1 files changed, 0 insertions, 153 deletions
diff --git a/src/pardes/uart.zig b/src/pardes/uart.zig
deleted file mode 100644
index 7696742..0000000
--- a/src/pardes/uart.zig
+++ /dev/null
@@ -1,153 +0,0 @@
-//! UART0 as the editor's terminal: bytes out, bytes in, and nothing else.
-//!
-//! This is the whole of the firmware's I/O. There is no framebuffer and no keyboard; the board
-//! emits ANSI and consumes ANSI, and the terminal emulator on the far end of the CH340 does the
-//! rest of the work - including answering the editor's own capability queries, which travel down
-//! this wire like any other bytes.
-//!
-//! Deliberately not a `std.Io.Writer`. The ANSI encoding lives on the other side of the C ABI, next
-//! to the vaxis that produces it (see `src/pardes/app.zig` for why the seam is there and not
-//! elsewhere), so what crosses into this file is already a finished run of bytes. A writer here
-//! would be a second buffer in front of one that already exists.
-//!
-//! Two decisions worth stating, because both are measurements rather than preferences.
-//!
-//! **Batched FIFO access.** The naive push is `while (txFree() == 0) {}` then `pushByte`, once per
-//! byte: one MMIO read per byte at best, many while the FIFO is full. Reading `txFree` once and
-//! then pushing that many cuts the status reads by up to the FIFO depth (128, `hal/uart.zig:52`).
-//! At 115200 the wire costs ~86 us per byte and dwarfs either version, so today this is merely
-//! free - and it stops being free the moment the divider is raised.
-//!
-//! **UART0's configuration is never touched.** Not the divider, not the format, not the pad
-//! routing, and above all not `reset()`. The second-stage bootloader configured this block, and
-//! `hal/uart.zig:195-211` records what happens if it is reset: UART_CLKDIV returns to its power-on
-//! value, the console turns to garbage mid-sentence, and the board takes a watchdog reset with
-//! nothing readable left to explain it. Everything here touches FIFO offset 0x000 and the status
-//! register, and nothing else.
-
-const hal = @import("hal");
-const input_rescue = @import("input_rescue.zig");
-
-/// UART0: the instance the CH340 is wired to, and the one the ROM and bootloader configured.
-const uart0 = hal.uart.Uart.init(0);
-
-/// Keystrokes taken off the receiver while the transmitter was full. See `input_rescue`: without
-/// this, anything typed into a frame longer than the 128-byte FIFO was silently gone.
-var rescued: input_rescue.Ring = .{};
-
-/// Push `bytes` into the TX FIFO, blocking while it is full.
-///
-/// The spin is normally bounded by the wire - a full 128-byte FIFO drains in 11 ms at 115200 - and
-/// dropping instead of waiting would truncate an escape sequence, leaving the host terminal in the
-/// wrong colour for the rest of the session. So the wait is real backpressure.
-///
-/// But it is BOUNDED, for the reason `hal/uart.zig:182-186` gives about `update()`: a UART whose
-/// core clock has been gated never makes progress, and "on a board with no debugger an infinite
-/// spin is indistinguishable from a crash". That is not hypothetical here - it is how this port
-/// spent an afternoon: output stopped mid-boot with no panic and no watchdog (the RTC watchdog
-/// having been correctly disabled), which looked like a hang in whatever code came next rather than
-/// a stalled transmitter. A bounded wait turns that into visibly dropped output plus a counter,
-/// which is a diagnosis instead of a mystery.
-///
-/// The limit is per burst, not per call, and generous: 1,000,000 status reads is far longer than
-/// any legitimate drain and still a fraction of a second.
-pub fn write(bytes: []const u8) void {
-    dropped +%= input_rescue.pump(uart0, &rescued, bytes, 1_000_000);
-}
-
-/// Bytes abandoned because the transmitter stopped making progress. Nonzero means the console is
-/// lying about what happened, so it is worth printing.
-pub var dropped: u32 = 0;
-
-/// One byte, for callers that must not touch `.rodata` to say anything - which during bring-up is
-/// the difference between a diagnostic and a second copy of the bug being diagnosed.
-pub fn writeByte(b: u8) void {
-    var spins: u32 = 0;
-    while (uart0.txFree() == 0) {
-        spins += 1;
-        if (spins > 1_000_000) {
-            dropped +%= 1;
-            return;
-        }
-    }
-    uart0.pushByte(b);
-}
-
-/// Emit `n` bytes read from `addr` as two hex digits each, computing the digits arithmetically so
-/// nothing here reads a lookup table. Used to answer "does a load from this address return what the
-/// linker put there", which is not a question a string literal can be trusted to ask.
-pub fn dumpHex(addr: u32, n: u32) void {
-    const p: [*]const volatile u8 = @ptrFromInt(addr);
-    var i: u32 = 0;
-    while (i < n) : (i += 1) {
-        const byte = p[i];
-        for ([2]u8{ byte >> 4, byte & 0xf }) |nib| {
-            writeByte(if (nib < 10) '0' + nib else 'a' + (nib - 10));
-        }
-    }
-    writeByte('\r');
-    writeByte('\n');
-}
-
-/// A u32 as eight hex digits, reading no memory at all.
-pub fn dumpWord(v: u32) void {
-    var shift: u5 = 28;
-    while (true) {
-        const nib: u8 = @intCast((v >> shift) & 0xf);
-        writeByte(if (nib < 10) '0' + nib else 'a' + (nib - 10));
-        if (shift == 0) break;
-        shift -= 4;
-    }
-    writeByte('\r');
-    writeByte('\n');
-}
-
-/// Move whatever the host has sent into `buf`, without waiting. Returns the count.
-///
-/// Non-blocking on purpose: the loop has a frame to render and a core to pump, and the editor must
-/// not stall on a keystroke that may never come. `rxCount` is read once per call and the FIFO
-/// drained to that mark, so a fast typist or a pasted buffer cannot hold the loop here.
-pub fn read(buf: []u8) usize {
-    // RESCUED BYTES FIRST. They arrived before anything still sitting in the FIFO, and an editor
-    // that reorders keystrokes is worse than one that drops them.
-    var n = rescued.pop(buf);
-    const waiting = @min(uart0.rxCount(), buf.len - n);
-    for (buf[n..][0..waiting]) |*slot| slot.* = uart0.popByte();
-    n += waiting;
-    return n;
-}
-
-/// Take whatever has arrived off the receiver right now, without waiting and without handing it to
-/// anyone. For callers that are about to spend a while not reading: `write` does this while the
-/// transmitter is full, and the loop does it between chunks of input, because applying a keystroke
-/// gets more expensive as the line grows and 128 bytes of FIFO is only 11 ms at 115200.
-pub fn rescueNow() void {
-    input_rescue.rescue(uart0, &rescued);
-}
-
-/// Input abandoned because even the rescue buffer overflowed. Distinct from `dropped`, which is
-/// OUTPUT abandoned by a stalled transmitter.
-pub fn inputDropped() u32 {
-    return rescued.dropped;
-}
-
-/// Discard anything already received, returning how much. Used once at startup: the host-side
-/// bridge injects a window-size report before this program exists, and the bootloader's chatter has
-/// already been echoed at the host. Neither is user input.
-///
-/// Pops rather than calling `resetRxFifo`, which is a CONF0_SYNC read-modify-write plus two commits
-/// on the console UART - see this file's header.
-pub fn drainInput() u32 {
-    var discarded: u32 = 0;
-    while (uart0.rxCount() > 0) : (discarded += 1) _ = uart0.popByte();
-    discarded += @intCast(rescued.len);
-    rescued.clear();
-    return discarded;
-}
-
-/// The rate the hardware is actually producing, by reading its dividers back. Reported rather than
-/// assumed: the host has to be opened at the same rate, and a mismatch shows up as garbage on the
-/// screen rather than as an error anyone can act on.
-pub fn baudrate() u32 {
-    return uart0.baudrate(uart0.clockSource().nominalHz());
-}