#include <libopencm3/stm32/rcc.h>
#include <libopencm3/stm32/flash.h>

static inline void rcc_clock_setup_in_hse_8mhz_out_48mhz(void)
{
	/* The part says SYSCLK < 36MHz, but to get usb we need */
 	/* sysclk == 48MHz or 72MHz */


	/* Enable internal high-speed oscillator. */
	rcc_osc_on(HSI);
	rcc_wait_for_osc_ready(HSI);

	/* Select HSI as SYSCLK source. */
	rcc_set_sysclk_source(RCC_CFGR_SW_SYSCLKSEL_HSICLK);

	/* Enable external high-speed oscillator 8MHz. */
	rcc_osc_on(HSE);
	rcc_wait_for_osc_ready(HSE);
	rcc_set_sysclk_source(RCC_CFGR_SW_SYSCLKSEL_HSECLK);

	/*
	 * Set prescalers for AHB, ADC, ABP1, ABP2.
	 * Do this before touching the PLL (TODO: why?).
	 */
	rcc_set_hpre(RCC_CFGR_HPRE_SYSCLK_DIV2);       /* Set. 24MHz Max. 36MHz */
	rcc_set_adcpre(RCC_CFGR_ADCPRE_PCLK2_DIV4);    /* Set. 12MHz Max. 14MHz */
	rcc_set_ppre1(RCC_CFGR_PPRE1_HCLK_NODIV);      /* Set. 24MHz Max. 36MHz */
	rcc_set_ppre2(RCC_CFGR_PPRE2_HCLK_NODIV);      /* Set. 24MHz Max. 36MHz */
	rcc_set_usbpre(RCC_CFGR_USBPRE_PLL_CLK_NODIV); /* Set. 48Mhz Max. 48Mhz */

	/*
	 * Sysclk runs with 36MHz -> 1 waitstates.
	 * 0WS from 0-24MHz
	 * 1WS from 24-48MHz
	 * 2WS from 48-72MHz
	 */
	flash_set_ws(FLASH_ACR_LATENCY_1WS);

	/*
	 * Set the PLL multiplication factor to 3.
	 * 8MHz (external) * 6 (multiplier) = 48MHz
	 */
	rcc_set_pll_multiplication_factor(RCC_CFGR_PLLMUL_PLL_CLK_MUL6);

	/* Select HSE as PLL source. */
	rcc_set_pll_source(RCC_CFGR_PLLSRC_HSE_CLK);

	/*
	 * Don't Divide external frequency by 2 before entering PLL
	 * (only valid/needed for HSE).
	 */
	rcc_set_pllxtpre(RCC_CFGR_PLLXTPRE_HSE_CLK);

	/* Enable PLL oscillator and wait for it to stabilize. */
	rcc_osc_on(PLL);
	rcc_wait_for_osc_ready(PLL);

	/* Select PLL as SYSCLK source. */
	rcc_set_sysclk_source(RCC_CFGR_SW_SYSCLKSEL_PLLCLK);

	/* Set the peripheral clock frequencies used */
	rcc_ahb_frequency = 24000000;
	rcc_apb1_frequency = 24000000;
	rcc_apb2_frequency = 24000000;
}