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(ticks: 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: IRQ_TIMER0, handler: ioc_timer_interrupt, flags: 0, name: "timer" , NULL)) |
96 | pr_err("Failed to request irq %d (timer)\n" , IRQ_TIMER0); |
97 | } |
98 | |