[ARM SMP] Add local timer support for Realview MPcore

Add platform specific parts for local timer support for the
Realview board.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

4 files changed, 137 insertions, 1 deletions

diff --git a/arch/arm/mach-realview/Makefile b/arch/arm/mach-realview/Makefile
index 011a85c..a6a40da 100644
--- a/arch/arm/mach-realview/Makefile
+++ b/arch/arm/mach-realview/Makefile
@@ -5,3 +5,4 @@
 obj-y					:= core.o clock.o
 obj-$(CONFIG_MACH_REALVIEW_EB)		+= realview_eb.o
 obj-$(CONFIG_SMP)			+= platsmp.o headsmp.o
+obj-$(CONFIG_LOCAL_TIMERS)		+= localtimer.o
diff --git a/arch/arm/mach-realview/core.c b/arch/arm/mach-realview/core.c
index 4ea60d8..e2c6fa2 100644
--- a/arch/arm/mach-realview/core.c
+++ b/arch/arm/mach-realview/core.c
@@ -550,7 +550,7 @@ static irqreturn_t realview_timer_interrupt(int irq, void *dev_id, struct pt_reg
 
 	timer_tick(regs);
 
-#ifdef CONFIG_SMP
+#if defined(CONFIG_SMP) && !defined(CONFIG_LOCAL_TIMERS)
 	smp_send_timer();
 	update_process_times(user_mode(regs));
 #endif
diff --git a/arch/arm/mach-realview/localtimer.c b/arch/arm/mach-realview/localtimer.c
new file mode 100644
index 0000000..5e917e3
--- /dev/null
+++ b/arch/arm/mach-realview/localtimer.c
@@ -0,0 +1,130 @@
+/*
+ *  linux/arch/arm/mach-realview/localtimer.c
+ *
+ *  Copyright (C) 2002 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 <asm/mach/time.h>
+#include <asm/hardware/arm_twd.h>
+#include <asm/hardware/gic.h>
+#include <asm/hardware.h>
+#include <asm/io.h>
+#include <asm/irq.h>
+
+#include "core.h"
+
+#define TWD_BASE(cpu)	(__io_address(REALVIEW_TWD_BASE) + \
+			 ((cpu) * REALVIEW_TWD_SIZE))
+
+static unsigned long mpcore_timer_rate;
+
+/*
+ * local_timer_ack: checks for a local timer interrupt.
+ *
+ * If a local timer interrupt has occured, acknowledge and return 1.
+ * Otherwise, return 0.
+ */
+int local_timer_ack(void)
+{
+	void __iomem *base = TWD_BASE(smp_processor_id());
+
+	if (__raw_readl(base + TWD_TIMER_INTSTAT)) {
+		__raw_writel(1, base + TWD_TIMER_INTSTAT);
+		return 1;
+	}
+
+	return 0;
+}
+
+void __cpuinit local_timer_setup(unsigned int cpu)
+{
+	void __iomem *base = TWD_BASE(cpu);
+	unsigned int load, offset;
+	u64 waitjiffies;
+	unsigned int count;
+
+	/*
+	 * If this is the first time round, we need to work out how fast
+	 * the timer ticks
+	 */
+	if (mpcore_timer_rate == 0) {
+		printk("Calibrating local timer... ");
+
+		/* Wait for a tick to start */
+		waitjiffies = get_jiffies_64() + 1;
+
+		while (get_jiffies_64() < waitjiffies)
+			udelay(10);
+
+		/* OK, now the tick has started, let's get the timer going */
+		waitjiffies += 5;
+
+				 /* enable, no interrupt or reload */
+		__raw_writel(0x1, base + TWD_TIMER_CONTROL);
+
+				 /* maximum value */
+		__raw_writel(0xFFFFFFFFU, base + TWD_TIMER_COUNTER);
+
+		while (get_jiffies_64() < waitjiffies)
+			udelay(10);
+
+		count = __raw_readl(base + TWD_TIMER_COUNTER);
+
+		mpcore_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
+
+		printk("%lu.%02luMHz.\n", mpcore_timer_rate / 1000000,
+			(mpcore_timer_rate / 100000) % 100);
+	}
+
+	load = mpcore_timer_rate / HZ;
+
+	__raw_writel(load, base + TWD_TIMER_LOAD);
+	__raw_writel(0x7,  base + TWD_TIMER_CONTROL);
+
+	/*
+	 * Now maneuver our local tick into the right part of the jiffy.
+	 * Start by working out where within the tick our local timer
+	 * interrupt should go.
+	 */
+	offset = ((mpcore_timer_rate / HZ) / (NR_CPUS + 1)) * (cpu + 1);
+
+	/*
+	 * gettimeoffset() will return a number of us since the last tick.
+	 * Convert this number of us to a local timer tick count.
+	 * Be careful of integer overflow whilst keeping maximum precision.
+	 *
+	 * with HZ=100 and 1MHz (fpga) ~ 1GHz processor:
+	 * load = 1 ~ 10,000
+	 * mpcore_timer_rate/10000 = 100 ~ 100,000
+	 *
+	 * so the multiply value will be less than 10^9 always.
+	 */
+	load = (system_timer->offset() * (mpcore_timer_rate / 10000)) / 100;
+
+	/* Add on our offset to get the load value */
+	load = (load + offset) % (mpcore_timer_rate / HZ);
+
+	__raw_writel(load, base + TWD_TIMER_COUNTER);
+
+	/* Make sure our local interrupt controller has this enabled */
+	__raw_writel(1 << IRQ_LOCALTIMER,
+		     __io_address(REALVIEW_GIC_DIST_BASE) + GIC_DIST_ENABLE_SET);
+}
+
+/*
+ * take a local timer down
+ */
+void __cpuexit local_timer_stop(unsigned int cpu)
+{
+	__raw_writel(0, TWD_BASE(cpu) + TWD_TIMER_CONTROL);
+}
diff --git a/arch/arm/mach-realview/platsmp.c b/arch/arm/mach-realview/platsmp.c
index 09b35f6..0c7d4ac 100644
--- a/arch/arm/mach-realview/platsmp.c
+++ b/arch/arm/mach-realview/platsmp.c
@@ -175,6 +175,11 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
 		max_cpus = ncores;
 
 	/*
+	 * Enable the local timer for primary CPU
+	 */
+	local_timer_setup(cpu);
+
+	/*
 	 * Initialise the possible/present maps.
 	 * cpu_possible_map describes the set of CPUs which may be present
 	 * cpu_present_map describes the set of CPUs populated