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- /*
- * 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 <linux/jiffies.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>
- #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);
- }
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