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2874c5fd | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
f2d0b0d5 MD |
2 | /* |
3 | * Support code for virtual Ranchu board for MIPS. | |
4 | * | |
5 | * Author: Miodrag Dinic <miodrag.dinic@mips.com> | |
f2d0b0d5 MD |
6 | */ |
7 | ||
8 | #include <linux/of_address.h> | |
9 | #include <linux/types.h> | |
10 | ||
11 | #include <asm/machine.h> | |
12 | #include <asm/mipsregs.h> | |
13 | #include <asm/time.h> | |
14 | ||
15 | #define GOLDFISH_TIMER_LOW 0x00 | |
16 | #define GOLDFISH_TIMER_HIGH 0x04 | |
17 | ||
18 | static __init u64 read_rtc_time(void __iomem *base) | |
19 | { | |
20 | u32 time_low; | |
21 | u32 time_high; | |
22 | ||
23 | /* | |
24 | * Reading the low address latches the high value | |
25 | * as well so there is no fear that we may read | |
26 | * inaccurate high value. | |
27 | */ | |
28 | time_low = readl(base + GOLDFISH_TIMER_LOW); | |
29 | time_high = readl(base + GOLDFISH_TIMER_HIGH); | |
30 | ||
31 | return ((u64)time_high << 32) | time_low; | |
32 | } | |
33 | ||
34 | static __init unsigned int ranchu_measure_hpt_freq(void) | |
35 | { | |
36 | u64 rtc_start, rtc_current, rtc_delta; | |
37 | unsigned int start, count; | |
38 | struct device_node *np; | |
39 | void __iomem *rtc_base; | |
40 | ||
41 | np = of_find_compatible_node(NULL, NULL, "google,goldfish-rtc"); | |
42 | if (!np) | |
43 | panic("%s(): Failed to find 'google,goldfish-rtc' dt node!", | |
44 | __func__); | |
45 | ||
46 | rtc_base = of_iomap(np, 0); | |
47 | if (!rtc_base) | |
48 | panic("%s(): Failed to ioremap Goldfish RTC base!", __func__); | |
49 | ||
50 | /* | |
51 | * Poll the nanosecond resolution RTC for one | |
52 | * second to calibrate the CPU frequency. | |
53 | */ | |
54 | rtc_start = read_rtc_time(rtc_base); | |
55 | start = read_c0_count(); | |
56 | ||
57 | do { | |
58 | rtc_current = read_rtc_time(rtc_base); | |
59 | rtc_delta = rtc_current - rtc_start; | |
60 | } while (rtc_delta < NSEC_PER_SEC); | |
61 | ||
62 | count = read_c0_count() - start; | |
63 | ||
64 | /* | |
65 | * Make sure the frequency will be a round number. | |
66 | * Without this correction, the returned value may vary | |
67 | * between subsequent emulation executions. | |
68 | * | |
69 | * TODO: Set this value using device tree. | |
70 | */ | |
71 | count += 5000; | |
72 | count -= count % 10000; | |
73 | ||
74 | iounmap(rtc_base); | |
75 | ||
76 | return count; | |
77 | } | |
78 | ||
79 | static const struct of_device_id ranchu_of_match[] __initconst = { | |
80 | { | |
81 | .compatible = "mti,ranchu", | |
82 | }, | |
e17ae5cd | 83 | {} |
f2d0b0d5 MD |
84 | }; |
85 | ||
86 | MIPS_MACHINE(ranchu) = { | |
87 | .matches = ranchu_of_match, | |
88 | .measure_hpt_freq = ranchu_measure_hpt_freq, | |
89 | }; |