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* arch/arm/plat-spear/time.c
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* Copyright (C) 2009 ST Microelectronics
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* Shiraz Hashim<shiraz.hashim@st.com>
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* This file is licensed under the terms of the GNU General Public
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* License version 2. This program is licensed "as is" without any
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* warranty of any kind, whether express or implied.
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#include <linux/clk.h>
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#include <linux/clockchips.h>
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#include <linux/clocksource.h>
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#include <linux/err.h>
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#include <linux/init.h>
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#include <linux/interrupt.h>
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#include <linux/kernel.h>
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#include <linux/time.h>
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#include <linux/irq.h>
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#include <asm/mach/time.h>
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#include <mach/irqs.h>
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#include <mach/hardware.h>
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#include <mach/spear.h>
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#include <mach/generic.h>
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* We would use TIMER0 and TIMER1 as clockevent and clocksource.
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* Timer0 and Timer1 both belong to same gpt block in cpu subbsystem. Further
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* they share same functional clock. Any change in one's functional clock will
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* also affect other timer.
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#define CLKEVT 0 /* gpt0, channel0 as clockevent */
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#define CLKSRC 1 /* gpt0, channel1 as clocksource */
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/* Register offsets, x is channel number */
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#define CR(x) ((x) * 0x80 + 0x80)
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#define IR(x) ((x) * 0x80 + 0x84)
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#define LOAD(x) ((x) * 0x80 + 0x88)
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#define COUNT(x) ((x) * 0x80 + 0x8C)
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/* Reg bit definitions */
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#define CTRL_INT_ENABLE 0x0100
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#define CTRL_ENABLE 0x0020
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#define CTRL_ONE_SHOT 0x0010
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#define CTRL_PRESCALER1 0x0
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#define CTRL_PRESCALER2 0x1
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#define CTRL_PRESCALER4 0x2
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#define CTRL_PRESCALER8 0x3
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#define CTRL_PRESCALER16 0x4
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#define CTRL_PRESCALER32 0x5
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#define CTRL_PRESCALER64 0x6
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#define CTRL_PRESCALER128 0x7
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#define CTRL_PRESCALER256 0x8
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#define INT_STATUS 0x1
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* Minimum clocksource/clockevent timer range in seconds
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#define SPEAR_MIN_RANGE 4
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static __iomem void *gpt_base;
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static struct clk *gpt_clk;
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static void clockevent_set_mode(enum clock_event_mode mode,
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struct clock_event_device *clk_event_dev);
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static int clockevent_next_event(unsigned long evt,
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struct clock_event_device *clk_event_dev);
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static cycle_t clocksource_read_cycles(struct clocksource *cs)
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return (cycle_t) readw(gpt_base + COUNT(CLKSRC));
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static struct clocksource clksrc = {
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.rating = 200, /* its a pretty decent clock */
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.read = clocksource_read_cycles,
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.mask = 0xFFFF, /* 16 bits */
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.flags = CLOCK_SOURCE_IS_CONTINUOUS,
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static void spear_clocksource_init(void)
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/* program the prescaler (/256)*/
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writew(CTRL_PRESCALER256, gpt_base + CR(CLKSRC));
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/* find out actual clock driving Timer */
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tick_rate = clk_get_rate(gpt_clk);
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tick_rate >>= CTRL_PRESCALER256;
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writew(0xFFFF, gpt_base + LOAD(CLKSRC));
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val = readw(gpt_base + CR(CLKSRC));
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val &= ~CTRL_ONE_SHOT; /* autoreload mode */
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writew(val, gpt_base + CR(CLKSRC));
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/* register the clocksource */
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clocksource_register_hz(&clksrc, tick_rate);
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static struct clock_event_device clkevt = {
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.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
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.set_mode = clockevent_set_mode,
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.set_next_event = clockevent_next_event,
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.shift = 0, /* to be computed */
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static void clockevent_set_mode(enum clock_event_mode mode,
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struct clock_event_device *clk_event_dev)
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val = readw(gpt_base + CR(CLKEVT));
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writew(val, gpt_base + CR(CLKEVT));
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case CLOCK_EVT_MODE_PERIODIC:
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period = clk_get_rate(gpt_clk) / HZ;
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period >>= CTRL_PRESCALER16;
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writew(period, gpt_base + LOAD(CLKEVT));
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val = readw(gpt_base + CR(CLKEVT));
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val &= ~CTRL_ONE_SHOT;
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val |= CTRL_ENABLE | CTRL_INT_ENABLE;
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writew(val, gpt_base + CR(CLKEVT));
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case CLOCK_EVT_MODE_ONESHOT:
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val = readw(gpt_base + CR(CLKEVT));
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val |= CTRL_ONE_SHOT;
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writew(val, gpt_base + CR(CLKEVT));
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case CLOCK_EVT_MODE_UNUSED:
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case CLOCK_EVT_MODE_SHUTDOWN:
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case CLOCK_EVT_MODE_RESUME:
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pr_err("Invalid mode requested\n");
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static int clockevent_next_event(unsigned long cycles,
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struct clock_event_device *clk_event_dev)
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writew(cycles, gpt_base + LOAD(CLKEVT));
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val = readw(gpt_base + CR(CLKEVT));
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val |= CTRL_ENABLE | CTRL_INT_ENABLE;
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writew(val, gpt_base + CR(CLKEVT));
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static irqreturn_t spear_timer_interrupt(int irq, void *dev_id)
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struct clock_event_device *evt = &clkevt;
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writew(INT_STATUS, gpt_base + IR(CLKEVT));
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evt->event_handler(evt);
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static struct irqaction spear_timer_irq = {
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.flags = IRQF_DISABLED | IRQF_TIMER,
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.handler = spear_timer_interrupt
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static void __init spear_clockevent_init(void)
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/* program the prescaler */
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writew(CTRL_PRESCALER16, gpt_base + CR(CLKEVT));
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tick_rate = clk_get_rate(gpt_clk);
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tick_rate >>= CTRL_PRESCALER16;
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clockevents_calc_mult_shift(&clkevt, tick_rate, SPEAR_MIN_RANGE);
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clkevt.max_delta_ns = clockevent_delta2ns(0xfff0,
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clkevt.min_delta_ns = clockevent_delta2ns(3, &clkevt);
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clkevt.cpumask = cpumask_of(0);
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clockevents_register_device(&clkevt);
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setup_irq(SPEAR_GPT0_CHAN0_IRQ, &spear_timer_irq);
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void __init spear_setup_timer(void)
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struct clk *pll3_clk;
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if (!request_mem_region(SPEAR_GPT0_BASE, SZ_1K, "gpt0")) {
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pr_err("%s:cannot get IO addr\n", __func__);
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gpt_base = (void __iomem *)ioremap(SPEAR_GPT0_BASE, SZ_1K);
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pr_err("%s:ioremap failed for gpt\n", __func__);
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gpt_clk = clk_get_sys("gpt0", NULL);
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pr_err("%s:couldn't get clk for gpt\n", __func__);
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pll3_clk = clk_get(NULL, "pll3_48m_clk");
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pr_err("%s:couldn't get PLL3 as parent for gpt\n", __func__);
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clk_set_parent(gpt_clk, pll3_clk);
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spear_clockevent_init();
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spear_clocksource_init();
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release_mem_region(SPEAR_GPT0_BASE, SZ_1K);
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struct sys_timer spear_sys_timer = {
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.init = spear_setup_timer,