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// SPDX-FileCopyrightText: 2024 Himbeer <himbeer@disroot.org>
//
// SPDX-License-Identifier: AGPL-3.0-or-later
const std = @import("std");
const fdt = @import("fdt.zig");
const paging = @import("paging.zig");
pub var default: ?Port = null;
pub const Error = error{
NoSocNode,
};
pub const Port = struct {
reg: []volatile u8,
reg_shift: u6,
const lsr_thre = 1 << 5;
pub const Writer = std.io.Writer(Port, error{}, write);
fn isWriteReady(self: Port) bool {
return self.reg[@as(usize, 5) << self.reg_shift] & lsr_thre != 0;
}
pub fn write(self: Port, bytes: []const u8) !usize {
for (bytes) |byte| {
while (!self.isWriteReady()) {}
self.reg[0] = byte;
}
return bytes.len;
}
pub fn writer(port: Port) Writer {
return .{ .context = port };
}
};
pub fn init(kmem: *paging.Table, dt: *const fdt.Tree, allocator: std.mem.Allocator) !void {
var soc = fdt.findPathExact(dt, "/soc") orelse return Error.NoSocNode;
const compatible = fdt.findCompatible(&soc, &[_][]const u8{ "ns16550", "snps,dw-apb-uart" }, 1);
const node = if (compatible.len > 0) compatible[0] else return;
const regs = try node.reg(allocator);
defer regs.deinit();
const reg = try kmem.mapDevice(regs.items[0]);
const reg_shift_bytes = node.props.get("reg-shift");
const reg_shift = if (reg_shift_bytes) |bytes| std.mem.readInt(u32, bytes[0..4], .big) else 0;
default = .{ .reg = reg.slice(u8), .reg_shift = @intCast(reg_shift) };
}
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