feat: pit timer

9 files changed, 72 insertions, 11 deletions

diff --git a/boot/boot.zig b/boot/boot.zig
index 108afc8..8f8c7fe 100644
--- a/boot/boot.zig
+++ b/boot/boot.zig
@@ -10,6 +10,7 @@ const vmm = @import("vmm.zig");
 const user = @import("user.zig");
 const elf = @import("elf.zig");
 const keyboard = @import("keyboard.zig");
+const timer = @import("timer.zig");
 const bridge = @import("bridge");
 
 // We need a panic handler otherwise zig won't be happy,
@@ -166,11 +167,16 @@ export fn _start() callconv(.c) noreturn {
     // the cli/pop/sti-hlt bullshit closes the lost-wakeup race (a key
     // arriving between "queue empty" and hlt would otherwise sit until
     // the next keypress)
+    var last_ticks: u64 = 0;
     while (true) {
         asm volatile ("cli");
         if (keyboard.pop()) |sc| {
             asm volatile ("sti");
             bridge.onKey(sc);
+        } else if (timer.now() != last_ticks) {
+            last_ticks = timer.now();
+            asm volatile ("sti");
+            bridge.onTick(last_ticks);
         } else {
             asm volatile ("sti; hlt");
         }
diff --git a/boot/idt.zig b/boot/idt.zig
index fda5b9d..19afa6b 100644
--- a/boot/idt.zig
+++ b/boot/idt.zig
@@ -8,6 +8,7 @@ const gdt = @import("gdt.zig");
 const serial = @import("serial.zig");
 const pic = @import("pic.zig");
 const keyboard = @import("keyboard.zig");
+const timer = @import("timer.zig");
 
 // 64bit interrupt gate
 const Gate = packed struct {
@@ -219,6 +220,7 @@ export fn irqCommon() callconv(.naked) void {
 
 export fn irqDispatch(frame: *Frame) callconv(.c) void {
     switch (frame.vector) {
+        pic.MASTER_OFFSET + 0 => timer.onIrq(), // IRQ0: PIT
         pic.MASTER_OFFSET + 1 => keyboard.onIrq(), // IRQ1: keyboard
         else => {},
     }
@@ -242,8 +244,10 @@ pub fn setGate(vector: u8, handler: u64, dpl: u2) void {
 // fill the exception vectors and load the IDT
 pub fn init() void {
     inline for (0..32) |v| setGate(v, @intFromPtr(&stub(v)), 0);
+    // IRQ0 (PIT) -> vector 0x20
     // IRQ1 (keyboard) -> vector 0x21
-    // the PIC is remapped separately in boot.
+    // the PIC is remapped separately in boot
+    setGate(pic.MASTER_OFFSET + 0, @intFromPtr(&irqStub(pic.MASTER_OFFSET + 0)), 0);
     setGate(pic.MASTER_OFFSET + 1, @intFromPtr(&irqStub(pic.MASTER_OFFSET + 1)), 0);
     idtr = .{ .limit = @sizeOf(@TypeOf(idt)) - 1, .base = @intFromPtr(&idt) };
     asm volatile ("lidt (%[idtr])"
diff --git a/boot/limine.zig b/boot/limine.zig
index f1ed158..3d18b31 100644
--- a/boot/limine.zig
+++ b/boot/limine.zig
@@ -1,5 +1,5 @@
-// Limine scans the loaded image for these magic numbers, BaseRevision is 
-// a handshake, essentially we ask limine for rev 3, and if it supports it, 
+// Limine scans the loaded image for these magic numbers, BaseRevision is
+// a handshake, essentially we ask limine for rev 3, and if it supports it,
 // limine zeros it out
 pub const BaseRevision = extern struct {
     magic0: u64 = 0xf9562b2d5c95a6c8,
@@ -11,7 +11,7 @@ pub const BaseRevision = extern struct {
     }
 };
 
-// bracketing markers, they are pretty optional but when we add proper 
+// bracketing markers, they are pretty optional but when we add proper
 // limine requests, having these here comes handy
 pub const RequestsStartMarker = extern struct {
     m0: u64 = 0xf6b8f4b39de7d1ae,
diff --git a/boot/pmm.zig b/boot/pmm.zig
index 71d132e..0c4bdda 100644
--- a/boot/pmm.zig
+++ b/boot/pmm.zig
@@ -20,10 +20,10 @@ var hhdm_offset: u64 = 0;
 // reached through the HHDM, so it's just a normal slice we write through.
 var bitmap: []u8 = &[_]u8{};
 
-var total_frames: usize = 0;  // frames the bitmap can index (up to highest usable end)
+var total_frames: usize = 0; // frames the bitmap can index (up to highest usable end)
 var usable_frames: usize = 0; // frames that started free
-var free_frames: usize = 0;   // frames currently free
-var next_hint: usize = 0;     // where to start the next alloc scan
+var free_frames: usize = 0; // frames currently free
+var next_hint: usize = 0; // where to start the next alloc scan
 
 pub fn physToVirt(phys: u64) u64 {
     return phys + hhdm_offset;
@@ -95,7 +95,7 @@ pub fn init(hhdm: *const limine.HhdmResponse, memmap: *const limine.MemoryMapRes
     //
     // WARNING: never hand out a physical-null address
     //
-    // unlike marking a region free, here we round the END UP so a partial 
+    // unlike marking a region free, here we round the END UP so a partial
     // last frame the bitmap spills into still gets reserved
     {
         const start = storage_base / PAGE_SIZE;
@@ -136,7 +136,7 @@ pub fn alloc() ?u64 {
 
 // hand out n contiguous physical frames cause the heap needs one flat buffer, and a
 // single usable region is contiguous in physical space, so this just finds a
-// run of n free bits. 
+// run of n free bits.
 // NOTE: returns the base physical address of the run
 pub fn allocContig(n: usize) ?u64 {
     if (n == 0) return null;
diff --git a/boot/timer.zig b/boot/timer.zig
new file mode 100644
index 0000000..4569d6a
--- /dev/null
+++ b/boot/timer.zig
@@ -0,0 +1,17 @@
+// PIT channel 0 tick counter
+// configuring the PIT itself (outb to 0x43/0x40) is done in revo (kernel
+// `pit_init`), since it's just port writes the VM can drive
+
+var ticks: u64 = 0;
+
+// called from the IRQ0 handler
+pub fn onIrq() void {
+    const t: *volatile u64 = &ticks;
+    t.* +%= 1;
+}
+
+// called from the event loop
+pub fn now() u64 {
+    const t: *volatile u64 = &ticks;
+    return t.*;
+}
diff --git a/bridge/bridge.zig b/bridge/bridge.zig
index 8786f20..a8a2243 100644
--- a/bridge/bridge.zig
+++ b/bridge/bridge.zig
@@ -496,3 +496,10 @@ fn flushConsole(vm: *revo.VM) void {
     if (f.asFunction() == null) return;
     _ = vm.callFunctionParts(f, null, &.{}, null) catch {};
 }
+
+pub fn onTick(ticks: u64) void {
+    const vm = g_vm orelse return;
+    const cb = vm.getGlobal("on_tick") orelse return;
+    if (cb.asFunction() == null) return;
+    _ = vm.callFunctionParts(cb, null, &[_]revo.Value{revo.Value.new.num(ticks)}, null) catch {};
+}
diff --git a/kernel/console.rv b/kernel/console.rv
index a894141..a949cd2 100644
--- a/kernel/console.rv
+++ b/kernel/console.rv
@@ -3,7 +3,7 @@ const FH = 16           # glyph height in pixels (8x16 VGA bitmap font)
 const FG = 0xd0d0d0
 const CON_BG = 0x101018
 
-global con = { col = 0, row = 0, scale = 1 }
+global con = { col = 0, row = 0, scale = 1, cur_on = :true, blink = 0 }
 
 # cell size in pixels at the current zoom. named cell_* (not cw/ch) so they don't
 # collide with draw_glyph's `ch` character parameter.
@@ -65,5 +65,19 @@ global flush_console = fn() do
     con_putc(string.of_ascii(c))
     c = serial_next()
   end
+  # after any output the cursor is solid at the new head restart the blink phase
+  con.cur_on = :true
+  con.blink = 0
   cursor_paint(CUR)
 end
+
+# the PIT fires ~100x/sec
+# blink the cursor every 50 ticks (~2 Hz)
+global on_tick = fn(t) do
+  con.blink += 1
+  if con.blink >= 50 do
+    con.blink = 0
+    con.cur_on = not con.cur_on
+    cursor_paint(if con.cur_on CUR else CON_BG)
+  end
+end
diff --git a/kernel/input.rv b/kernel/input.rv
index fde962d..d069521 100644
--- a/kernel/input.rv
+++ b/kernel/input.rv
@@ -14,6 +14,15 @@ fn pic_remap() do
 end
 fn pic_unmask(line) outb(0x21, inb(0x21) band (255 bxor (1 shl line)))
 
+# 8253/8254 PIT channel 0, mode 3 (square wave)
+# divisor 11931 -> ~100 Hz (1193182 / 11931)
+# the ISR just counts ticks
+fn pit_init() do
+  outb(0x43, 0x36)
+  outb(0x40, 11931 band 0xff)
+  outb(0x40, (11931 shr 8) band 0xff)
+end
+
 # she stroke my keys till i handle
 # no fr this is just a key stroke handler
 global sh = { line = "", shift = :false }
diff --git a/kernel/main.rv b/kernel/main.rv
index d3f1b23..35413ef 100644
--- a/kernel/main.rv
+++ b/kernel/main.rv
@@ -1,6 +1,10 @@
 # kmain
 pic_remap()
-pic_unmask(1)
+pit_init()
+
+pic_unmask(0)   # PIT      (IRQ0) -> cursor blink / uptime
+pic_unmask(1)   # keyboard (IRQ1)
+
 cmd_clear()
 puts("revel shell, live in revo. type `help`\n> ")
 flush_console()