rt-thread/libcpu/arm/at91sam926x/system_clock.c

/*
 * File      : clock.c
 * This file is part of RT-Thread RTOS
 * COPYRIGHT (C) 2006, RT-Thread Development Team
 *
 * The license and distribution terms for this file may be
 * found in the file LICENSE in this distribution or at
 * http://openlab.rt-thread.com/license/LICENSE
 *
 * Change Logs:
 * Date           Author       Notes
 * 2011-01-13     weety       first version
 */

#include <rtthread.h>
#include "at91sam926x.h"

static rt_list_t clocks;

struct clk {
	char name[32];
	rt_uint32_t rate_hz;
	struct clk *parent;
	rt_list_t  node;
};

static struct clk clk32k = {
	"clk32k",
	AT91_SLOW_CLOCK,
	RT_NULL,
	{RT_NULL, RT_NULL},
};

static struct clk main_clk = {
	"main",
	0,
	RT_NULL,
	{RT_NULL, RT_NULL},
};

static struct clk plla = {
	"plla",
	0,
	RT_NULL,
	{RT_NULL, RT_NULL},
};

static struct clk mck = {
	"mck",
	0,
	RT_NULL,
	{RT_NULL, RT_NULL},
};

static struct clk uhpck = {
	"uhpck",
	0,
	RT_NULL,
	{RT_NULL, RT_NULL},
};

static struct clk pllb = {
	"pllb",
	0,
	&main_clk,
	{RT_NULL, RT_NULL},
};

static struct clk udpck = {
	"udpck",
	0,
	&pllb,
	{RT_NULL, RT_NULL},
};

static struct clk *const standard_pmc_clocks[] = {
	/* four primary clocks */
	&clk32k,
	&main_clk,
	&plla,

	/* MCK */
	&mck
};

/* clocks cannot be de-registered no refcounting necessary */
struct clk *clk_get(const char *id)
{
	struct clk *clk;
	rt_list_t *list;
	
	for (list = (&clocks)->next; list != &clocks; list = list->next)
	{
		clk = (struct clk *)rt_list_entry(list, struct clk, node);
		if (rt_strcmp(id, clk->name) == 0)
			return clk;
	}

	return RT_NULL;
}

rt_uint32_t clk_get_rate(struct clk *clk)
{
	rt_uint32_t	flags;
	rt_uint32_t	rate;

	for (;;) {
		rate = clk->rate_hz;
		if (rate || !clk->parent)
			break;
		clk = clk->parent;
	}
	return rate;
}

static rt_uint32_t at91_pll_rate(struct clk *pll, rt_uint32_t freq, rt_uint32_t reg)
{
	unsigned mul, div;

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

	return freq;
}

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 (input < 100000)
			continue;
		if (input > 32000000)
			continue;

		mul1 = out_freq / input;
		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;
}

static rt_uint32_t at91_usb_rate(struct clk *pll, rt_uint32_t freq, rt_uint32_t reg)
{
	if (pll == &pllb && (reg & AT91_PMC_USB96M))
		return freq / 2;
	else
		return freq;
}


/* PLLB generated USB full speed clock init */
static void at91_pllb_usbfs_clock_init(rt_uint32_t main_clock)
{
	rt_uint32_t at91_pllb_usb_init;
	/*
	 * USB clock init:  choose 48 MHz PLLB value,
	 * disable 48MHz clock during usb peripheral suspend.
	 *
	 * REVISIT:  assumes MCK doesn't derive from PLLB!
	 */
	uhpck.parent = &pllb;

	at91_pllb_usb_init = at91_pll_calc(main_clock, 48000000 * 2) | AT91_PMC_USB96M;
	pllb.rate_hz = at91_pll_rate(&pllb, main_clock, at91_pllb_usb_init);
	
	at91_sys_write(AT91_CKGR_PLLBR, 0);

	udpck.rate_hz = at91_usb_rate(&pllb, pllb.rate_hz, at91_pllb_usb_init);
	uhpck.rate_hz = at91_usb_rate(&pllb, pllb.rate_hz, at91_pllb_usb_init);
}

static struct clk *at91_css_to_clk(unsigned long css)
{
	switch (css) {
		case AT91_PMC_CSS_SLOW:
			return &clk32k;
		case AT91_PMC_CSS_MAIN:
			return &main_clk;
		case AT91_PMC_CSS_PLLA:
			return &plla;
		case AT91_PMC_CSS_PLLB:
			return &pllb;
	}

	return RT_NULL;
}

#define false 0
#define true  1
int at91_clock_init(rt_uint32_t main_clock)
{
	unsigned tmp, freq, mckr;
	int i;
	int pll_overclock = false;

	/*
	 * 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);
	}
	main_clk.rate_hz = main_clock;

	/* report if PLLA is more than mildly overclocked */
	plla.rate_hz = at91_pll_rate(&plla, main_clock, at91_sys_read(AT91_CKGR_PLLAR));
	if (plla.rate_hz > 209000000)
		pll_overclock = true;
	if (pll_overclock)
		;//rt_kprintf("Clocks: PLLA overclocked, %ld MHz\n", plla.rate_hz / 1000000);

	at91_pllb_usbfs_clock_init(main_clock);

	/*
	 * 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);
	mck.parent = at91_css_to_clk(mckr & AT91_PMC_CSS);
	freq = mck.parent->rate_hz;
	freq /= (1 << ((mckr & AT91_PMC_PRES) >> 2));				/* prescale */
	
	mck.rate_hz = freq / (1 << ((mckr & AT91_PMC_MDIV) >> 8));      /* mdiv */

	/* Register the PMC's standard clocks */
	rt_list_init(&clocks);
	for (i = 0; i < ARRAY_SIZE(standard_pmc_clocks); i++)
		rt_list_insert_after(&clocks, &standard_pmc_clocks[i]->node);

	rt_list_insert_after(&clocks, &pllb.node);
	rt_list_insert_after(&clocks, &uhpck.node);
	rt_list_insert_after(&clocks, &udpck.node);

	/* MCK and CPU clock are "always on" */
	//clk_enable(&mck);

	/*rt_kprintf("Clocks: CPU %u MHz, master %u MHz, main %u.%03u MHz\n",
		freq / 1000000, (unsigned) mck.rate_hz / 1000000,
		(unsigned) main_clock / 1000000,
		((unsigned) main_clock % 1000000) / 1000);*///cause blocked

	return 0;
}

/**
 * @brief System Clock Configuration
 */
void rt_hw_clock_init(void)
{
	at91_clock_init(18432000);
}