[linux-2.6-block.git] / arch / mips / generic / board-ranchu.c

// 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,
};
Commit	Line	Data
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	};