cpu/arm926ejs/at91/clock.c

/*
 * [origin: Linux kernel linux/arch/arm/mach-at91/clock.c]
 *
 * Copyright (C) 2005 David Brownell
 * Copyright (C) 2005 Ivan Kokshaysky
 * Copyright (C) 2009 Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 */

#include <config.h>
#include <asm/arch/hardware.h>
#include <asm/arch/at91_pmc.h>
#include <asm/arch/clk.h>
#include <asm/arch/io.h>

static unsigned long cpu_clk_rate_hz;
static unsigned long main_clk_rate_hz;
static unsigned long mck_rate_hz;
static unsigned long plla_rate_hz;
static unsigned long pllb_rate_hz;
static u32 at91_pllb_usb_init;

unsigned long get_cpu_clk_rate(void)
{
	return cpu_clk_rate_hz;
}

unsigned long get_main_clk_rate(void)
{
	return main_clk_rate_hz;
}

unsigned long get_mck_clk_rate(void)
{
	return mck_rate_hz;
}

unsigned long get_plla_clk_rate(void)
{
	return plla_rate_hz;
}

unsigned long get_pllb_clk_rate(void)
{
	return pllb_rate_hz;
}

u32 get_pllb_init(void)
{
	return at91_pllb_usb_init;
}

static unsigned long at91_css_to_rate(unsigned long css)
{
	switch (css) {
		case AT91_PMC_CSS_SLOW:
			return AT91_SLOW_CLOCK;
		case AT91_PMC_CSS_MAIN:
			return main_clk_rate_hz;
		case AT91_PMC_CSS_PLLA:
			return plla_rate_hz;
		case AT91_PMC_CSS_PLLB:
			return pllb_rate_hz;
	}

	return 0;
}

#ifdef CONFIG_USB_ATMEL
static unsigned at91_pll_calc(unsigned main_freq, unsigned out_freq)
{
	unsigned i, div = 0, mul = 0, diff = 1 << 30;
	unsigned ret = (out_freq > 155000000) ? 0xbe00 : 0x3e00;

	/* PLL output max 240 MHz (or 180 MHz per errata) */
	if (out_freq > 240000000)
		goto fail;

	for (i = 1; i < 256; i++) {
		int diff1;
		unsigned input, mul1;

		/*
		 * PLL input between 1MHz and 32MHz per spec, but lower
		 * frequences seem necessary in some cases so allow 100K.
		 * Warning: some newer products need 2MHz min.
		 */
		input = main_freq / i;
#if defined(CONFIG_AT91SAM9G20)
		if (input < 2000000)
			continue;
#endif
		if (input < 100000)
			continue;
		if (input > 32000000)
			continue;

		mul1 = out_freq / input;
#if defined(CONFIG_AT91SAM9G20)
		if (mul > 63)
			continue;
#endif
		if (mul1 > 2048)
			continue;
		if (mul1 < 2)
			goto fail;

		diff1 = out_freq - input * mul1;
		if (diff1 < 0)
			diff1 = -diff1;
		if (diff > diff1) {
			diff = diff1;
			div = i;
			mul = mul1;
			if (diff == 0)
				break;
		}
	}
	if (i == 256 && diff > (out_freq >> 5))
		goto fail;
	return ret | ((mul - 1) << 16) | div;
fail:
	return 0;
}
#endif

static u32 at91_pll_rate(u32 freq, u32 reg)
{
	unsigned mul, div;

	div = reg & 0xff;
	mul = (reg >> 16) & 0x7ff;
	if (div && mul) {
		freq /= div;
		freq *= mul + 1;
	} else
		freq = 0;

	return freq;
}

int at91_clock_init(unsigned long main_clock)
{
	unsigned freq, mckr;
#ifndef AT91_MAIN_CLOCK
	unsigned tmp;
	/*
	 * When the bootloader initialized the main oscillator correctly,
	 * there's no problem using the cycle counter.  But if it didn't,
	 * or when using oscillator bypass mode, we must be told the speed
	 * of the main clock.
	 */
	if (!main_clock) {
		do {
			tmp = at91_sys_read(AT91_CKGR_MCFR);
		} while (!(tmp & AT91_PMC_MAINRDY));
		main_clock = (tmp & AT91_PMC_MAINF) * (AT91_SLOW_CLOCK / 16);
	}
#endif
	main_clk_rate_hz = main_clock;

	/* report if PLLA is more than mildly overclocked */
	plla_rate_hz = at91_pll_rate(main_clock, at91_sys_read(AT91_CKGR_PLLAR));

#ifdef CONFIG_USB_ATMEL
	/*
	 * USB clock init:  choose 48 MHz PLLB value,
	 * disable 48MHz clock during usb peripheral suspend.
	 *
	 * REVISIT:  assumes MCK doesn't derive from PLLB!
	 */
	at91_pllb_usb_init = at91_pll_calc(main_clock, 48000000 * 2) |
			     AT91_PMC_USB96M;
	pllb_rate_hz = at91_pll_rate(main_clock, at91_pllb_usb_init);
#endif

	/*
	 * MCK and CPU derive from one of those primary clocks.
	 * For now, assume this parentage won't change.
	 */
	mckr = at91_sys_read(AT91_PMC_MCKR);
	freq = mck_rate_hz = at91_css_to_rate(mckr & AT91_PMC_CSS);
	freq /= (1 << ((mckr & AT91_PMC_PRES) >> 2));			/* prescale */
#if defined(CONFIG_AT91RM9200)
	mck_rate_hz = freq / (1 + ((mckr & AT91_PMC_MDIV) >> 8));	/* mdiv */
#elif defined(CONFIG_AT91SAM9G20)
	mck_rate_hz = (mckr & AT91_PMC_MDIV) ?
		freq / ((mckr & AT91_PMC_MDIV) >> 7) : freq;	/* mdiv ; (x >> 7) = ((x >> 8) * 2) */
	if (mckr & AT91_PMC_PDIV)
		freq /= 2;		/* processor clock division */
#else
	mck_rate_hz = freq / (1 << ((mckr & AT91_PMC_MDIV) >> 8));	/* mdiv */
#endif
	cpu_clk_rate_hz = freq;

		return 0;
}