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
27static u32 ioc_time;
28
29static 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
67static struct clocksource ioctime_clocksource = {
68	.read = ioc_timer_read,
69	.mask = CLOCKSOURCE_MASK(32),
70	.rating = 100,
71};
72
73void __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
80static irqreturn_t
81ioc_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 */
91void __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