@ NPS Network Processor
 
 Required properties:
 
-- compatible :	should be "ezchip,nps400-timer"
+- compatible :	should be "ezchip,nps400-timer1"
 
-Clocks required for compatible = "ezchip,nps400-timer":
+Clocks required for compatible = "ezchip,nps400-timer1":
 - clocks : Must contain a single entry describing the clock input
 
 Example:
 
 timer {
-	compatible = "ezchip,nps400-timer";
+	compatible = "ezchip,nps400-timer1";
 	clocks = <&sysclk>;
 };

drivers/clocksource/timer-nps.c

@@ -111,3 +111,173 @@ static int __init nps_setup_clocksource(struct device_node *node)
 
 CLOCKSOURCE_OF_DECLARE(ezchip_nps400_clksrc, "ezchip,nps400-timer",
 		       nps_setup_clocksource);
+CLOCKSOURCE_OF_DECLARE(ezchip_nps400_clk_src, "ezchip,nps400-timer1",
+		       nps_setup_clocksource);
+
+#ifdef CONFIG_EZNPS_MTM_EXT
+#include <soc/nps/mtm.h>
+
+/* Timer related Aux registers */
+#define NPS_REG_TIMER0_TSI	0xFFFFF850
+#define NPS_REG_TIMER0_LIMIT	0x23
+#define NPS_REG_TIMER0_CTRL	0x22
+#define NPS_REG_TIMER0_CNT	0x21
+
+/*
+ * Interrupt Enabled (IE) - re-arm the timer
+ * Not Halted (NH) - is cleared when working with JTAG (for debug)
+ */
+#define TIMER0_CTRL_IE		BIT(0)
+#define TIMER0_CTRL_NH		BIT(1)
+
+static unsigned long nps_timer0_freq;
+static unsigned long nps_timer0_irq;
+
+static void nps_clkevent_rm_thread(void)
+{
+	int thread;
+	unsigned int cflags, enabled_threads;
+
+	hw_schd_save(&cflags);
+
+	enabled_threads = read_aux_reg(NPS_REG_TIMER0_TSI);
+
+	/* remove thread from TSI1 */
+	thread = read_aux_reg(CTOP_AUX_THREAD_ID);
+	enabled_threads &= ~(1 << thread);
+	write_aux_reg(NPS_REG_TIMER0_TSI, enabled_threads);
+
+	/* Acknowledge and if needed re-arm the timer */
+	if (!enabled_threads)
+		write_aux_reg(NPS_REG_TIMER0_CTRL, TIMER0_CTRL_NH);
+	else
+		write_aux_reg(NPS_REG_TIMER0_CTRL,
+			      TIMER0_CTRL_IE | TIMER0_CTRL_NH);
+
+	hw_schd_restore(cflags);
+}
+
+static void nps_clkevent_add_thread(unsigned long delta)
+{
+	int thread;
+	unsigned int cflags, enabled_threads;
+
+	hw_schd_save(&cflags);
+
+	/* add thread to TSI1 */
+	thread = read_aux_reg(CTOP_AUX_THREAD_ID);
+	enabled_threads = read_aux_reg(NPS_REG_TIMER0_TSI);
+	enabled_threads |= (1 << thread);
+	write_aux_reg(NPS_REG_TIMER0_TSI, enabled_threads);
+
+	/* set next timer event */
+	write_aux_reg(NPS_REG_TIMER0_LIMIT, delta);
+	write_aux_reg(NPS_REG_TIMER0_CNT, 0);
+	write_aux_reg(NPS_REG_TIMER0_CTRL,
+		      TIMER0_CTRL_IE | TIMER0_CTRL_NH);
+
+	hw_schd_restore(cflags);
+}
+
+/*
+ * Whenever anyone tries to change modes, we just mask interrupts
+ * and wait for the next event to get set.
+ */
+static int nps_clkevent_set_state(struct clock_event_device *dev)
+{
+	nps_clkevent_rm_thread();
+	disable_percpu_irq(nps_timer0_irq);
+
+	return 0;
+}
+
+static int nps_clkevent_set_next_event(unsigned long delta,
+				       struct clock_event_device *dev)
+{
+	nps_clkevent_add_thread(delta);
+	enable_percpu_irq(nps_timer0_irq, IRQ_TYPE_NONE);
+
+	return 0;
+}
+
+static DEFINE_PER_CPU(struct clock_event_device, nps_clockevent_device) = {
+	.name				=	"NPS Timer0",
+	.features			=	CLOCK_EVT_FEAT_ONESHOT,
+	.rating				=	300,
+	.set_next_event			=	nps_clkevent_set_next_event,
+	.set_state_oneshot		=	nps_clkevent_set_state,
+	.set_state_oneshot_stopped	=	nps_clkevent_set_state,
+	.set_state_shutdown		=	nps_clkevent_set_state,
+	.tick_resume			=	nps_clkevent_set_state,
+};
+
+static irqreturn_t timer_irq_handler(int irq, void *dev_id)
+{
+	struct clock_event_device *evt = dev_id;
+
+	nps_clkevent_rm_thread();
+	evt->event_handler(evt);
+
+	return IRQ_HANDLED;
+}
+
+static int nps_timer_starting_cpu(unsigned int cpu)
+{
+	struct clock_event_device *evt = this_cpu_ptr(&nps_clockevent_device);
+
+	evt->cpumask = cpumask_of(smp_processor_id());
+
+	clockevents_config_and_register(evt, nps_timer0_freq, 0, ULONG_MAX);
+	enable_percpu_irq(nps_timer0_irq, IRQ_TYPE_NONE);
+
+	return 0;
+}
+
+static int nps_timer_dying_cpu(unsigned int cpu)
+{
+	disable_percpu_irq(nps_timer0_irq);
+	return 0;
+}
+
+static int __init nps_setup_clockevent(struct device_node *node)
+{
+	struct clk *clk;
+	int ret;
+
+	nps_timer0_irq = irq_of_parse_and_map(node, 0);
+	if (nps_timer0_irq <= 0) {
+		pr_err("clockevent: missing irq");
+		return -EINVAL;
+	}
+
+	ret = nps_get_timer_clk(node, &nps_timer0_freq, &clk);
+	if (ret)
+		return ret;
+
+	/* Needs apriori irq_set_percpu_devid() done in intc map function */
+	ret = request_percpu_irq(nps_timer0_irq, timer_irq_handler,
+				 "Timer0 (per-cpu-tick)",
+				 &nps_clockevent_device);
+	if (ret) {
+		pr_err("Couldn't request irq\n");
+		clk_disable_unprepare(clk);
+		return ret;
+	}
+
+	ret = cpuhp_setup_state(CPUHP_AP_ARC_TIMER_STARTING,
+				"clockevents/nps:starting",
+				nps_timer_starting_cpu,
+				nps_timer_dying_cpu);
+	if (ret) {
+		pr_err("Failed to setup hotplug state");
+		clk_disable_unprepare(clk);
+		free_percpu_irq(nps_timer0_irq, &nps_clockevent_device);
+		return ret;
+	}
+
+	return 0;
+}
+
+CLOCKSOURCE_OF_DECLARE(ezchip_nps400_clk_evt, "ezchip,nps400-timer0",
+		       nps_setup_clockevent);
+#endif /* CONFIG_EZNPS_MTM_EXT */