2 * CS5536 General timer functions
4 * Copyright (C) 2007 Lemote Inc. & Insititute of Computing Technology
5 * Author: Yanhua, yanh@lemote.com
7 * Copyright (C) 2009 Lemote Inc.
8 * Author: Wu zhangjin, wuzhangjin@gmail.com
10 * Reference: AMD Geode(TM) CS5536 Companion Device Data Book
12 * This program is free software; you can redistribute it and/or modify it
13 * under the terms of the GNU General Public License as published by the
14 * Free Software Foundation; either version 2 of the License, or (at your
15 * option) any later version.
19 #include <linux/init.h>
20 #include <linux/module.h>
21 #include <linux/jiffies.h>
22 #include <linux/spinlock.h>
23 #include <linux/interrupt.h>
24 #include <linux/clockchips.h>
28 #include <cs5536/cs5536_mfgpt.h>
30 static DEFINE_RAW_SPINLOCK(mfgpt_lock);
32 static u32 mfgpt_base;
35 * Initialize the MFGPT timer.
37 * This is also called after resume to bring the MFGPT into operation again.
41 void disable_mfgpt0_counter(void)
43 outw(inw(MFGPT0_SETUP) & 0x7fff, MFGPT0_SETUP);
45 EXPORT_SYMBOL(disable_mfgpt0_counter);
47 /* enable counter, comparator2 to event mode, 14.318MHz clock */
48 void enable_mfgpt0_counter(void)
50 outw(0xe310, MFGPT0_SETUP);
52 EXPORT_SYMBOL(enable_mfgpt0_counter);
54 static void init_mfgpt_timer(enum clock_event_mode mode,
55 struct clock_event_device *evt)
57 raw_spin_lock(&mfgpt_lock);
60 case CLOCK_EVT_MODE_PERIODIC:
61 outw(COMPARE, MFGPT0_CMP2); /* set comparator2 */
62 outw(0, MFGPT0_CNT); /* set counter to 0 */
63 enable_mfgpt0_counter();
66 case CLOCK_EVT_MODE_SHUTDOWN:
67 case CLOCK_EVT_MODE_UNUSED:
68 if (evt->mode == CLOCK_EVT_MODE_PERIODIC ||
69 evt->mode == CLOCK_EVT_MODE_ONESHOT)
70 disable_mfgpt0_counter();
73 case CLOCK_EVT_MODE_ONESHOT:
74 /* The oneshot mode have very high deviation, Not use it! */
77 case CLOCK_EVT_MODE_RESUME:
78 /* Nothing to do here */
81 raw_spin_unlock(&mfgpt_lock);
84 static struct clock_event_device mfgpt_clockevent = {
86 .features = CLOCK_EVT_FEAT_PERIODIC,
87 .set_mode = init_mfgpt_timer,
88 .irq = CS5536_MFGPT_INTR,
91 static irqreturn_t timer_interrupt(int irq, void *dev_id)
96 * get MFGPT base address
98 * NOTE: do not remove me, it's need for the value of mfgpt_base is
101 _rdmsr(DIVIL_MSR_REG(DIVIL_LBAR_MFGPT), &basehi, &mfgpt_base);
104 outw(inw(MFGPT0_SETUP) | 0x4000, MFGPT0_SETUP);
106 mfgpt_clockevent.event_handler(&mfgpt_clockevent);
111 static struct irqaction irq5 = {
112 .handler = timer_interrupt,
113 .flags = IRQF_NOBALANCING | IRQF_TIMER,
118 * Initialize the conversion factor and the min/max deltas of the clock event
119 * structure and register the clock event source with the framework.
121 void __init setup_mfgpt0_timer(void)
124 struct clock_event_device *cd = &mfgpt_clockevent;
125 unsigned int cpu = smp_processor_id();
127 cd->cpumask = cpumask_of(cpu);
128 clockevent_set_clock(cd, MFGPT_TICK_RATE);
129 cd->max_delta_ns = clockevent_delta2ns(0xffff, cd);
130 cd->min_delta_ns = clockevent_delta2ns(0xf, cd);
132 /* Enable MFGPT0 Comparator 2 Output to the Interrupt Mapper */
133 _wrmsr(DIVIL_MSR_REG(MFGPT_IRQ), 0, 0x100);
135 /* Enable Interrupt Gate 5 */
136 _wrmsr(DIVIL_MSR_REG(PIC_ZSEL_LOW), 0, 0x50000);
138 /* get MFGPT base address */
139 _rdmsr(DIVIL_MSR_REG(DIVIL_LBAR_MFGPT), &basehi, &mfgpt_base);
141 clockevents_register_device(cd);
143 setup_irq(CS5536_MFGPT_INTR, &irq5);
147 * Since the MFGPT overflows every tick, its not very useful
148 * to just read by itself. So use jiffies to emulate a free
151 static cycle_t mfgpt_read(struct clocksource *cs)
156 static int old_count;
159 raw_spin_lock_irqsave(&mfgpt_lock, flags);
161 * Although our caller may have the read side of xtime_lock,
162 * this is now a seqlock, and we are cheating in this routine
163 * by having side effects on state that we cannot undo if
164 * there is a collision on the seqlock and our caller has to
165 * retry. (Namely, old_jifs and old_count.) So we must treat
166 * jiffies as volatile despite the lock. We read jiffies
167 * before latching the timer count to guarantee that although
168 * the jiffies value might be older than the count (that is,
169 * the counter may underflow between the last point where
170 * jiffies was incremented and the point where we latch the
171 * count), it cannot be newer.
175 count = inw(MFGPT0_CNT);
178 * It's possible for count to appear to go the wrong way for this
181 * The timer counter underflows, but we haven't handled the resulting
182 * interrupt and incremented jiffies yet.
184 * Previous attempts to handle these cases intelligently were buggy, so
185 * we just do the simple thing now.
187 if (count < old_count && jifs == old_jifs)
193 raw_spin_unlock_irqrestore(&mfgpt_lock, flags);
195 return (cycle_t) (jifs * COMPARE) + count;
198 static struct clocksource clocksource_mfgpt = {
200 .rating = 120, /* Functional for real use, but not desired */
202 .mask = CLOCKSOURCE_MASK(32),
205 int __init init_mfgpt_clocksource(void)
207 if (num_possible_cpus() > 1) /* MFGPT does not scale! */
210 return clocksource_register_hz(&clocksource_mfgpt, MFGPT_TICK_RATE);
213 arch_initcall(init_mfgpt_clocksource);