1 /*
2 * Support code for virtual Ranchu board for MIPS.
3 *
4 * Author: Miodrag Dinic <miodrag.dinic@mips.com>
5 *
6 * This program is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License as published by the
8 * Free Software Foundation; either version 2 of the License, or (at your
9 * option) any later version.
10 */
11
12 #include <linux/of_address.h>
13 #include <linux/types.h>
14
15 #include <asm/machine.h>
16 #include <asm/mipsregs.h>
17 #include <asm/time.h>
18
19 #define GOLDFISH_TIMER_LOW 0x00
20 #define GOLDFISH_TIMER_HIGH 0x04
21
read_rtc_time(void __iomem * base)22 static __init u64 read_rtc_time(void __iomem *base)
23 {
24 u32 time_low;
25 u32 time_high;
26
27 /*
28 * Reading the low address latches the high value
29 * as well so there is no fear that we may read
30 * inaccurate high value.
31 */
32 time_low = readl(base + GOLDFISH_TIMER_LOW);
33 time_high = readl(base + GOLDFISH_TIMER_HIGH);
34
35 return ((u64)time_high << 32) | time_low;
36 }
37
ranchu_measure_hpt_freq(void)38 static __init unsigned int ranchu_measure_hpt_freq(void)
39 {
40 u64 rtc_start, rtc_current, rtc_delta;
41 unsigned int start, count;
42 struct device_node *np;
43 void __iomem *rtc_base;
44
45 np = of_find_compatible_node(NULL, NULL, "google,goldfish-rtc");
46 if (!np)
47 panic("%s(): Failed to find 'google,goldfish-rtc' dt node!",
48 __func__);
49
50 rtc_base = of_iomap(np, 0);
51 if (!rtc_base)
52 panic("%s(): Failed to ioremap Goldfish RTC base!", __func__);
53
54 /*
55 * Poll the nanosecond resolution RTC for one
56 * second to calibrate the CPU frequency.
57 */
58 rtc_start = read_rtc_time(rtc_base);
59 start = read_c0_count();
60
61 do {
62 rtc_current = read_rtc_time(rtc_base);
63 rtc_delta = rtc_current - rtc_start;
64 } while (rtc_delta < NSEC_PER_SEC);
65
66 count = read_c0_count() - start;
67
68 /*
69 * Make sure the frequency will be a round number.
70 * Without this correction, the returned value may vary
71 * between subsequent emulation executions.
72 *
73 * TODO: Set this value using device tree.
74 */
75 count += 5000;
76 count -= count % 10000;
77
78 iounmap(rtc_base);
79
80 return count;
81 }
82
83 static const struct of_device_id ranchu_of_match[] __initconst = {
84 {
85 .compatible = "mti,ranchu",
86 },
87 {}
88 };
89
90 MIPS_MACHINE(ranchu) = {
91 .matches = ranchu_of_match,
92 .measure_hpt_freq = ranchu_measure_hpt_freq,
93 };
94
