metag: Time keeping

Add time keeping code for metag. Meta hardware threads have 2 timers.
The background timer (TXTIMER) is used as a free-running time base, and
the interrupt timer (TXTIMERI) is used for the timer interrupt. Both
counters traditionally count at approximately 1MHz.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: John Stultz <johnstul@us.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>

3 files changed, 204 insertions, 0 deletions

diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 7fdcbd3f4da..75bc7520ace 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -58,3 +58,8 @@ config CLKSRC_ARM_GENERIC
 	def_bool y if ARM64
 	help
 	  This option enables support for the ARM generic timer.
+
+config CLKSRC_METAG_GENERIC
+	def_bool y if METAG
+	help
+	  This option enables support for the Meta per-thread timers.
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index f93453d0167..09dcd49b7e3 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -18,3 +18,4 @@ obj-$(CONFIG_ARCH_BCM2835)	+= bcm2835_timer.o
 obj-$(CONFIG_SUNXI_TIMER)	+= sunxi_timer.o
 
 obj-$(CONFIG_CLKSRC_ARM_GENERIC)	+= arm_generic.o
+obj-$(CONFIG_CLKSRC_METAG_GENERIC)	+= metag_generic.o
diff --git a/drivers/clocksource/metag_generic.c b/drivers/clocksource/metag_generic.c
new file mode 100644
index 00000000000..ade7513a11d
--- /dev/null
+++ b/drivers/clocksource/metag_generic.c
@@ -0,0 +1,198 @@
+/*
+ * Copyright (C) 2005-2013 Imagination Technologies Ltd.
+ *
+ * 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.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *
+ * Support for Meta per-thread timers.
+ *
+ * Meta hardware threads have 2 timers. The background timer (TXTIMER) is used
+ * as a free-running time base (hz clocksource), and the interrupt timer
+ * (TXTIMERI) is used for the timer interrupt (clock event). Both counters
+ * traditionally count at approximately 1MHz.
+ */
+
+#include <clocksource/metag_generic.h>
+#include <linux/cpu.h>
+#include <linux/errno.h>
+#include <linux/sched.h>
+#include <linux/kernel.h>
+#include <linux/param.h>
+#include <linux/time.h>
+#include <linux/init.h>
+#include <linux/proc_fs.h>
+#include <linux/clocksource.h>
+#include <linux/clockchips.h>
+#include <linux/interrupt.h>
+
+#include <asm/clock.h>
+#include <asm/hwthread.h>
+#include <asm/core_reg.h>
+#include <asm/metag_mem.h>
+#include <asm/tbx.h>
+
+#define HARDWARE_FREQ		1000000	/* 1MHz */
+#define HARDWARE_DIV		1	/* divide by 1 = 1MHz clock */
+#define HARDWARE_TO_NS_SHIFT	10	/* convert ticks to ns */
+
+static unsigned int hwtimer_freq = HARDWARE_FREQ;
+static DEFINE_PER_CPU(struct clock_event_device, local_clockevent);
+static DEFINE_PER_CPU(char [11], local_clockevent_name);
+
+static int metag_timer_set_next_event(unsigned long delta,
+				      struct clock_event_device *dev)
+{
+	__core_reg_set(TXTIMERI, -delta);
+	return 0;
+}
+
+static void metag_timer_set_mode(enum clock_event_mode mode,
+				 struct clock_event_device *evt)
+{
+	switch (mode) {
+	case CLOCK_EVT_MODE_ONESHOT:
+	case CLOCK_EVT_MODE_RESUME:
+		break;
+
+	case CLOCK_EVT_MODE_SHUTDOWN:
+		/* We should disable the IRQ here */
+		break;
+
+	case CLOCK_EVT_MODE_PERIODIC:
+	case CLOCK_EVT_MODE_UNUSED:
+		WARN_ON(1);
+		break;
+	};
+}
+
+static cycle_t metag_clocksource_read(struct clocksource *cs)
+{
+	return __core_reg_get(TXTIMER);
+}
+
+static struct clocksource clocksource_metag = {
+	.name = "META",
+	.rating = 200,
+	.mask = CLOCKSOURCE_MASK(32),
+	.read = metag_clocksource_read,
+	.flags = CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+static irqreturn_t metag_timer_interrupt(int irq, void *dummy)
+{
+	struct clock_event_device *evt = &__get_cpu_var(local_clockevent);
+
+	evt->event_handler(evt);
+
+	return IRQ_HANDLED;
+}
+
+static struct irqaction metag_timer_irq = {
+	.name = "META core timer",
+	.handler = metag_timer_interrupt,
+	.flags = IRQF_TIMER | IRQF_IRQPOLL | IRQF_PERCPU,
+};
+
+unsigned long long sched_clock(void)
+{
+	unsigned long long ticks = __core_reg_get(TXTIMER);
+	return ticks << HARDWARE_TO_NS_SHIFT;
+}
+
+static void __cpuinit arch_timer_setup(unsigned int cpu)
+{
+	unsigned int txdivtime;
+	struct clock_event_device *clk = &per_cpu(local_clockevent, cpu);
+	char *name = per_cpu(local_clockevent_name, cpu);
+
+	txdivtime = __core_reg_get(TXDIVTIME);
+
+	txdivtime &= ~TXDIVTIME_DIV_BITS;
+	txdivtime |= (HARDWARE_DIV & TXDIVTIME_DIV_BITS);
+
+	__core_reg_set(TXDIVTIME, txdivtime);
+
+	sprintf(name, "META %d", cpu);
+	clk->name = name;
+	clk->features = CLOCK_EVT_FEAT_ONESHOT,
+
+	clk->rating = 200,
+	clk->shift = 12,
+	clk->irq = tbisig_map(TBID_SIGNUM_TRT),
+	clk->set_mode = metag_timer_set_mode,
+	clk->set_next_event = metag_timer_set_next_event,
+
+	clk->mult = div_sc(hwtimer_freq, NSEC_PER_SEC, clk->shift);
+	clk->max_delta_ns = clockevent_delta2ns(0x7fffffff, clk);
+	clk->min_delta_ns = clockevent_delta2ns(0xf, clk);
+	clk->cpumask = cpumask_of(cpu);
+
+	clockevents_register_device(clk);
+
+	/*
+	 * For all non-boot CPUs we need to synchronize our free
+	 * running clock (TXTIMER) with the boot CPU's clock.
+	 *
+	 * While this won't be accurate, it should be close enough.
+	 */
+	if (cpu) {
+		unsigned int thread0 = cpu_2_hwthread_id[0];
+		unsigned long val;
+
+		val = core_reg_read(TXUCT_ID, TXTIMER_REGNUM, thread0);
+		__core_reg_set(TXTIMER, val);
+	}
+}
+
+static int __cpuinit arch_timer_cpu_notify(struct notifier_block *self,
+					   unsigned long action, void *hcpu)
+{
+	int cpu = (long)hcpu;
+
+	switch (action) {
+	case CPU_STARTING:
+	case CPU_STARTING_FROZEN:
+		arch_timer_setup(cpu);
+		break;
+	}
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block __cpuinitdata arch_timer_cpu_nb = {
+	.notifier_call = arch_timer_cpu_notify,
+};
+
+int __init metag_generic_timer_init(void)
+{
+	/*
+	 * On Meta 2 SoCs, the actual frequency of the timer is based on the
+	 * Meta core clock speed divided by an integer, so it is only
+	 * approximately 1MHz. Calculating the real frequency here drastically
+	 * reduces clock skew on these SoCs.
+	 */
+#ifdef CONFIG_METAG_META21
+	hwtimer_freq = get_coreclock() / (metag_in32(EXPAND_TIMER_DIV) + 1);
+#endif
+	clocksource_register_hz(&clocksource_metag, hwtimer_freq);
+
+	setup_irq(tbisig_map(TBID_SIGNUM_TRT), &metag_timer_irq);
+
+	/* Configure timer on boot CPU */
+	arch_timer_setup(smp_processor_id());
+
+	/* Hook cpu boot to configure other CPU's timers */
+	register_cpu_notifier(&arch_timer_cpu_nb);
+
+	return 0;
+}