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