ARM: local timers: Add A15 architected timer support

Add support for the A15 generic timer and clocksource.
As the timer generates interrupts on a different PPI depending
on the execution mode (normal or secure), it is possible to
register two different PPIs.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

arch/arm/Kconfig

@@ -1543,6 +1543,12 @@ config HAVE_ARM_SCU
 	help
 	  This option enables support for the ARM system coherency unit
 
+config ARM_ARCH_TIMER
+	bool "Architected timer support"
+	depends on CPU_V7
+	help
+	  This option enables support for the ARM architected timer
+
 config HAVE_ARM_TWD
 	bool
 	depends on SMP

arch/arm/include/asm/arch_timer.h

@@ -0,0 +1,19 @@
+#ifndef __ASMARM_ARCH_TIMER_H
+#define __ASMARM_ARCH_TIMER_H
+
+#include <linux/ioport.h>
+
+struct arch_timer {
+	struct resource	res[2];
+};
+
+#ifdef CONFIG_ARM_ARCH_TIMER
+int arch_timer_register(struct arch_timer *);
+#else
+static inline int arch_timer_register(struct arch_timer *at)
+{
+	return -ENXIO;
+}
+#endif
+
+#endif

arch/arm/kernel/Makefile

@@ -34,6 +34,7 @@ obj-$(CONFIG_ARM_CPU_SUSPEND)	+= sleep.o suspend.o
 obj-$(CONFIG_SMP)		+= smp.o smp_tlb.o
 obj-$(CONFIG_HAVE_ARM_SCU)	+= smp_scu.o
 obj-$(CONFIG_HAVE_ARM_TWD)	+= smp_twd.o
+obj-$(CONFIG_ARM_ARCH_TIMER)	+= arch_timer.o
 obj-$(CONFIG_DYNAMIC_FTRACE)	+= ftrace.o insn.o
 obj-$(CONFIG_FUNCTION_GRAPH_TRACER)	+= ftrace.o insn.o
 obj-$(CONFIG_JUMP_LABEL)	+= jump_label.o insn.o patch.o

arch/arm/kernel/arch_timer.c

@@ -0,0 +1,288 @@
+/*
+ *  linux/arch/arm/kernel/arch_timer.c
+ *
+ *  Copyright (C) 2011 ARM Ltd.
+ *  All Rights Reserved
+ *
+ * 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.
+ */
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/smp.h>
+#include <linux/cpu.h>
+#include <linux/jiffies.h>
+#include <linux/clockchips.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+
+#include <asm/cputype.h>
+#include <asm/localtimer.h>
+#include <asm/arch_timer.h>
+#include <asm/system_info.h>
+
+static unsigned long arch_timer_rate;
+static int arch_timer_ppi;
+static int arch_timer_ppi2;
+
+static struct clock_event_device __percpu **arch_timer_evt;
+
+/*
+ * Architected system timer support.
+ */
+
+#define ARCH_TIMER_CTRL_ENABLE		(1 << 0)
+#define ARCH_TIMER_CTRL_IT_MASK		(1 << 1)
+#define ARCH_TIMER_CTRL_IT_STAT		(1 << 2)
+
+#define ARCH_TIMER_REG_CTRL		0
+#define ARCH_TIMER_REG_FREQ		1
+#define ARCH_TIMER_REG_TVAL		2
+
+static void arch_timer_reg_write(int reg, u32 val)
+{
+	switch (reg) {
+	case ARCH_TIMER_REG_CTRL:
+		asm volatile("mcr p15, 0, %0, c14, c2, 1" : : "r" (val));
+		break;
+	case ARCH_TIMER_REG_TVAL:
+		asm volatile("mcr p15, 0, %0, c14, c2, 0" : : "r" (val));
+		break;
+	}
+
+	isb();
+}
+
+static u32 arch_timer_reg_read(int reg)
+{
+	u32 val;
+
+	switch (reg) {
+	case ARCH_TIMER_REG_CTRL:
+		asm volatile("mrc p15, 0, %0, c14, c2, 1" : "=r" (val));
+		break;
+	case ARCH_TIMER_REG_FREQ:
+		asm volatile("mrc p15, 0, %0, c14, c0, 0" : "=r" (val));
+		break;
+	case ARCH_TIMER_REG_TVAL:
+		asm volatile("mrc p15, 0, %0, c14, c2, 0" : "=r" (val));
+		break;
+	default:
+		BUG();
+	}
+
+	return val;
+}
+
+static irqreturn_t arch_timer_handler(int irq, void *dev_id)
+{
+	struct clock_event_device *evt = *(struct clock_event_device **)dev_id;
+	unsigned long ctrl;
+
+	ctrl = arch_timer_reg_read(ARCH_TIMER_REG_CTRL);
+	if (ctrl & ARCH_TIMER_CTRL_IT_STAT) {
+		ctrl |= ARCH_TIMER_CTRL_IT_MASK;
+		arch_timer_reg_write(ARCH_TIMER_REG_CTRL, ctrl);
+		evt->event_handler(evt);
+		return IRQ_HANDLED;
+	}
+
+	return IRQ_NONE;
+}
+
+static void arch_timer_disable(void)
+{
+	unsigned long ctrl;
+
+	ctrl = arch_timer_reg_read(ARCH_TIMER_REG_CTRL);
+	ctrl &= ~ARCH_TIMER_CTRL_ENABLE;
+	arch_timer_reg_write(ARCH_TIMER_REG_CTRL, ctrl);
+}
+
+static void arch_timer_set_mode(enum clock_event_mode mode,
+				struct clock_event_device *clk)
+{
+	switch (mode) {
+	case CLOCK_EVT_MODE_UNUSED:
+	case CLOCK_EVT_MODE_SHUTDOWN:
+		arch_timer_disable();
+		break;
+	default:
+		break;
+	}
+}
+
+static int arch_timer_set_next_event(unsigned long evt,
+				     struct clock_event_device *unused)
+{
+	unsigned long ctrl;
+
+	ctrl = arch_timer_reg_read(ARCH_TIMER_REG_CTRL);
+	ctrl |= ARCH_TIMER_CTRL_ENABLE;
+	ctrl &= ~ARCH_TIMER_CTRL_IT_MASK;
+
+	arch_timer_reg_write(ARCH_TIMER_REG_TVAL, evt);
+	arch_timer_reg_write(ARCH_TIMER_REG_CTRL, ctrl);
+
+	return 0;
+}
+
+static int __cpuinit arch_timer_setup(struct clock_event_device *clk)
+{
+	/* Be safe... */
+	arch_timer_disable();
+
+	clk->features = CLOCK_EVT_FEAT_ONESHOT;
+	clk->name = "arch_sys_timer";
+	clk->rating = 450;
+	clk->set_mode = arch_timer_set_mode;
+	clk->set_next_event = arch_timer_set_next_event;
+	clk->irq = arch_timer_ppi;
+
+	clockevents_config_and_register(clk, arch_timer_rate,
+					0xf, 0x7fffffff);
+
+	*__this_cpu_ptr(arch_timer_evt) = clk;
+
+	enable_percpu_irq(clk->irq, 0);
+	if (arch_timer_ppi2)
+		enable_percpu_irq(arch_timer_ppi2, 0);
+
+	return 0;
+}
+
+/* Is the optional system timer available? */
+static int local_timer_is_architected(void)
+{
+	return (cpu_architecture() >= CPU_ARCH_ARMv7) &&
+	       ((read_cpuid_ext(CPUID_EXT_PFR1) >> 16) & 0xf) == 1;
+}
+
+static int arch_timer_available(void)
+{
+	unsigned long freq;
+
+	if (!local_timer_is_architected())
+		return -ENXIO;
+
+	if (arch_timer_rate == 0) {
+		arch_timer_reg_write(ARCH_TIMER_REG_CTRL, 0);
+		freq = arch_timer_reg_read(ARCH_TIMER_REG_FREQ);
+
+		/* Check the timer frequency. */
+		if (freq == 0) {
+			pr_warn("Architected timer frequency not available\n");
+			return -EINVAL;
+		}
+
+		arch_timer_rate = freq;
+	}
+
+	pr_info_once("Architected local timer running at %lu.%02luMHz.\n",
+		     arch_timer_rate / 1000000, (arch_timer_rate / 10000) % 100);
+	return 0;
+}
+
+static inline cycle_t arch_counter_get_cntpct(void)
+{
+	u32 cvall, cvalh;
+
+	asm volatile("mrrc p15, 0, %0, %1, c14" : "=r" (cvall), "=r" (cvalh));
+
+	return ((cycle_t) cvalh << 32) | cvall;
+}
+
+static inline cycle_t arch_counter_get_cntvct(void)
+{
+	u32 cvall, cvalh;
+
+	asm volatile("mrrc p15, 1, %0, %1, c14" : "=r" (cvall), "=r" (cvalh));
+
+	return ((cycle_t) cvalh << 32) | cvall;
+}
+
+static cycle_t arch_counter_read(struct clocksource *cs)
+{
+	return arch_counter_get_cntpct();
+}
+
+static struct clocksource clocksource_counter = {
+	.name	= "arch_sys_counter",
+	.rating	= 400,
+	.read	= arch_counter_read,
+	.mask	= CLOCKSOURCE_MASK(56),
+	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+static void __cpuinit arch_timer_stop(struct clock_event_device *clk)
+{
+	pr_debug("arch_timer_teardown disable IRQ%d cpu #%d\n",
+		 clk->irq, smp_processor_id());
+	disable_percpu_irq(clk->irq);
+	if (arch_timer_ppi2)
+		disable_percpu_irq(arch_timer_ppi2);
+	arch_timer_set_mode(CLOCK_EVT_MODE_UNUSED, clk);
+}
+
+static struct local_timer_ops arch_timer_ops __cpuinitdata = {
+	.setup	= arch_timer_setup,
+	.stop	= arch_timer_stop,
+};
+
+int __init arch_timer_register(struct arch_timer *at)
+{
+	int err;
+
+	if (at->res[0].start <= 0 || !(at->res[0].flags & IORESOURCE_IRQ))
+		return -EINVAL;
+
+	err = arch_timer_available();
+	if (err)
+		return err;
+
+	arch_timer_evt = alloc_percpu(struct clock_event_device *);
+	if (!arch_timer_evt)
+		return -ENOMEM;
+
+	clocksource_register_hz(&clocksource_counter, arch_timer_rate);
+
+	arch_timer_ppi = at->res[0].start;
+	err = request_percpu_irq(arch_timer_ppi, arch_timer_handler,
+				 "arch_timer", arch_timer_evt);
+	if (err) {
+		pr_err("arch_timer: can't register interrupt %d (%d)\n",
+		       arch_timer_ppi, err);
+		goto out_free;
+	}
+
+	if (at->res[1].start > 0 || (at->res[1].flags & IORESOURCE_IRQ)) {
+		arch_timer_ppi2 = at->res[1].start;
+		err = request_percpu_irq(arch_timer_ppi2, arch_timer_handler,
+					 "arch_timer", arch_timer_evt);
+		if (err) {
+			pr_err("arch_timer: can't register interrupt %d (%d)\n",
+			       arch_timer_ppi2, err);
+			arch_timer_ppi2 = 0;
+			goto out_free_irq;
+		}
+	}
+
+	err = local_timer_register(&arch_timer_ops);
+	if (err)
+		goto out_free_irq;
+
+	return 0;
+
+out_free_irq:
+	free_percpu_irq(arch_timer_ppi, arch_timer_evt);
+	if (arch_timer_ppi2)
+		free_percpu_irq(arch_timer_ppi2, arch_timer_evt);
+
+out_free:
+	free_percpu(arch_timer_evt);
+
+	return err;
+}