stm32/rcc: refactor f7.

embassy-stm32/src/rcc/f7.rs

@@ -1,5 +1,7 @@
-use crate::pac::pwr::vals::Vos;
+pub use crate::pac::rcc::vals::{
-use crate::pac::rcc::vals::{Hpre, Pllm, Plln, Pllp, Pllq, Pllsrc, Ppre, Sw};
+    Hpre as AHBPrescaler, Pllm as PllPreDiv, Plln as PllMul, Pllp, Pllq, Pllr, Pllsrc as PllSource,
+    Ppre as APBPrescaler, Sw as Sysclk,
+};
 use crate::pac::{FLASH, PWR, RCC};
 use crate::rcc::{set_freqs, Clocks};
 use crate::time::Hertz;
@@ -7,299 +9,304 @@ use crate::time::Hertz;
 /// HSI speed
 pub const HSI_FREQ: Hertz = Hertz(16_000_000);
 
-/// Clocks configuration
+#[derive(Clone, Copy, Eq, PartialEq)]
-#[non_exhaustive]
+pub enum HseMode {
-#[derive(Default)]
+    /// crystal/ceramic oscillator (HSEBYP=0)
-pub struct Config {
+    Oscillator,
-    pub hse: Option<Hertz>,
+    /// external analog clock (low swing) (HSEBYP=1)
-    pub bypass_hse: bool,
+    Bypass,
-    pub hclk: Option<Hertz>,
+}
-    pub sys_ck: Option<Hertz>,
+
-    pub pclk1: Option<Hertz>,
+#[derive(Clone, Copy, Eq, PartialEq)]
-    pub pclk2: Option<Hertz>,
+pub struct Hse {
+    /// HSE frequency.
+    pub freq: Hertz,
+    /// HSE mode.
+    pub mode: HseMode,
+}
+
+#[derive(Clone, Copy)]
+pub struct Pll {
+    /// PLL pre-divider (DIVM).
+    pub prediv: PllPreDiv,
+
+    /// PLL multiplication factor.
+    pub mul: PllMul,
+
+    /// PLL P division factor. If None, PLL P output is disabled.
+    pub divp: Option<Pllp>,
+    /// PLL Q division factor. If None, PLL Q output is disabled.
+    pub divq: Option<Pllq>,
+    /// PLL R division factor. If None, PLL R output is disabled.
+    pub divr: Option<Pllr>,
+}
+
+/// Configuration of the core clocks
+#[non_exhaustive]
+pub struct Config {
+    pub hsi: bool,
+    pub hse: Option<Hse>,
+    pub sys: Sysclk,
+
+    pub pll_src: PllSource,
+
+    pub pll: Option<Pll>,
+    pub plli2s: Option<Pll>,
+    pub pllsai: Option<Pll>,
+
+    pub ahb_pre: AHBPrescaler,
+    pub apb1_pre: APBPrescaler,
+    pub apb2_pre: APBPrescaler,
 
-    pub pll48: bool,
     pub ls: super::LsConfig,
 }
 
-fn setup_pll(pllsrcclk: u32, use_hse: bool, pllsysclk: Option<u32>, pll48clk: bool) -> PllResults {
+impl Default for Config {
-    let sysclk = pllsysclk.unwrap_or(pllsrcclk);
+    fn default() -> Self {
-    if pllsysclk.is_none() && !pll48clk {
+        Self {
-        RCC.pllcfgr().modify(|w| w.set_pllsrc(Pllsrc::from_bits(use_hse as u8)));
+            hsi: true,
+            hse: None,
+            sys: Sysclk::HSI,
+            pll_src: PllSource::HSI,
+            pll: None,
+            plli2s: None,
+            pllsai: None,
 
-        return PllResults {
+            ahb_pre: AHBPrescaler::DIV1,
-            use_pll: false,
+            apb1_pre: APBPrescaler::DIV1,
-            pllsysclk: None,
+            apb2_pre: APBPrescaler::DIV1,
-            pll48clk: None,
-        };
-    }
-    // Input divisor from PLL source clock, must result to frequency in
-    // the range from 1 to 2 MHz
-    let pllm_min = (pllsrcclk + 1_999_999) / 2_000_000;
-    let pllm_max = pllsrcclk / 1_000_000;
 
-    // Sysclk output divisor must be one of 2, 4, 6 or 8
+            ls: Default::default(),
-    let sysclk_div = core::cmp::min(8, (432_000_000 / sysclk) & !1);
+        }
-
-    let target_freq = if pll48clk { 48_000_000 } else { sysclk * sysclk_div };
-
-    // Find the lowest pllm value that minimize the difference between
-    // target frequency and the real vco_out frequency.
-    let pllm = unwrap!((pllm_min..=pllm_max).min_by_key(|pllm| {
-        let vco_in = pllsrcclk / pllm;
-        let plln = target_freq / vco_in;
-        target_freq - vco_in * plln
-    }));
-
-    let vco_in = pllsrcclk / pllm;
-    assert!((1_000_000..=2_000_000).contains(&vco_in));
-
-    // Main scaler, must result in >= 100MHz (>= 192MHz for F401)
-    // and <= 432MHz, min 50, max 432
-    let plln = if pll48clk {
-        // try the different valid pllq according to the valid
-        // main scaller values, and take the best
-        let pllq = unwrap!((4..=9).min_by_key(|pllq| {
-            let plln = 48_000_000 * pllq / vco_in;
-            let pll48_diff = 48_000_000 - vco_in * plln / pllq;
-            let sysclk_diff = (sysclk as i32 - (vco_in * plln / sysclk_div) as i32).abs();
-            (pll48_diff, sysclk_diff)
-        }));
-        48_000_000 * pllq / vco_in
-    } else {
-        sysclk * sysclk_div / vco_in
-    };
-
-    let pllp = (sysclk_div / 2) - 1;
-
-    let pllq = (vco_in * plln + 47_999_999) / 48_000_000;
-    let real_pll48clk = vco_in * plln / pllq;
-
-    RCC.pllcfgr().modify(|w| {
-        w.set_pllm(Pllm::from_bits(pllm as u8));
-        w.set_plln(Plln::from_bits(plln as u16));
-        w.set_pllp(Pllp::from_bits(pllp as u8));
-        w.set_pllq(Pllq::from_bits(pllq as u8));
-        w.set_pllsrc(Pllsrc::from_bits(use_hse as u8));
-    });
-
-    let real_pllsysclk = vco_in * plln / sysclk_div;
-
-    PllResults {
-        use_pll: true,
-        pllsysclk: Some(real_pllsysclk),
-        pll48clk: if pll48clk { Some(real_pll48clk) } else { None },
     }
 }
 
-fn flash_setup(sysclk: u32) {
+pub(crate) unsafe fn init(config: Config) {
+    // always enable overdrive for now. Make it configurable in the future.
+    PWR.cr1().modify(|w| w.set_oden(true));
+    while !PWR.csr1().read().odrdy() {}
+
+    PWR.cr1().modify(|w| w.set_odswen(true));
+    while !PWR.csr1().read().odswrdy() {}
+
+    // Configure HSI
+    let hsi = match config.hsi {
+        false => {
+            RCC.cr().modify(|w| w.set_hsion(false));
+            None
+        }
+        true => {
+            RCC.cr().modify(|w| w.set_hsion(true));
+            while !RCC.cr().read().hsirdy() {}
+            Some(HSI_FREQ)
+        }
+    };
+
+    // Configure HSE
+    let hse = match config.hse {
+        None => {
+            RCC.cr().modify(|w| w.set_hseon(false));
+            None
+        }
+        Some(hse) => {
+            match hse.mode {
+                HseMode::Bypass => assert!(max::HSE_BYP.contains(&hse.freq)),
+                HseMode::Oscillator => assert!(max::HSE_OSC.contains(&hse.freq)),
+            }
+
+            RCC.cr().modify(|w| w.set_hsebyp(hse.mode != HseMode::Oscillator));
+            RCC.cr().modify(|w| w.set_hseon(true));
+            while !RCC.cr().read().hserdy() {}
+            Some(hse.freq)
+        }
+    };
+
+    // Configure PLLs.
+    let pll_input = PllInput {
+        hse,
+        hsi,
+        source: config.pll_src,
+    };
+    let pll = init_pll(PllInstance::Pll, config.pll, &pll_input);
+    let _plli2s = init_pll(PllInstance::Plli2s, config.plli2s, &pll_input);
+    let _pllsai = init_pll(PllInstance::Pllsai, config.pllsai, &pll_input);
+
+    // Configure sysclk
+    let sys = match config.sys {
+        Sysclk::HSI => unwrap!(hsi),
+        Sysclk::HSE => unwrap!(hse),
+        Sysclk::PLL1_P => unwrap!(pll.p),
+        _ => unreachable!(),
+    };
+
+    let hclk = sys / config.ahb_pre;
+    let (pclk1, pclk1_tim) = calc_pclk(hclk, config.apb1_pre);
+    let (pclk2, pclk2_tim) = calc_pclk(hclk, config.apb2_pre);
+
+    assert!(max::SYSCLK.contains(&sys));
+    assert!(max::HCLK.contains(&hclk));
+    assert!(max::PCLK1.contains(&pclk1));
+    assert!(max::PCLK2.contains(&pclk2));
+
+    let rtc = config.ls.init();
+
+    flash_setup(hclk);
+
+    RCC.cfgr().modify(|w| {
+        w.set_sw(config.sys);
+        w.set_hpre(config.ahb_pre);
+        w.set_ppre1(config.apb1_pre);
+        w.set_ppre2(config.apb2_pre);
+    });
+    while RCC.cfgr().read().sws() != config.sys {}
+
+    set_freqs(Clocks {
+        sys,
+        hclk1: hclk,
+        hclk2: hclk,
+        hclk3: hclk,
+        pclk1,
+        pclk2,
+        pclk1_tim,
+        pclk2_tim,
+        rtc,
+        pll1_q: pll.q,
+    });
+}
+
+struct PllInput {
+    source: PllSource,
+    hsi: Option<Hertz>,
+    hse: Option<Hertz>,
+}
+
+#[derive(Default)]
+#[allow(unused)]
+struct PllOutput {
+    p: Option<Hertz>,
+    q: Option<Hertz>,
+    r: Option<Hertz>,
+}
+
+#[derive(PartialEq, Eq, Clone, Copy)]
+enum PllInstance {
+    Pll,
+    Plli2s,
+    Pllsai,
+}
+
+fn pll_enable(instance: PllInstance, enabled: bool) {
+    match instance {
+        PllInstance::Pll => {
+            RCC.cr().modify(|w| w.set_pllon(enabled));
+            while RCC.cr().read().pllrdy() != enabled {}
+        }
+        PllInstance::Plli2s => {
+            RCC.cr().modify(|w| w.set_plli2son(enabled));
+            while RCC.cr().read().plli2srdy() != enabled {}
+        }
+        PllInstance::Pllsai => {
+            RCC.cr().modify(|w| w.set_pllsaion(enabled));
+            while RCC.cr().read().pllsairdy() != enabled {}
+        }
+    }
+}
+
+fn init_pll(instance: PllInstance, config: Option<Pll>, input: &PllInput) -> PllOutput {
+    // Disable PLL
+    pll_enable(instance, false);
+
+    let Some(pll) = config else { return PllOutput::default() };
+
+    let pll_src = match input.source {
+        PllSource::HSE => input.hse,
+        PllSource::HSI => input.hsi,
+    };
+
+    let pll_src = pll_src.unwrap();
+
+    let in_freq = pll_src / pll.prediv;
+    assert!(max::PLL_IN.contains(&in_freq));
+    let vco_freq = in_freq * pll.mul;
+    assert!(max::PLL_VCO.contains(&vco_freq));
+
+    let p = pll.divp.map(|div| vco_freq / div);
+    let q = pll.divq.map(|div| vco_freq / div);
+    let r = pll.divr.map(|div| vco_freq / div);
+
+    macro_rules! write_fields {
+        ($w:ident) => {
+            $w.set_plln(pll.mul);
+            if let Some(divp) = pll.divp {
+                $w.set_pllp(divp);
+            }
+            if let Some(divq) = pll.divq {
+                $w.set_pllq(divq);
+            }
+            if let Some(divr) = pll.divr {
+                $w.set_pllr(divr);
+            }
+        };
+    }
+
+    match instance {
+        PllInstance::Pll => RCC.pllcfgr().write(|w| {
+            w.set_pllm(pll.prediv);
+            w.set_pllsrc(input.source);
+            write_fields!(w);
+        }),
+        PllInstance::Plli2s => RCC.plli2scfgr().write(|w| {
+            write_fields!(w);
+        }),
+        PllInstance::Pllsai => RCC.pllsaicfgr().write(|w| {
+            write_fields!(w);
+        }),
+    }
+
+    // Enable PLL
+    pll_enable(instance, true);
+
+    PllOutput { p, q, r }
+}
+
+fn flash_setup(clk: Hertz) {
     use crate::pac::flash::vals::Latency;
 
     // Be conservative with voltage ranges
     const FLASH_LATENCY_STEP: u32 = 30_000_000;
 
-    critical_section::with(|_| {
+    let latency = (clk.0 - 1) / FLASH_LATENCY_STEP;
-        FLASH
+    debug!("flash: latency={}", latency);
-            .acr()
+
-            .modify(|w| w.set_latency(Latency::from_bits(((sysclk - 1) / FLASH_LATENCY_STEP) as u8)));
+    let latency = Latency::from_bits(latency as u8);
+    FLASH.acr().write(|w| {
+        w.set_latency(latency);
     });
+    while FLASH.acr().read().latency() != latency {}
 }
 
-pub(crate) unsafe fn init(config: Config) {
+fn calc_pclk<D>(hclk: Hertz, ppre: D) -> (Hertz, Hertz)
-    if let Some(hse) = config.hse {
+where
-        if config.bypass_hse {
+    Hertz: core::ops::Div<D, Output = Hertz>,
-            assert!((max::HSE_BYPASS_MIN..=max::HSE_BYPASS_MAX).contains(&hse.0));
+{
-        } else {
+    let pclk = hclk / ppre;
-            assert!((max::HSE_OSC_MIN..=max::HSE_OSC_MAX).contains(&hse.0));
+    let pclk_tim = if hclk == pclk { pclk } else { pclk * 2u32 };
-        }
+    (pclk, pclk_tim)
-    }
-
-    let pllsrcclk = config.hse.map(|hse| hse.0).unwrap_or(HSI_FREQ.0);
-    let sysclk = config.sys_ck.map(|sys| sys.0).unwrap_or(pllsrcclk);
-    let sysclk_on_pll = sysclk != pllsrcclk;
-
-    assert!((max::SYSCLK_MIN..=max::SYSCLK_MAX).contains(&sysclk));
-
-    let plls = setup_pll(
-        pllsrcclk,
-        config.hse.is_some(),
-        if sysclk_on_pll { Some(sysclk) } else { None },
-        config.pll48,
-    );
-
-    if config.pll48 {
-        let freq = unwrap!(plls.pll48clk);
-
-        assert!((max::PLL_48_CLK as i32 - freq as i32).abs() <= max::PLL_48_TOLERANCE as i32);
-    }
-
-    let sysclk = if sysclk_on_pll { unwrap!(plls.pllsysclk) } else { sysclk };
-
-    // AHB prescaler
-    let hclk = config.hclk.map(|h| h.0).unwrap_or(sysclk);
-    let (hpre_bits, hpre_div) = match (sysclk + hclk - 1) / hclk {
-        0 => unreachable!(),
-        1 => (Hpre::DIV1, 1),
-        2 => (Hpre::DIV2, 2),
-        3..=5 => (Hpre::DIV4, 4),
-        6..=11 => (Hpre::DIV8, 8),
-        12..=39 => (Hpre::DIV16, 16),
-        40..=95 => (Hpre::DIV64, 64),
-        96..=191 => (Hpre::DIV128, 128),
-        192..=383 => (Hpre::DIV256, 256),
-        _ => (Hpre::DIV512, 512),
-    };
-
-    // Calculate real AHB clock
-    let hclk = sysclk / hpre_div;
-
-    assert!(hclk <= max::HCLK_MAX);
-
-    let pclk1 = config
-        .pclk1
-        .map(|p| p.0)
-        .unwrap_or_else(|| core::cmp::min(max::PCLK1_MAX, hclk));
-
-    let (ppre1_bits, ppre1) = match (hclk + pclk1 - 1) / pclk1 {
-        0 => unreachable!(),
-        1 => (0b000, 1),
-        2 => (0b100, 2),
-        3..=5 => (0b101, 4),
-        6..=11 => (0b110, 8),
-        _ => (0b111, 16),
-    };
-    let timer_mul1 = if ppre1 == 1 { 1 } else { 2 };
-
-    // Calculate real APB1 clock
-    let pclk1 = hclk / ppre1;
-    assert!((max::PCLK1_MIN..=max::PCLK1_MAX).contains(&pclk1));
-
-    let pclk2 = config
-        .pclk2
-        .map(|p| p.0)
-        .unwrap_or_else(|| core::cmp::min(max::PCLK2_MAX, hclk));
-    let (ppre2_bits, ppre2) = match (hclk + pclk2 - 1) / pclk2 {
-        0 => unreachable!(),
-        1 => (0b000, 1),
-        2 => (0b100, 2),
-        3..=5 => (0b101, 4),
-        6..=11 => (0b110, 8),
-        _ => (0b111, 16),
-    };
-    let timer_mul2 = if ppre2 == 1 { 1 } else { 2 };
-
-    // Calculate real APB2 clock
-    let pclk2 = hclk / ppre2;
-    assert!((max::PCLK2_MIN..=max::PCLK2_MAX).contains(&pclk2));
-
-    flash_setup(sysclk);
-
-    if config.hse.is_some() {
-        RCC.cr().modify(|w| {
-            w.set_hsebyp(config.bypass_hse);
-            w.set_hseon(true);
-        });
-        while !RCC.cr().read().hserdy() {}
-    }
-
-    if plls.use_pll {
-        RCC.cr().modify(|w| w.set_pllon(false));
-
-        // setup VOSScale
-        let vos_scale = if sysclk <= 144_000_000 {
-            3
-        } else if sysclk <= 168_000_000 {
-            2
-        } else {
-            1
-        };
-        PWR.cr1().modify(|w| {
-            w.set_vos(match vos_scale {
-                3 => Vos::SCALE3,
-                2 => Vos::SCALE2,
-                1 => Vos::SCALE1,
-                _ => panic!("Invalid VOS Scale."),
-            })
-        });
-
-        RCC.cr().modify(|w| w.set_pllon(true));
-
-        if hclk > max::HCLK_OVERDRIVE_FREQUENCY {
-            PWR.cr1().modify(|w| w.set_oden(true));
-            while !PWR.csr1().read().odrdy() {}
-
-            PWR.cr1().modify(|w| w.set_odswen(true));
-            while !PWR.csr1().read().odswrdy() {}
-        }
-
-        while !RCC.cr().read().pllrdy() {}
-    }
-
-    RCC.cfgr().modify(|w| {
-        w.set_ppre2(Ppre::from_bits(ppre2_bits));
-        w.set_ppre1(Ppre::from_bits(ppre1_bits));
-        w.set_hpre(hpre_bits);
-    });
-
-    // Wait for the new prescalers to kick in
-    // "The clocks are divided with the new prescaler factor from 1 to 16 AHB cycles after write"
-    cortex_m::asm::delay(16);
-
-    RCC.cfgr().modify(|w| {
-        w.set_sw(if sysclk_on_pll {
-            Sw::PLL1_P
-        } else if config.hse.is_some() {
-            Sw::HSE
-        } else {
-            Sw::HSI
-        })
-    });
-
-    let rtc = config.ls.init();
-
-    set_freqs(Clocks {
-        sys: Hertz(sysclk),
-        pclk1: Hertz(pclk1),
-        pclk2: Hertz(pclk2),
-
-        pclk1_tim: Hertz(pclk1 * timer_mul1),
-        pclk2_tim: Hertz(pclk2 * timer_mul2),
-
-        hclk1: Hertz(hclk),
-        hclk2: Hertz(hclk),
-        hclk3: Hertz(hclk),
-
-        pll1_q: plls.pll48clk.map(Hertz),
-
-        rtc,
-    });
-}
-
-struct PllResults {
-    use_pll: bool,
-    pllsysclk: Option<u32>,
-    pll48clk: Option<u32>,
 }
 
 mod max {
-    pub(crate) const HSE_OSC_MIN: u32 = 4_000_000;
+    use core::ops::RangeInclusive;
-    pub(crate) const HSE_OSC_MAX: u32 = 26_000_000;
-    pub(crate) const HSE_BYPASS_MIN: u32 = 1_000_000;
-    pub(crate) const HSE_BYPASS_MAX: u32 = 50_000_000;
 
-    pub(crate) const HCLK_MAX: u32 = 216_000_000;
+    use crate::time::Hertz;
-    pub(crate) const HCLK_OVERDRIVE_FREQUENCY: u32 = 180_000_000;
 
-    pub(crate) const SYSCLK_MIN: u32 = 12_500_000;
+    pub(crate) const HSE_OSC: RangeInclusive<Hertz> = Hertz(4_000_000)..=Hertz(26_000_000);
-    pub(crate) const SYSCLK_MAX: u32 = 216_000_000;
+    pub(crate) const HSE_BYP: RangeInclusive<Hertz> = Hertz(1_000_000)..=Hertz(50_000_000);
 
-    pub(crate) const PCLK1_MIN: u32 = SYSCLK_MIN;
+    pub(crate) const SYSCLK: RangeInclusive<Hertz> = Hertz(12_500_000)..=Hertz(216_000_000);
-    pub(crate) const PCLK1_MAX: u32 = SYSCLK_MAX / 4;
+    pub(crate) const HCLK: RangeInclusive<Hertz> = Hertz(12_500_000)..=Hertz(216_000_000);
+    pub(crate) const PCLK1: RangeInclusive<Hertz> = Hertz(12_500_000)..=Hertz(216_000_000 / 4);
+    pub(crate) const PCLK2: RangeInclusive<Hertz> = Hertz(12_500_000)..=Hertz(216_000_000 / 2);
 
-    pub(crate) const PCLK2_MIN: u32 = SYSCLK_MIN;
+    pub(crate) const PLL_IN: RangeInclusive<Hertz> = Hertz(1_000_000)..=Hertz(2_100_000);
-    pub(crate) const PCLK2_MAX: u32 = SYSCLK_MAX / 2;
+    pub(crate) const PLL_VCO: RangeInclusive<Hertz> = Hertz(100_000_000)..=Hertz(432_000_000);
-
-    // USB specification allows +-0.25%
-    pub(crate) const PLL_48_CLK: u32 = 48_000_000;
-    pub(crate) const PLL_48_TOLERANCE: u32 = 120_000;
 }

examples/stm32f7/src/bin/eth.rs

@@ -10,7 +10,7 @@ use embassy_stm32::eth::generic_smi::GenericSMI;
 use embassy_stm32::eth::{Ethernet, PacketQueue};
 use embassy_stm32::peripherals::ETH;
 use embassy_stm32::rng::Rng;
-use embassy_stm32::time::mhz;
+use embassy_stm32::time::Hertz;
 use embassy_stm32::{bind_interrupts, eth, peripherals, rng, Config};
 use embassy_time::Timer;
 use embedded_io_async::Write;
@@ -33,7 +33,25 @@ async fn net_task(stack: &'static Stack<Device>) -> ! {
 #[embassy_executor::main]
 async fn main(spawner: Spawner) -> ! {
     let mut config = Config::default();
-    config.rcc.sys_ck = Some(mhz(200));
+    {
+        use embassy_stm32::rcc::*;
+        config.rcc.hse = Some(Hse {
+            freq: Hertz(8_000_000),
+            mode: HseMode::Bypass,
+        });
+        config.rcc.pll_src = PllSource::HSE;
+        config.rcc.pll = Some(Pll {
+            prediv: PllPreDiv::DIV4,
+            mul: PllMul::MUL216,
+            divp: Some(Pllp::DIV2), // 8mhz / 4 * 216 / 2 = 216Mhz
+            divq: None,
+            divr: None,
+        });
+        config.rcc.ahb_pre = AHBPrescaler::DIV1;
+        config.rcc.apb1_pre = APBPrescaler::DIV4;
+        config.rcc.apb2_pre = APBPrescaler::DIV2;
+        config.rcc.sys = Sysclk::PLL1_P;
+    }
     let p = embassy_stm32::init(config);
 
     info!("Hello World!");

examples/stm32f7/src/bin/hello.rs

@@ -4,15 +4,13 @@
 
 use defmt::info;
 use embassy_executor::Spawner;
-use embassy_stm32::time::Hertz;
 use embassy_stm32::Config;
 use embassy_time::Timer;
 use {defmt_rtt as _, panic_probe as _};
 
 #[embassy_executor::main]
 async fn main(_spawner: Spawner) -> ! {
-    let mut config = Config::default();
+    let config = Config::default();
-    config.rcc.sys_ck = Some(Hertz(84_000_000));
     let _p = embassy_stm32::init(config);
 
     loop {

examples/stm32f7/src/bin/sdmmc.rs

@@ -5,7 +5,7 @@
 use defmt::*;
 use embassy_executor::Spawner;
 use embassy_stm32::sdmmc::Sdmmc;
-use embassy_stm32::time::mhz;
+use embassy_stm32::time::{mhz, Hertz};
 use embassy_stm32::{bind_interrupts, peripherals, sdmmc, Config};
 use {defmt_rtt as _, panic_probe as _};
 
@@ -16,8 +16,25 @@ bind_interrupts!(struct Irqs {
 #[embassy_executor::main]
 async fn main(_spawner: Spawner) {
     let mut config = Config::default();
-    config.rcc.sys_ck = Some(mhz(200));
+    {
-    config.rcc.pll48 = true;
+        use embassy_stm32::rcc::*;
+        config.rcc.hse = Some(Hse {
+            freq: Hertz(8_000_000),
+            mode: HseMode::Bypass,
+        });
+        config.rcc.pll_src = PllSource::HSE;
+        config.rcc.pll = Some(Pll {
+            prediv: PllPreDiv::DIV4,
+            mul: PllMul::MUL216,
+            divp: Some(Pllp::DIV2), // 8mhz / 4 * 216 / 2 = 216Mhz
+            divq: Some(Pllq::DIV9), // 8mhz / 4 * 216 / 9 = 48Mhz
+            divr: None,
+        });
+        config.rcc.ahb_pre = AHBPrescaler::DIV1;
+        config.rcc.apb1_pre = APBPrescaler::DIV4;
+        config.rcc.apb2_pre = APBPrescaler::DIV2;
+        config.rcc.sys = Sysclk::PLL1_P;
+    }
     let p = embassy_stm32::init(config);
 
     info!("Hello World!");

examples/stm32f7/src/bin/usb_serial.rs

@@ -4,7 +4,7 @@
 
 use defmt::{panic, *};
 use embassy_executor::Spawner;
-use embassy_stm32::time::mhz;
+use embassy_stm32::time::Hertz;
 use embassy_stm32::usb_otg::{Driver, Instance};
 use embassy_stm32::{bind_interrupts, peripherals, usb_otg, Config};
 use embassy_usb::class::cdc_acm::{CdcAcmClass, State};
@@ -22,10 +22,25 @@ async fn main(_spawner: Spawner) {
     info!("Hello World!");
 
     let mut config = Config::default();
-    config.rcc.hse = Some(mhz(8));
+    {
-    config.rcc.pll48 = true;
+        use embassy_stm32::rcc::*;
-    config.rcc.sys_ck = Some(mhz(200));
+        config.rcc.hse = Some(Hse {
-
+            freq: Hertz(8_000_000),
+            mode: HseMode::Bypass,
+        });
+        config.rcc.pll_src = PllSource::HSE;
+        config.rcc.pll = Some(Pll {
+            prediv: PllPreDiv::DIV4,
+            mul: PllMul::MUL216,
+            divp: Some(Pllp::DIV2), // 8mhz / 4 * 216 / 2 = 216Mhz
+            divq: Some(Pllq::DIV9), // 8mhz / 4 * 216 / 9 = 48Mhz
+            divr: None,
+        });
+        config.rcc.ahb_pre = AHBPrescaler::DIV1;
+        config.rcc.apb1_pre = APBPrescaler::DIV4;
+        config.rcc.apb2_pre = APBPrescaler::DIV2;
+        config.rcc.sys = Sysclk::PLL1_P;
+    }
     let p = embassy_stm32::init(config);
 
     // Create the driver, from the HAL.

tests/stm32/src/common.rs

@@ -233,7 +233,23 @@ pub fn config() -> Config {
 
     #[cfg(feature = "stm32f767zi")]
     {
-        config.rcc.sys_ck = Some(Hertz(200_000_000));
+        use embassy_stm32::rcc::*;
+        config.rcc.hse = Some(Hse {
+            freq: Hertz(8_000_000),
+            mode: HseMode::Bypass,
+        });
+        config.rcc.pll_src = PllSource::HSE;
+        config.rcc.pll = Some(Pll {
+            prediv: PllPreDiv::DIV4,
+            mul: PllMul::MUL216,
+            divp: Some(Pllp::DIV2), // 8mhz / 4 * 216 / 2 = 216Mhz.
+            divq: None,
+            divr: None,
+        });
+        config.rcc.ahb_pre = AHBPrescaler::DIV1;
+        config.rcc.apb1_pre = APBPrescaler::DIV4;
+        config.rcc.apb2_pre = APBPrescaler::DIV2;
+        config.rcc.sys = Sysclk::PLL1_P;
     }
 
     #[cfg(feature = "stm32h563zi")]