99 lines
2.5 KiB
Zig
99 lines
2.5 KiB
Zig
// Rumpk Layer 0: UART Driver
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// Minimal serial output for QEMU 'virt' machine
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// Supports PL011 (ARM64) and 16550A (RISC-V)
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const std = @import("std");
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const builtin = @import("builtin");
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// ARM64 PL011 Constants
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const PL011_BASE: usize = 0x09000000;
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const PL011_DR: usize = 0x00;
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const PL011_FR: usize = 0x18;
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const PL011_TXFF: u32 = 1 << 5;
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// RISC-V 16550A Constants
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const NS16550A_BASE: usize = 0x10000000;
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const NS16550A_THR: usize = 0x00; // Transmitter Holding Register
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const NS16550A_LSR: usize = 0x05; // Line Status Register
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const NS16550A_THRE: u8 = 1 << 5; // Transmitter Holding Register Empty
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pub fn init() void {
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// QEMU devices are usually pre-initialized by firmware (EDK2/OpenSBI)
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}
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pub fn init_riscv() void {
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// Explicit init if needed, currently empty as we rely on pre-init
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}
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fn write_char_arm64(c: u8) void {
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const dr: *volatile u32 = @ptrFromInt(PL011_BASE + PL011_DR);
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const fr: *volatile u32 = @ptrFromInt(PL011_BASE + PL011_FR);
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while ((fr.* & PL011_TXFF) != 0) {}
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dr.* = c;
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}
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fn write_char_riscv64(c: u8) void {
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const thr: *volatile u8 = @ptrFromInt(NS16550A_BASE + NS16550A_THR);
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const lsr: *volatile u8 = @ptrFromInt(NS16550A_BASE + NS16550A_LSR);
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// Wait for THRE (Transmitter Holding Register Empty)
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while ((lsr.* & NS16550A_THRE) == 0) {}
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thr.* = c;
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}
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fn write_char(c: u8) void {
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switch (builtin.cpu.arch) {
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.aarch64 => write_char_arm64(c),
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.riscv64 => write_char_riscv64(c),
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else => {}, // Do nothing on others
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}
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}
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pub fn write_bytes(bytes: []const u8) void {
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for (bytes) |b| {
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if (b == '\n') {
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write_char('\r');
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}
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write_char(b);
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}
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}
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pub fn puts(s: []const u8) void {
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write_bytes(s);
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}
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pub fn putc(c: u8) void {
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if (c == '\n') {
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write_char('\r');
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}
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write_char(c);
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}
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pub fn print(s: []const u8) void {
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puts(s);
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}
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pub const Writer = struct {
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pub const Error = error{};
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pub fn write(self: Writer, bytes: []const u8) Error!usize {
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_ = self;
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write_bytes(bytes);
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return bytes.len;
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}
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pub fn print(self: Writer, comptime fmt: []const u8, args: anytype) Error!void {
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return std.fmt.format(self, fmt, args);
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}
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};
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pub fn print_hex(value: usize) void {
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const hex_chars = "0123456789ABCDEF";
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write_bytes("0x");
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var i: usize = 0;
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while (i < 16) : (i += 1) {
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const shift: u6 = @intCast((15 - i) * 4);
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const nibble = (value >> shift) & 0xF;
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write_char(hex_chars[nibble]);
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}
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}
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