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/*
* arch/arm/mach-tegra/localtimer.c
*
* CPU local timer support for SMP Tegra SoCs
*
* Copyright (c) 2008-2009, NVIDIA Corporation.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* 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, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
/*
* For SMP, linux needs one local timer per CPU. This is in addition to the
* global timner that the linux requires. These local timers can be either a
* seperate timer hardware one per CPU or can be key'ed off the global timer
* using the IPI timer broadcast mechanism.
*
*/
#include <linux/time.h>
#include <linux/smp.h>
#include <linux/percpu.h>
#include <linux/clockchips.h>
#include <asm/smp_twd.h>
#include "mach/timex.h"
#if defined(CONFIG_ARCH_TEGRA_2x_SOC)
#define LOCAL_TIMER_ADDR 0x50040600UL
#define LOCAL_TIMER_IRQ 29
#define CPU_FREQ_SCALE_SHIFT 24
#define CPU_FREQ_SCALE_DIVIDER (0x1 << CPU_FREQ_SCALE_SHIFT)
#define CPU_FREQ_SCALE_INIT 125
#else
#error "Unsupported Tegra SoC family"
#endif
#if defined(CONFIG_LOCAL_TIMERS) && defined(CONFIG_HAVE_ARM_TWD)
#if defined(CONFIG_USE_ARM_TWD_PRESCALER)
/*
* Find new prescaler value for cpu frequency changes, so that local timer
* input frequency is kept at calibration level. Save new value in shadow
* variable - do not update h/w.
*/
void local_timer_rescale(unsigned long cpu_freq_khz)
{
static unsigned long cpu_freq_scale_mult = 0;
unsigned long scale;
/* 1st call at boot/calibration frequency */
if (cpu_freq_scale_mult == 0) {
cpu_freq_scale_mult = ((timer_prescaler + 1) <<
CPU_FREQ_SCALE_SHIFT) / cpu_freq_khz;
printk("Local timer scaling factor %lu, shift %d\n",
cpu_freq_scale_mult, CPU_FREQ_SCALE_SHIFT);
return;
}
scale = (unsigned long)((((uint64_t)cpu_freq_khz * cpu_freq_scale_mult)
+ CPU_FREQ_SCALE_DIVIDER -1) >> CPU_FREQ_SCALE_SHIFT);
timer_prescaler = scale - 1;
}
#endif
void __cpuinit local_timer_setup(struct clock_event_device *clk)
{
#if defined(CONFIG_USE_ARM_TWD_PRESCALER)
if (timer_prescaler == 0)
timer_prescaler = CPU_FREQ_SCALE_INIT - 1;
#endif
twd_base = IO_ADDRESS(LOCAL_TIMER_ADDR);
clk->irq = LOCAL_TIMER_IRQ;
twd_timer_setup(clk);
}
#endif
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