src/timer.zig


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const interrupt = @import("interrupt.zig");

const sys_tick_type = packed struct {
    enable: u1,
    tickint: u1,
    unused: u30,

    rvr: u32,
    cvr: u32,
    calib: u32,
};

var sys_tick: *volatile sys_tick_type = @ptrFromInt(0xE000E010);

pub var ticks_raw: u32 = 0;

pub fn initialize(freq: u32) void {
    interrupt.register(.SysTick, tick);
    sys_tick.rvr = 4000000 / 8 / freq;
    sys_tick.tickint = 1;
    sys_tick.enable = 1;
}

fn tick() void {
    ticks_raw += 1;
}

pub fn ticks() u32 {
    return @atomicLoad(u32, &ticks_raw, .acquire);
}