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+/*
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+ * linux/arch/arm/mach-realview/localtimer.c
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+ *
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+ * Copyright (C) 2002 ARM Ltd.
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+ * All Rights Reserved
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+ *
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+ * This program is free software; you can redistribute it and/or modify
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+ * it under the terms of the GNU General Public License version 2 as
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+ * published by the Free Software Foundation.
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+ */
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+#include <linux/init.h>
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+#include <linux/kernel.h>
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+#include <linux/delay.h>
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+#include <linux/device.h>
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+#include <linux/smp.h>
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+
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+#include <asm/mach/time.h>
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+#include <asm/hardware/arm_twd.h>
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+#include <asm/hardware/gic.h>
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+#include <asm/hardware.h>
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+#include <asm/io.h>
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+#include <asm/irq.h>
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+
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+#include "core.h"
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+
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+#define TWD_BASE(cpu) (__io_address(REALVIEW_TWD_BASE) + \
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+ ((cpu) * REALVIEW_TWD_SIZE))
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+
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+static unsigned long mpcore_timer_rate;
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+
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+/*
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+ * local_timer_ack: checks for a local timer interrupt.
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+ *
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+ * If a local timer interrupt has occured, acknowledge and return 1.
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+ * Otherwise, return 0.
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+ */
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+int local_timer_ack(void)
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+{
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+ void __iomem *base = TWD_BASE(smp_processor_id());
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+
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+ if (__raw_readl(base + TWD_TIMER_INTSTAT)) {
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+ __raw_writel(1, base + TWD_TIMER_INTSTAT);
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+ return 1;
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+ }
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+
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+ return 0;
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+}
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+
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+void __cpuinit local_timer_setup(unsigned int cpu)
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+{
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+ void __iomem *base = TWD_BASE(cpu);
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+ unsigned int load, offset;
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+ u64 waitjiffies;
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+ unsigned int count;
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+
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+ /*
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+ * If this is the first time round, we need to work out how fast
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+ * the timer ticks
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+ */
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+ if (mpcore_timer_rate == 0) {
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+ printk("Calibrating local timer... ");
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+
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+ /* Wait for a tick to start */
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+ waitjiffies = get_jiffies_64() + 1;
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+
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+ while (get_jiffies_64() < waitjiffies)
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+ udelay(10);
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+
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+ /* OK, now the tick has started, let's get the timer going */
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+ waitjiffies += 5;
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+
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+ /* enable, no interrupt or reload */
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+ __raw_writel(0x1, base + TWD_TIMER_CONTROL);
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+
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+ /* maximum value */
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+ __raw_writel(0xFFFFFFFFU, base + TWD_TIMER_COUNTER);
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+
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+ while (get_jiffies_64() < waitjiffies)
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+ udelay(10);
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+
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+ count = __raw_readl(base + TWD_TIMER_COUNTER);
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+
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+ mpcore_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
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+
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+ printk("%lu.%02luMHz.\n", mpcore_timer_rate / 1000000,
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+ (mpcore_timer_rate / 100000) % 100);
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+ }
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+
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+ load = mpcore_timer_rate / HZ;
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+
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+ __raw_writel(load, base + TWD_TIMER_LOAD);
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+ __raw_writel(0x7, base + TWD_TIMER_CONTROL);
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+
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+ /*
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+ * Now maneuver our local tick into the right part of the jiffy.
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+ * Start by working out where within the tick our local timer
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+ * interrupt should go.
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+ */
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+ offset = ((mpcore_timer_rate / HZ) / (NR_CPUS + 1)) * (cpu + 1);
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+
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+ /*
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+ * gettimeoffset() will return a number of us since the last tick.
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+ * Convert this number of us to a local timer tick count.
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+ * Be careful of integer overflow whilst keeping maximum precision.
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+ *
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+ * with HZ=100 and 1MHz (fpga) ~ 1GHz processor:
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+ * load = 1 ~ 10,000
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+ * mpcore_timer_rate/10000 = 100 ~ 100,000
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+ *
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+ * so the multiply value will be less than 10^9 always.
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+ */
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+ load = (system_timer->offset() * (mpcore_timer_rate / 10000)) / 100;
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+
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+ /* Add on our offset to get the load value */
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+ load = (load + offset) % (mpcore_timer_rate / HZ);
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+
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+ __raw_writel(load, base + TWD_TIMER_COUNTER);
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+
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+ /* Make sure our local interrupt controller has this enabled */
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+ __raw_writel(1 << IRQ_LOCALTIMER,
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+ __io_address(REALVIEW_GIC_DIST_BASE) + GIC_DIST_ENABLE_SET);
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+}
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+
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+/*
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+ * take a local timer down
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+ */
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+void __cpuexit local_timer_stop(unsigned int cpu)
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+{
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+ __raw_writel(0, TWD_BASE(cpu) + TWD_TIMER_CONTROL);
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+}
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Russell King