Date:	Wed, 5 Dec 2012 16:08:40 +0000
From:	James Hogan <james.hogan@...tec.com>
To:	<linux-arch@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:	Arnd Bergmann <arnd@...db.de>, James Hogan <james.hogan@...tec.com>
Subject: [PATCH v2 22/44] 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@...tec.com>
---
 arch/metag/include/asm/clock.h     |   51 +++++++++++
 arch/metag/include/asm/delay.h     |   29 +++++++
 arch/metag/include/asm/mach/arch.h |    4 +
 arch/metag/kernel/clock.c          |   53 ++++++++++++
 arch/metag/kernel/time.c           |  163 ++++++++++++++++++++++++++++++++++++
 5 files changed, 300 insertions(+), 0 deletions(-)
 create mode 100644 arch/metag/include/asm/clock.h
 create mode 100644 arch/metag/include/asm/delay.h
 create mode 100644 arch/metag/kernel/clock.c
 create mode 100644 arch/metag/kernel/time.c

diff --git a/arch/metag/include/asm/clock.h b/arch/metag/include/asm/clock.h
new file mode 100644
index 0000000..3e2915a
--- /dev/null
+++ b/arch/metag/include/asm/clock.h
@@ -0,0 +1,51 @@
+/*
+ * arch/metag/include/asm/clock.h
+ *
+ * Copyright (C) 2012 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.
+ */
+
+#ifndef _METAG_CLOCK_H_
+#define _METAG_CLOCK_H_
+
+#include <asm/mach/arch.h>
+
+/**
+ * struct meta_clock_desc - Meta Core clock callbacks.
+ * @get_core_freq:	Get the frequency of the Meta core. If this is NULL, the
+ *			core frequency will be determined like this:
+ *			Meta 1: based on loops_per_jiffy.
+ *			Meta 2: (EXPAND_TIMER_DIV + 1) MHz.
+ */
+struct meta_clock_desc {
+	unsigned long		(*get_core_freq)(void);
+};
+
+extern struct meta_clock_desc _meta_clock;
+
+/*
+ * Set up the default clock, ensuring all callbacks are valid - only accessible
+ * during boot.
+ */
+void setup_meta_clocks(struct meta_clock_desc *desc);
+
+/**
+ * get_coreclock() - Get the frequency of the Meta core clock.
+ *
+ * Returns:	The Meta core clock frequency in Hz.
+ */
+static inline unsigned long get_coreclock(void)
+{
+	/*
+	 * Use the current clock callback. If set correctly this will provide
+	 * the most accurate frequency as it can be calculated directly from the
+	 * PLL configuration. otherwise a default callback will have been set
+	 * instead.
+	 */
+	return _meta_clock.get_core_freq();
+}
+
+#endif /* _METAG_CLOCK_H_ */
diff --git a/arch/metag/include/asm/delay.h b/arch/metag/include/asm/delay.h
new file mode 100644
index 0000000..9c92f99
--- /dev/null
+++ b/arch/metag/include/asm/delay.h
@@ -0,0 +1,29 @@
+#ifndef _METAG_DELAY_H
+#define _METAG_DELAY_H
+
+/*
+ * Copyright (C) 1993 Linus Torvalds
+ *
+ * Delay routines calling functions in arch/metag/lib/delay.c
+ */
+
+/* Undefined functions to get compile-time errors */
+extern void __bad_udelay(void);
+extern void __bad_ndelay(void);
+
+extern void __udelay(unsigned long usecs);
+extern void __ndelay(unsigned long nsecs);
+extern void __const_udelay(unsigned long xloops);
+extern void __delay(unsigned long loops);
+
+/* 0x10c7 is 2**32 / 1000000 (rounded up) */
+#define udelay(n) (__builtin_constant_p(n) ? \
+	((n) > 20000 ? __bad_udelay() : __const_udelay((n) * 0x10c7ul)) : \
+	__udelay(n))
+
+/* 0x5 is 2**32 / 1000000000 (rounded up) */
+#define ndelay(n) (__builtin_constant_p(n) ? \
+	((n) > 20000 ? __bad_ndelay() : __const_udelay((n) * 5ul)) : \
+	__ndelay(n))
+
+#endif /* _METAG_DELAY_H */
diff --git a/arch/metag/include/asm/mach/arch.h b/arch/metag/include/asm/mach/arch.h
index 8429c76..230d896 100644
--- a/arch/metag/include/asm/mach/arch.h
+++ b/arch/metag/include/asm/mach/arch.h
@@ -16,10 +16,13 @@
 
 #include <linux/stddef.h>
 
+#include <asm/clock.h>
+
 /**
  * struct machine_desc - Describes a board controlled by a Meta.
  * @name:		Board/SoC name.
  * @dt_compat:		Array of device tree 'compatible' strings.
+ * @clocks:		Clock callbacks.
  *
  * @init_early:		Early init callback.
  * @init_irq:		IRQ init callback for setting up IRQ controllers.
@@ -34,6 +37,7 @@
 struct machine_desc {
 	const char		*name;
 	const char		**dt_compat;
+	struct meta_clock_desc	*clocks;
 
 	void			(*init_early)(void);
 	void			(*init_irq)(void);
diff --git a/arch/metag/kernel/clock.c b/arch/metag/kernel/clock.c
new file mode 100644
index 0000000..defc840
--- /dev/null
+++ b/arch/metag/kernel/clock.c
@@ -0,0 +1,53 @@
+/*
+ * arch/metag/kernel/clock.c
+ *
+ * Copyright (C) 2012 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.
+ */
+
+#include <linux/delay.h>
+#include <linux/io.h>
+
+#include <asm/param.h>
+#include <asm/clock.h>
+
+struct meta_clock_desc _meta_clock;
+
+/* Default machine get_core_freq callback. */
+static unsigned long get_core_freq_default(void)
+{
+#ifdef CONFIG_METAG_META21
+	/*
+	 * Meta 2 cores divide down the core clock for the Meta timers, so we
+	 * can estimate the core clock from the divider.
+	 */
+	return (metag_in32(EXPAND_TIMER_DIV) + 1) * 1000000;
+#else
+	/*
+	 * On Meta 1 we don't know the core clock, but assuming the Meta timer
+	 * is correct it can be estimated based on loops_per_jiffy.
+	 */
+	return (loops_per_jiffy * HZ * 5) >> 1;
+#endif
+}
+
+/**
+ * setup_meta_clocks() - Set up the Meta clock.
+ * @desc:	Clock descriptor usually provided by machine description
+ *
+ * Ensures all callbacks are valid.
+ */
+void __init setup_meta_clocks(struct meta_clock_desc *desc)
+{
+	/* copy callbacks */
+	if (desc)
+		_meta_clock = *desc;
+
+	/* set fallback functions */
+	if (!_meta_clock.get_core_freq)
+		_meta_clock.get_core_freq = get_core_freq_default;
+}
+
diff --git a/arch/metag/kernel/time.c b/arch/metag/kernel/time.c
new file mode 100644
index 0000000..6df41b8
--- /dev/null
+++ b/arch/metag/kernel/time.c
@@ -0,0 +1,163 @@
+/*
+ * Copyright (C) 2005,2006,2007,2008 Imagination Technologies Ltd.
+ *
+ * This file contains the Meta-specific time handling details.
+ *
+ */
+
+#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)
+{
+	TBI_SETREG(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 inline cycle_t txtimer_read(void)
+{
+	unsigned int ret;
+
+	__asm__ volatile ("MOV	%0, TXTIMER\n" : "=r" (ret));
+	return ret;
+}
+
+static cycle_t metag_clocksource_read(struct clocksource *cs)
+{
+	return txtimer_read();
+}
+
+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 = txtimer_read();
+	return ticks << HARDWARE_TO_NS_SHIFT;
+}
+
+void __cpuinit local_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 = TBI_GETREG(TXDIVTIME);
+
+	txdivtime &= ~TXDIVTIME_DIV_BITS;
+	txdivtime |= (HARDWARE_DIV & TXDIVTIME_DIV_BITS);
+
+	TBI_SETREG(TXDIVTIME, txdivtime);
+
+	sprintf(name, "META %d", cpu);
+	clk->name = name;
+	clk->features = CLOCK_EVT_FEAT_ONESHOT,
+
+	clk->rating = 200,
+	clk->shift = 12,
+	clk->irq = 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);
+
+		asm volatile("MOV TXTIMER, %0\n" : : "r" (val));
+	}
+}
+
+void __init time_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(TBID_SIGNUM_TRT, &metag_timer_irq);
+
+	local_timer_setup(smp_processor_id());
+}
-- 
1.7.7.6


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