| Andrew Scull | b4b6d4a | 2019-01-02 15:54:55 +0000 | [diff] [blame^] | 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 | |
| 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 | |
| 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 | }; |