embassy/embassy-rp/src/clocks.rs

use pac::clocks::vals::*;

use crate::{pac, reset};

const XOSC_MHZ: u32 = 12;

/// safety: must be called exactly once at bootup
pub(crate) unsafe fn init() {
    // Reset everything except:
    // - QSPI (we're using it to run this code!)
    // - PLLs (it may be suicide if that's what's clocking us)
    // - USB, SYSCFG (breaks usb-to-swd on core1)
    let mut peris = reset::ALL_PERIPHERALS;
    peris.set_io_qspi(false);
    peris.set_pads_qspi(false);
    peris.set_pll_sys(false);
    peris.set_pll_usb(false);
    peris.set_usbctrl(false);
    peris.set_syscfg(false);
    reset::reset(peris);

    // Remove reset from peripherals which are clocked only by clk_sys and
    // clk_ref. Other peripherals stay in reset until we've configured clocks.
    let mut peris = reset::ALL_PERIPHERALS;
    peris.set_adc(false);
    peris.set_rtc(false);
    peris.set_spi0(false);
    peris.set_spi1(false);
    peris.set_uart0(false);
    peris.set_uart1(false);
    peris.set_usbctrl(false);
    reset::unreset_wait(peris);

    // Start tick in watchdog
    // xosc 12 mhz
    pac::WATCHDOG.tick().write(|w| {
        w.set_cycles(XOSC_MHZ as u16);
        w.set_enable(true);
    });

    // Disable resus that may be enabled from previous software
    let c = pac::CLOCKS;
    c.clk_sys_resus_ctrl()
        .write_value(pac::clocks::regs::ClkSysResusCtrl(0));

    // start XOSC
    start_xosc();

    // Before we touch PLLs, switch sys and ref cleanly away from their aux sources.
    c.clk_sys_ctrl().modify(|w| w.set_src(ClkSysCtrlSrc::CLK_REF));
    while c.clk_sys_selected().read() != 1 {}
    c.clk_ref_ctrl().modify(|w| w.set_src(ClkRefCtrlSrc::ROSC_CLKSRC_PH));
    while c.clk_ref_selected().read() != 1 {}

    // Configure PLLs
    //                   REF     FBDIV VCO            POSTDIV
    // PLL SYS: 12 / 1 = 12MHz * 125 = 1500MHZ / 6 / 2 = 125MHz
    // PLL USB: 12 / 1 = 12MHz * 40  = 480 MHz / 5 / 2 =  48MHz
    configure_pll(pac::PLL_SYS, 1, 1500_000_000, 6, 2);
    configure_pll(pac::PLL_USB, 1, 480_000_000, 5, 2);

    // CLK_REF = XOSC (12MHz) / 1 = 12MHz2Mhz
    c.clk_ref_ctrl().write(|w| {
        w.set_src(ClkRefCtrlSrc::XOSC_CLKSRC);
    });
    while c.clk_ref_selected().read() != 1 << ClkRefCtrlSrc::XOSC_CLKSRC.0 {}
    c.clk_ref_div().write(|w| w.set_int(1));

    // CLK SYS = PLL SYS (125MHz) / 1 = 125MHz
    c.clk_sys_ctrl().write(|w| {
        w.set_src(ClkSysCtrlSrc::CLK_REF);
    });
    while c.clk_sys_selected().read() != 1 << ClkSysCtrlSrc::CLK_REF.0 {}
    c.clk_sys_div().write(|w| w.set_int(1));
    c.clk_sys_ctrl().write(|w| {
        w.set_auxsrc(ClkSysCtrlAuxsrc::CLKSRC_PLL_SYS);
        w.set_src(ClkSysCtrlSrc::CLKSRC_CLK_SYS_AUX);
    });
    while c.clk_sys_selected().read() != 1 << ClkSysCtrlSrc::CLKSRC_CLK_SYS_AUX.0 {}

    // CLK USB = PLL USB (48MHz) / 1 = 48MHz
    c.clk_usb_div().write(|w| w.set_int(1));
    c.clk_usb_ctrl().write(|w| {
        w.set_enable(true);
        w.set_auxsrc(ClkUsbCtrlAuxsrc::CLKSRC_PLL_USB);
    });

    // CLK ADC = PLL USB (48MHZ) / 1 = 48MHz
    c.clk_adc_div().write(|w| w.set_int(1));
    c.clk_adc_ctrl().write(|w| {
        w.set_enable(true);
        w.set_auxsrc(ClkAdcCtrlAuxsrc::CLKSRC_PLL_USB);
    });

    // CLK RTC = PLL USB (48MHz) / 1024 = 46875Hz
    c.clk_rtc_ctrl().modify(|w| {
        w.set_enable(false);
    });
    c.clk_rtc_div().write(|w| w.set_int(1024));
    c.clk_rtc_ctrl().write(|w| {
        w.set_enable(true);
        w.set_auxsrc(ClkRtcCtrlAuxsrc::CLKSRC_PLL_USB);
    });

    // CLK PERI = clk_sys. Used as reference clock for Peripherals. No dividers so just select and enable
    // Normally choose clk_sys or clk_usb
    c.clk_peri_ctrl().write(|w| {
        w.set_enable(true);
        w.set_auxsrc(ClkPeriCtrlAuxsrc::CLK_SYS);
    });

    // Peripheral clocks should now all be running
    let peris = reset::ALL_PERIPHERALS;
    reset::unreset_wait(peris);
}

pub(crate) fn _clk_sys_freq() -> u32 {
    125_000_000
}

pub(crate) fn clk_peri_freq() -> u32 {
    125_000_000
}

pub(crate) fn clk_rtc_freq() -> u32 {
    46875
}

unsafe fn start_xosc() {
    const XOSC_MHZ: u32 = 12;
    pac::XOSC
        .ctrl()
        .write(|w| w.set_freq_range(pac::xosc::vals::CtrlFreqRange::_1_15MHZ));

    let startup_delay = (((XOSC_MHZ * 1_000_000) / 1000) + 128) / 256;
    pac::XOSC.startup().write(|w| w.set_delay(startup_delay as u16));
    pac::XOSC.ctrl().write(|w| {
        w.set_freq_range(pac::xosc::vals::CtrlFreqRange::_1_15MHZ);
        w.set_enable(pac::xosc::vals::Enable::ENABLE);
    });
    while !pac::XOSC.status().read().stable() {}
}

unsafe fn configure_pll(p: pac::pll::Pll, refdiv: u32, vco_freq: u32, post_div1: u8, post_div2: u8) {
    let ref_freq = XOSC_MHZ * 1_000_000 / refdiv;

    let fbdiv = vco_freq / ref_freq;
    assert!(fbdiv >= 16 && fbdiv <= 320);
    assert!(post_div1 >= 1 && post_div1 <= 7);
    assert!(post_div2 >= 1 && post_div2 <= 7);
    assert!(post_div2 <= post_div1);
    assert!(ref_freq <= (vco_freq / 16));

    // do not disrupt PLL that is already correctly configured and operating
    let cs = p.cs().read();
    let prim = p.prim().read();
    if cs.lock()
        && cs.refdiv() == refdiv as _
        && p.fbdiv_int().read().fbdiv_int() == fbdiv as _
        && prim.postdiv1() == post_div1
        && prim.postdiv2() == post_div2
    {
        return;
    }

    // Reset it
    let mut peris = reset::Peripherals(0);
    match p {
        pac::PLL_SYS => peris.set_pll_sys(true),
        pac::PLL_USB => peris.set_pll_usb(true),
        _ => unreachable!(),
    }
    reset::reset(peris);
    reset::unreset_wait(peris);

    // Load VCO-related dividers before starting VCO
    p.cs().write(|w| w.set_refdiv(refdiv as _));
    p.fbdiv_int().write(|w| w.set_fbdiv_int(fbdiv as _));

    // Turn on PLL
    p.pwr().modify(|w| {
        w.set_pd(false);
        w.set_vcopd(false);
        w.set_postdivpd(true);
    });

    // Wait for PLL to lock
    while !p.cs().read().lock() {}

    // Wait for PLL to lock
    p.prim().write(|w| {
        w.set_postdiv1(post_div1);
        w.set_postdiv2(post_div2);
    });

    // Turn on post divider
    p.pwr().modify(|w| w.set_postdivpd(false));
}

/// Random number generator based on the ROSC RANDOMBIT register.
///
/// This will not produce random values if the ROSC is stopped or run at some
/// harmonic of the bus frequency. With default clock settings these are not
/// issues.
pub struct RoscRng;

impl RoscRng {
    fn next_u8() -> u8 {
        let random_reg = pac::ROSC.randombit();
        let mut acc = 0;
        for _ in 0..u8::BITS {
            acc <<= 1;
            acc |= unsafe { random_reg.read().randombit() as u8 };
        }
        acc
    }
}

impl rand_core::RngCore for RoscRng {
    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), rand_core::Error> {
        Ok(self.fill_bytes(dest))
    }

    fn next_u32(&mut self) -> u32 {
        rand_core::impls::next_u32_via_fill(self)
    }

    fn next_u64(&mut self) -> u64 {
        rand_core::impls::next_u64_via_fill(self)
    }

    fn fill_bytes(&mut self, dest: &mut [u8]) {
        dest.fill_with(Self::next_u8)
    }
}