1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * linux/arch/arm/common/time-acorn.c
4 *
5 * Copyright (c) 1996-2000 Russell King.
6 *
7 * Changelog:
8 * 24-Sep-1996 RMK Created
9 * 10-Oct-1996 RMK Brought up to date with arch-sa110eval
10 * 04-Dec-1997 RMK Updated for new arch/arm/time.c
11 * 13=Jun-2004 DS Moved to arch/arm/common b/c shared w/CLPS7500
12 */
13 #include <linux/clocksource.h>
14 #include <linux/init.h>
15 #include <linux/interrupt.h>
16 #include <linux/irq.h>
17 #include <linux/io.h>
18
19 #include <mach/hardware.h>
20 #include <asm/hardware/ioc.h>
21
22 #include <asm/mach/time.h>
23
24 #define RPC_CLOCK_FREQ 2000000
25 #define RPC_LATCH DIV_ROUND_CLOSEST(RPC_CLOCK_FREQ, HZ)
26
27 static u32 ioc_time;
28
29 static u64 ioc_timer_read(struct clocksource *cs)
30 {
31 unsigned int count1, count2, status;
32 unsigned long flags;
33 u32 ticks;
34
35 local_irq_save(flags);
36 ioc_writeb (0, IOC_T0LATCH);
37 barrier ();
38 count1 = ioc_readb(IOC_T0CNTL) | (ioc_readb(IOC_T0CNTH) << 8);
39 barrier ();
40 status = ioc_readb(IOC_IRQREQA);
41 barrier ();
42 ioc_writeb (0, IOC_T0LATCH);
43 barrier ();
44 count2 = ioc_readb(IOC_T0CNTL) | (ioc_readb(IOC_T0CNTH) << 8);
45 ticks = ioc_time + RPC_LATCH - count2;
46 local_irq_restore(flags);
47
48 if (count2 < count1) {
49 /*
50 * The timer has not reloaded between reading count1 and
51 * count2, check whether an interrupt was actually pending.
52 */
53 if (status & (1 << 5))
54 ticks += RPC_LATCH;
55 } else if (count2 > count1) {
56 /*
57 * The timer has reloaded, so count2 indicates the new
58 * count since the wrap. The interrupt would not have
59 * been processed, so add the missed ticks.
60 */
61 ticks += RPC_LATCH;
62 }
63
64 return ticks;
65 }
66
67 static struct clocksource ioctime_clocksource = {
68 .read = ioc_timer_read,
69 .mask = CLOCKSOURCE_MASK(32),
70 .rating = 100,
71 };
72
73 void __init ioctime_init(void)
74 {
75 ioc_writeb(RPC_LATCH & 255, IOC_T0LTCHL);
76 ioc_writeb(RPC_LATCH >> 8, IOC_T0LTCHH);
77 ioc_writeb(0, IOC_T0GO);
78 }
79
80 static irqreturn_t
81 ioc_timer_interrupt(int irq, void *dev_id)
82 {
83 ioc_time += RPC_LATCH;
84 legacy_timer_tick(1);
85 return IRQ_HANDLED;
86 }
87
88 /*
89 * Set up timer interrupt.
90 */
91 void __init ioc_timer_init(void)
92 {
93 WARN_ON(clocksource_register_hz(&ioctime_clocksource, RPC_CLOCK_FREQ));
94 ioctime_init();
95 if (request_irq(IRQ_TIMER0, ioc_timer_interrupt, 0, "timer", NULL))
96 pr_err("Failed to request irq %d (timer)\n", IRQ_TIMER0);
97 }
98
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