u-boot/arch/arm/cpu/arm920t/ep93xx/speed.c

/*
 * Cirrus Logic EP93xx PLL support.
 *
 * Copyright (C) 2009 Matthias Kaehlcke <matthias@kaehlcke.net>
 *
 * SPDX-License-Identifier:	GPL-2.0+
 */

#include <common.h>
#include <asm/arch/ep93xx.h>
#include <asm/io.h>
#include <div64.h>

/*
 * CONFIG_SYS_CLK_FREQ should be defined as the input frequency of the PLL.
 *
 * get_FCLK(), get_HCLK(), get_PCLK() and get_UCLK() return the clock of
 * the specified bus in HZ.
 */

/*
 * return the PLL output frequency
 *
 * PLL rate = CONFIG_SYS_CLK_FREQ * (X1FBD + 1) * (X2FBD + 1)
 * / (X2IPD + 1) / 2^PS
 */
static ulong get_PLLCLK(uint32_t *pllreg)
{
	uint8_t i;
	const uint32_t clkset = readl(pllreg);
	uint64_t rate = CONFIG_SYS_CLK_FREQ;
	rate *= ((clkset >> SYSCON_CLKSET_PLL_X1FBD1_SHIFT) & 0x1f) + 1;
	rate *= ((clkset >> SYSCON_CLKSET_PLL_X2FBD2_SHIFT) & 0x3f) + 1;
	do_div(rate, (clkset  & 0x1f) + 1);			/* X2IPD */
	for (i = 0; i < ((clkset >> SYSCON_CLKSET_PLL_PS_SHIFT) & 3); i++)
		rate >>= 1;

	return (ulong)rate;
}

/* return FCLK frequency */
ulong get_FCLK(void)
{
	const uint8_t fclk_divisors[] = { 1, 2, 4, 8, 16, 1, 1, 1 };
	struct syscon_regs *syscon = (struct syscon_regs *)SYSCON_BASE;

	const uint32_t clkset1 = readl(&syscon->clkset1);
	const uint8_t fclk_div =
		fclk_divisors[(clkset1 >> SYSCON_CLKSET1_FCLK_DIV_SHIFT) & 7];
	const ulong fclk_rate = get_PLLCLK(&syscon->clkset1) / fclk_div;

	return fclk_rate;
}

/* return HCLK frequency */
ulong get_HCLK(void)
{
	const uint8_t hclk_divisors[] = { 1, 2, 4, 5, 6, 8, 16, 32 };
	struct syscon_regs *syscon = (struct syscon_regs *)SYSCON_BASE;

	const uint32_t clkset1 = readl(&syscon->clkset1);
	const uint8_t hclk_div =
		hclk_divisors[(clkset1 >> SYSCON_CLKSET1_HCLK_DIV_SHIFT) & 7];
	const ulong hclk_rate = get_PLLCLK(&syscon->clkset1) / hclk_div;

	return hclk_rate;
}

/* return PCLK frequency */
ulong get_PCLK(void)
{
	const uint8_t pclk_divisors[] = { 1, 2, 4, 8 };
	struct syscon_regs *syscon = (struct syscon_regs *)SYSCON_BASE;

	const uint32_t clkset1 = readl(&syscon->clkset1);
	const uint8_t pclk_div =
		pclk_divisors[(clkset1 >> SYSCON_CLKSET1_PCLK_DIV_SHIFT) & 3];
	const ulong pclk_rate = get_HCLK() / pclk_div;

	return pclk_rate;
}

/* return UCLK frequency */
ulong get_UCLK(void)
{
	struct syscon_regs *syscon = (struct syscon_regs *)SYSCON_BASE;
	ulong uclk_rate;

	const uint32_t value = readl(&syscon->pwrcnt);
	if (value & SYSCON_PWRCNT_UART_BAUD)
		uclk_rate = CONFIG_SYS_CLK_FREQ;
	else
		uclk_rate = CONFIG_SYS_CLK_FREQ / 2;

	return uclk_rate;
}