arty_a7: add divided clocks as available input peripherals so you're not stuck with 100MHz

crates/fayalite/src/vendor/xilinx/arty_a7.rs

@@ -3,7 +3,7 @@
 
 use crate::{
     intern::{Intern, Interned},
-    module::{instance_with_loc, wire_with_loc},
+    module::{instance_with_loc, reg_builder_with_loc, wire_with_loc},
     platform::{
         DynPlatform, Peripheral, PeripheralRef, Peripherals, PeripheralsBuilderFactory,
         PeripheralsBuilderFinished, Platform, PlatformAspectSet,
@@ -12,7 +12,7 @@ use crate::{
     prelude::*,
     vendor::xilinx::{
         Device, XdcCreateClockAnnotation, XdcIOStandardAnnotation, XdcLocationAnnotation,
-        primitives::{self, BUFGCE, STARTUPE2_default_inputs},
+        primitives,
     },
 };
 use ordered_float::NotNan;
@@ -66,7 +66,7 @@ arty_a7_platform! {
 
 #[derive(Debug)]
 pub struct ArtyA7Peripherals {
-    clk100: Peripheral<ClockInput>,
+    clk100_div_pow2: [Peripheral<ClockInput>; 4],
     rst: Peripheral<Reset>,
     rst_sync: Peripheral<SyncReset>,
     ld0: Peripheral<RgbLed>,
@@ -83,7 +83,7 @@ pub struct ArtyA7Peripherals {
 impl Peripherals for ArtyA7Peripherals {
     fn append_peripherals<'a>(&'a self, peripherals: &mut Vec<PeripheralRef<'a, CanonicalType>>) {
         let Self {
-            clk100,
+            clk100_div_pow2,
             rst,
             rst_sync,
             ld0,
@@ -95,7 +95,7 @@ impl Peripherals for ArtyA7Peripherals {
             ld6,
             ld7,
         } = self;
-        clk100.append_peripherals(peripherals);
+        clk100_div_pow2.append_peripherals(peripherals);
         rst.append_peripherals(peripherals);
         rst_sync.append_peripherals(peripherals);
         ld0.append_peripherals(peripherals);
@@ -168,9 +168,20 @@ impl Platform for ArtyA7Platform {
         builder_factory: PeripheralsBuilderFactory<'builder>,
     ) -> (Self::Peripherals, PeripheralsBuilderFinished<'builder>) {
         let mut builder = builder_factory.builder();
+
+        let clk100_div_pow2 = std::array::from_fn(|log2_divisor| {
+            let divisor = 1u64 << log2_divisor;
+            let name = if divisor != 1 {
+                format!("clk100_div_{divisor}")
+            } else {
+                "clk100".into()
+            };
+            builder.input_peripheral(name, ClockInput::new(100e6 / divisor as f64))
+        });
+        builder.add_conflicts(Vec::from_iter(clk100_div_pow2.iter().map(|v| v.id())));
         (
             ArtyA7Peripherals {
-                clk100: builder.input_peripheral("clk100", ClockInput::new(100e6)),
+                clk100_div_pow2,
                 rst: builder.input_peripheral("rst", Reset),
                 rst_sync: builder.input_peripheral("rst_sync", SyncReset),
                 ld0: builder.output_peripheral("ld0", RgbLed),
@@ -192,7 +203,7 @@ impl Platform for ArtyA7Platform {
 
     fn add_peripherals_in_wrapper_module(&self, m: &ModuleBuilder, peripherals: Self::Peripherals) {
         let ArtyA7Peripherals {
-            clk100,
+            clk100_div_pow2,
             rst,
             rst_sync,
             ld0,
@@ -249,30 +260,82 @@ impl Platform for ArtyA7Platform {
             connect(buf.T, false);
             buf.I
         };
-        let clock_annotation = XdcCreateClockAnnotation {
+        let mut frequency = clk100_div_pow2[0].ty().frequency();
-            period: NotNan::new(1e9 / clk100.ty().frequency()).expect("known to be valid"),
+        let mut log2_divisor = 0;
+        let mut clk = None;
+        for (cur_log2_divisor, p) in clk100_div_pow2.into_iter().enumerate() {
+            let Some(p) = p.into_used() else {
+                continue;
             };
+            debug_assert!(
+                clk.is_none(),
+                "conflict-handling logic should ensure at most one clock is used",
+            );
+            frequency = p.ty().frequency();
+            clk = Some(p);
+            log2_divisor = cur_log2_divisor;
+        }
         let clk100_buf = make_buffered_input("clk100", "E3", "LVCMOS33", false);
         let startup = instance_with_loc(
             "startup",
-            STARTUPE2_default_inputs(),
+            primitives::STARTUPE2_default_inputs(),
             SourceLocation::builtin(),
         );
-        let clk100_sync = instance_with_loc("clk100_sync", BUFGCE(), SourceLocation::builtin());
+        let clk_global_buf = instance_with_loc(
-        connect(clk100_sync.CE, startup.EOS);
+            "clk_global_buf",
-        connect(clk100_sync.I, clk100_buf);
+            primitives::BUFGCE(),
-        let clk100_out = wire_with_loc("clk100_out", SourceLocation::builtin(), Clock);
+            SourceLocation::builtin(),
-        connect(clk100_out, clk100_sync.O);
+        );
-        annotate(clk100_out, clock_annotation);
+        connect(clk_global_buf.CE, startup.EOS);
-        annotate(clk100_out, DontTouchAnnotation);
+        let mut clk_global_buf_in = clk100_buf.to_clock();
-        if let Some(clk100) = clk100.into_used() {
+        for prev_log2_divisor in 0..log2_divisor {
-            connect(clk100.instance_io_field().clk, clk100_out);
+            let prev_divisor = 1u64 << prev_log2_divisor;
+            let clk_in = wire_with_loc(
+                &format!("clk_div_{prev_divisor}"),
+                SourceLocation::builtin(),
+                Clock,
+            );
+            connect(clk_in, clk_global_buf_in);
+            annotate(
+                clk_in,
+                XdcCreateClockAnnotation {
+                    period: NotNan::new(1e9 / (100e6 / prev_divisor as f64))
+                        .expect("known to be valid"),
+                },
+            );
+            annotate(clk_in, DontTouchAnnotation);
+            let cd = wire_with_loc(
+                &format!("clk_div_{prev_divisor}_in"),
+                SourceLocation::builtin(),
+                ClockDomain[AsyncReset],
+            );
+            connect(cd.clk, clk_in);
+            connect(cd.rst, (!startup.EOS).to_async_reset());
+            let divider = reg_builder_with_loc("divider", SourceLocation::builtin())
+                .clock_domain(cd)
+                .reset(false)
+                .build();
+            connect(divider, !divider);
+            clk_global_buf_in = divider.to_clock();
+        }
+        connect(clk_global_buf.I, clk_global_buf_in);
+        let clk_out = wire_with_loc("clk_out", SourceLocation::builtin(), Clock);
+        connect(clk_out, clk_global_buf.O);
+        annotate(
+            clk_out,
+            XdcCreateClockAnnotation {
+                period: NotNan::new(1e9 / frequency).expect("known to be valid"),
+            },
+        );
+        annotate(clk_out, DontTouchAnnotation);
+        if let Some(clk) = clk {
+            connect(clk.instance_io_field().clk, clk_out);
         }
         let rst_value = {
             let rst_buf = make_buffered_input("rst", "C2", "LVCMOS33", true);
             let rst_sync = instance_with_loc("rst_sync", reset_sync(), SourceLocation::builtin());
-            connect(rst_sync.clk, clk100_sync.O);
+            connect(rst_sync.clk, clk_out);
-            connect(rst_sync.inp, rst_buf);
+            connect(rst_sync.inp, rst_buf | !startup.EOS);
             rst_sync.out
         };
         if let Some(rst) = rst.into_used() {

crates/fayalite/src/vendor/xilinx/primitives.rs

@@ -33,7 +33,7 @@ pub fn BUFGCE() {
     #[hdl]
     let CE: Bool = m.input();
     #[hdl]
-    let I: Bool = m.input();
+    let I: Clock = m.input();
 }
 
 #[hdl_module(extern)]