91 lines
2.0 KiB
C
91 lines
2.0 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Support code for virtual Ranchu board for MIPS.
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*
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* Author: Miodrag Dinic <miodrag.dinic@mips.com>
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*/
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#include <linux/of_address.h>
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#include <linux/types.h>
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#include <asm/machine.h>
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#include <asm/mipsregs.h>
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#include <asm/time.h>
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#define GOLDFISH_TIMER_LOW 0x00
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#define GOLDFISH_TIMER_HIGH 0x04
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static __init u64 read_rtc_time(void __iomem *base)
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{
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u32 time_low;
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u32 time_high;
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/*
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* Reading the low address latches the high value
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* as well so there is no fear that we may read
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* inaccurate high value.
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*/
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time_low = readl(base + GOLDFISH_TIMER_LOW);
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time_high = readl(base + GOLDFISH_TIMER_HIGH);
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return ((u64)time_high << 32) | time_low;
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}
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static __init unsigned int ranchu_measure_hpt_freq(void)
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{
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u64 rtc_start, rtc_current, rtc_delta;
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unsigned int start, count;
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struct device_node *np;
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void __iomem *rtc_base;
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np = of_find_compatible_node(NULL, NULL, "google,goldfish-rtc");
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if (!np)
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panic("%s(): Failed to find 'google,goldfish-rtc' dt node!",
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__func__);
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rtc_base = of_iomap(np, 0);
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of_node_put(np);
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if (!rtc_base)
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panic("%s(): Failed to ioremap Goldfish RTC base!", __func__);
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/*
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* Poll the nanosecond resolution RTC for one
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* second to calibrate the CPU frequency.
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*/
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rtc_start = read_rtc_time(rtc_base);
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start = read_c0_count();
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do {
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rtc_current = read_rtc_time(rtc_base);
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rtc_delta = rtc_current - rtc_start;
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} while (rtc_delta < NSEC_PER_SEC);
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count = read_c0_count() - start;
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/*
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* Make sure the frequency will be a round number.
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* Without this correction, the returned value may vary
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* between subsequent emulation executions.
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*
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* TODO: Set this value using device tree.
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*/
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count += 5000;
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count -= count % 10000;
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iounmap(rtc_base);
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return count;
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}
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static const struct of_device_id ranchu_of_match[] __initconst = {
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{
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.compatible = "mti,ranchu",
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},
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{}
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};
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MIPS_MACHINE(ranchu) = {
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.matches = ranchu_of_match,
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.measure_hpt_freq = ranchu_measure_hpt_freq,
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};
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