u-boot/arch/arm/cpu/armv7/sunxi/clock_sun6i.c

/*
 * sun6i specific clock code
 *
 * (C) Copyright 2007-2012
 * Allwinner Technology Co., Ltd. <www.allwinnertech.com>
 * Tom Cubie <tangliang@allwinnertech.com>
 *
 * (C) Copyright 2013 Luke Kenneth Casson Leighton <lkcl@lkcl.net>
 *
 * SPDX-License-Identifier:	GPL-2.0+
 */

#include <common.h>
#include <asm/io.h>
#include <asm/arch/clock.h>
#include <asm/arch/sys_proto.h>

void clock_init_uart(void)
{
	struct sunxi_ccm_reg *const ccm =
		(struct sunxi_ccm_reg *)SUNXI_CCM_BASE;

	/* uart clock source is apb2 */
	writel(APB2_CLK_SRC_OSC24M|
	       APB2_CLK_RATE_N_1|
	       APB2_CLK_RATE_M(1),
	       &ccm->apb2_div);

	/* open the clock for uart */
	setbits_le32(&ccm->apb2_gate,
		     CLK_GATE_OPEN << (APB2_GATE_UART_SHIFT +
				       CONFIG_CONS_INDEX - 1));

	/* deassert uart reset */
	setbits_le32(&ccm->apb2_reset_cfg,
		     1 << (APB2_RESET_UART_SHIFT +
			   CONFIG_CONS_INDEX - 1));

	/* Dup with clock_init_safe(), drop once sun6i SPL support lands */
	writel(PLL6_CFG_DEFAULT, &ccm->pll6_cfg);
}

int clock_twi_onoff(int port, int state)
{
	struct sunxi_ccm_reg *const ccm =
		(struct sunxi_ccm_reg *)SUNXI_CCM_BASE;

	if (port > 3)
		return -1;

	/* set the apb clock gate for twi */
	if (state)
		setbits_le32(&ccm->apb2_gate,
			     CLK_GATE_OPEN << (APB2_GATE_TWI_SHIFT+port));
	else
		clrbits_le32(&ccm->apb2_gate,
			     CLK_GATE_OPEN << (APB2_GATE_TWI_SHIFT+port));

	return 0;
}

unsigned int clock_get_pll6(void)
{
	struct sunxi_ccm_reg *const ccm =
		(struct sunxi_ccm_reg *)SUNXI_CCM_BASE;
	uint32_t rval = readl(&ccm->pll6_cfg);
	int n = ((rval & CCM_PLL6_CTRL_N_MASK) >> CCM_PLL6_CTRL_N_SHIFT) + 1;
	int k = ((rval & CCM_PLL6_CTRL_K_MASK) >> CCM_PLL6_CTRL_K_SHIFT) + 1;
	return 24000000 * n * k / 2;
}