1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * CS5536 General timer functions
4 *
5 * Copyright (C) 2007 Lemote Inc. & Institute of Computing Technology
6 * Author: Yanhua, yanh@lemote.com
7 *
8 * Copyright (C) 2009 Lemote Inc.
9 * Author: Wu zhangjin, wuzhangjin@gmail.com
10 *
11 * Reference: AMD Geode(TM) CS5536 Companion Device Data Book
12 */
13
14 #include <linux/io.h>
15 #include <linux/init.h>
16 #include <linux/export.h>
17 #include <linux/jiffies.h>
18 #include <linux/spinlock.h>
19 #include <linux/interrupt.h>
20 #include <linux/clockchips.h>
21
22 #include <asm/time.h>
23
24 #include <cs5536/cs5536_mfgpt.h>
25
26 static DEFINE_RAW_SPINLOCK(mfgpt_lock);
27
28 static u32 mfgpt_base;
29
30 /*
31 * Initialize the MFGPT timer.
32 *
33 * This is also called after resume to bring the MFGPT into operation again.
34 */
35
36 /* disable counter */
37 void disable_mfgpt0_counter(void)
38 {
39 outw(inw(MFGPT0_SETUP) & 0x7fff, MFGPT0_SETUP);
40 }
41 EXPORT_SYMBOL(disable_mfgpt0_counter);
42
43 /* enable counter, comparator2 to event mode, 14.318MHz clock */
44 void enable_mfgpt0_counter(void)
45 {
46 outw(0xe310, MFGPT0_SETUP);
47 }
48 EXPORT_SYMBOL(enable_mfgpt0_counter);
49
50 static int mfgpt_timer_set_periodic(struct clock_event_device *evt)
51 {
52 raw_spin_lock(&mfgpt_lock);
53
54 outw(COMPARE, MFGPT0_CMP2); /* set comparator2 */
55 outw(0, MFGPT0_CNT); /* set counter to 0 */
56 enable_mfgpt0_counter();
57
58 raw_spin_unlock(&mfgpt_lock);
59 return 0;
60 }
61
62 static int mfgpt_timer_shutdown(struct clock_event_device *evt)
63 {
64 if (clockevent_state_periodic(evt) || clockevent_state_oneshot(evt)) {
65 raw_spin_lock(&mfgpt_lock);
66 disable_mfgpt0_counter();
67 raw_spin_unlock(&mfgpt_lock);
68 }
69
70 return 0;
71 }
72
73 static struct clock_event_device mfgpt_clockevent = {
74 .name = "mfgpt",
75 .features = CLOCK_EVT_FEAT_PERIODIC,
76
77 /* The oneshot mode have very high deviation, don't use it! */
78 .set_state_shutdown = mfgpt_timer_shutdown,
79 .set_state_periodic = mfgpt_timer_set_periodic,
80 .irq = CS5536_MFGPT_INTR,
81 };
82
83 static irqreturn_t timer_interrupt(int irq, void *dev_id)
84 {
85 u32 basehi;
86
87 /*
88 * get MFGPT base address
89 *
90 * NOTE: do not remove me, it's need for the value of mfgpt_base is
91 * variable
92 */
93 _rdmsr(DIVIL_MSR_REG(DIVIL_LBAR_MFGPT), &basehi, &mfgpt_base);
94
95 /* ack */
96 outw(inw(MFGPT0_SETUP) | 0x4000, MFGPT0_SETUP);
97
98 mfgpt_clockevent.event_handler(&mfgpt_clockevent);
99
100 return IRQ_HANDLED;
101 }
102
103 /*
104 * Initialize the conversion factor and the min/max deltas of the clock event
105 * structure and register the clock event source with the framework.
106 */
107 void __init setup_mfgpt0_timer(void)
108 {
109 u32 basehi;
110 struct clock_event_device *cd = &mfgpt_clockevent;
111 unsigned int cpu = smp_processor_id();
112
113 cd->cpumask = cpumask_of(cpu);
114 clockevent_set_clock(cd, MFGPT_TICK_RATE);
115 cd->max_delta_ns = clockevent_delta2ns(0xffff, cd);
116 cd->max_delta_ticks = 0xffff;
117 cd->min_delta_ns = clockevent_delta2ns(0xf, cd);
118 cd->min_delta_ticks = 0xf;
119
120 /* Enable MFGPT0 Comparator 2 Output to the Interrupt Mapper */
121 _wrmsr(DIVIL_MSR_REG(MFGPT_IRQ), 0, 0x100);
122
123 /* Enable Interrupt Gate 5 */
124 _wrmsr(DIVIL_MSR_REG(PIC_ZSEL_LOW), 0, 0x50000);
125
126 /* get MFGPT base address */
127 _rdmsr(DIVIL_MSR_REG(DIVIL_LBAR_MFGPT), &basehi, &mfgpt_base);
128
129 clockevents_register_device(cd);
130
131 if (request_irq(CS5536_MFGPT_INTR, timer_interrupt,
132 IRQF_NOBALANCING | IRQF_TIMER, "timer", NULL))
133 pr_err("Failed to register timer interrupt\n");
134 }
135
136 /*
137 * Since the MFGPT overflows every tick, its not very useful
138 * to just read by itself. So use jiffies to emulate a free
139 * running counter:
140 */
141 static u64 mfgpt_read(struct clocksource *cs)
142 {
143 unsigned long flags;
144 int count;
145 u32 jifs;
146 static int old_count;
147 static u32 old_jifs;
148
149 raw_spin_lock_irqsave(&mfgpt_lock, flags);
150 /*
151 * Although our caller may have the read side of xtime_lock,
152 * this is now a seqlock, and we are cheating in this routine
153 * by having side effects on state that we cannot undo if
154 * there is a collision on the seqlock and our caller has to
155 * retry. (Namely, old_jifs and old_count.) So we must treat
156 * jiffies as volatile despite the lock. We read jiffies
157 * before latching the timer count to guarantee that although
158 * the jiffies value might be older than the count (that is,
159 * the counter may underflow between the last point where
160 * jiffies was incremented and the point where we latch the
161 * count), it cannot be newer.
162 */
163 jifs = jiffies;
164 /* read the count */
165 count = inw(MFGPT0_CNT);
166
167 /*
168 * It's possible for count to appear to go the wrong way for this
169 * reason:
170 *
171 * The timer counter underflows, but we haven't handled the resulting
172 * interrupt and incremented jiffies yet.
173 *
174 * Previous attempts to handle these cases intelligently were buggy, so
175 * we just do the simple thing now.
176 */
177 if (count < old_count && jifs == old_jifs)
178 count = old_count;
179
180 old_count = count;
181 old_jifs = jifs;
182
183 raw_spin_unlock_irqrestore(&mfgpt_lock, flags);
184
185 return (u64) (jifs * COMPARE) + count;
186 }
187
188 static struct clocksource clocksource_mfgpt = {
189 .name = "mfgpt",
190 .rating = 120, /* Functional for real use, but not desired */
191 .read = mfgpt_read,
192 .mask = CLOCKSOURCE_MASK(32),
193 };
194
195 int __init init_mfgpt_clocksource(void)
196 {
197 if (num_possible_cpus() > 1) /* MFGPT does not scale! */
198 return 0;
199
200 return clocksource_register_hz(&clocksource_mfgpt, MFGPT_TICK_RATE);
201 }
202
203 arch_initcall(init_mfgpt_clocksource);
204
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