From 0527ef090e4a5ff2dd8dc32170d505c44ee015fa Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Tue, 18 Nov 2025 16:05:25 -0500
Subject: kern/amd64: lapic: Add Local APIC timer interface

This commit adds an interface to perform a oneshot operation with the
Local APIC timer as well as providing a stub interrupt service routine
for it.

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 sys/arch/amd64/cpu/idt.S   |  9 +++++++++
 sys/arch/amd64/cpu/lapic.c | 24 ++++++++++++++++++++++++
 sys/inc/arch/amd64/lapic.h |  7 +++++++
 3 files changed, 40 insertions(+)

(limited to 'sys')

diff --git a/sys/arch/amd64/cpu/idt.S b/sys/arch/amd64/cpu/idt.S
index c430a44..729d958 100644
--- a/sys/arch/amd64/cpu/idt.S
+++ b/sys/arch/amd64/cpu/idt.S
@@ -306,6 +306,15 @@ page_fault:
     jmp 1b
     hlt
 
+    .globl lapic_tmr_isr
+lapic_tmr_isr:
+    KFENCE
+    push_frame 0x81
+    nop
+    pop_frame 0x81
+    KFENCE
+    iretq
+
     .section .data
     .align 8
 IDT:
diff --git a/sys/arch/amd64/cpu/lapic.c b/sys/arch/amd64/cpu/lapic.c
index acf2573..076ddd3 100644
--- a/sys/arch/amd64/cpu/lapic.c
+++ b/sys/arch/amd64/cpu/lapic.c
@@ -43,6 +43,7 @@
 #include <md/i8254.h>
 #include <md/cpuid.h>
 #include <md/msr.h>
+#include <md/idt.h>
 
 #define dtrace(fmt, ...) trace("lapic: " fmt, ##__VA_ARGS__)
 
@@ -82,6 +83,7 @@
 /* Accessed via RDMSR/WRMSR */
 #define X2APIC_MSR_BASE 0x00000800
 
+extern void lapic_tmr_isr(void);
 static struct acpi_madt *madt;
 
 /*
@@ -337,6 +339,17 @@ lapic_enable(struct mcb *mcb)
     lapic_write(mcb, LAPIC_REG_SVR, svr | 0xFF);
 }
 
+static void
+lapic_timer_oneshot(struct mcb *mcb, size_t count)
+{
+    if (mcb == NULL) {
+        return;
+    }
+
+    lapic_tmr_enable(mcb, LAPIC_TMR_ONESHOT);
+    lapic_write(mcb, LAPIC_REG_TICR, count);
+}
+
 uint32_t
 lapic_read_id(struct mcb *mcb)
 {
@@ -349,6 +362,16 @@ lapic_read_id(struct mcb *mcb)
     }
 }
 
+void
+lapic_oneshot_usec(struct mcb *mcb, size_t usec)
+{
+    if (mcb == NULL) {
+        return;
+    }
+
+    lapic_timer_oneshot(mcb, mcb->lapic_tmr_freq / 1000000);
+}
+
 void
 lapic_init(void)
 {
@@ -375,4 +398,5 @@ lapic_init(void)
 
     lapic_enable(mcb);
     mcb->lapic_tmr_freq = lapic_tmr_clbr(mcb);
+    idt_set_gate(LAPIC_TMR_VEC, INT_GATE, (uintptr_t)lapic_tmr_isr, 0);
 }
diff --git a/sys/inc/arch/amd64/lapic.h b/sys/inc/arch/amd64/lapic.h
index 35ba778..d22a560 100644
--- a/sys/inc/arch/amd64/lapic.h
+++ b/sys/inc/arch/amd64/lapic.h
@@ -31,6 +31,7 @@
 #define _MACHINE_LAPIC_H_ 1
 
 #include <sys/types.h>
+#include <lib/stdbool.h>
 #include <mu/cpu.h>
 
 #define LAPIC_TMR_VEC 0x81
@@ -90,6 +91,12 @@ struct lapic_ipi {
     uint8_t logical_dest : 1;
 };
 
+/*
+ * Put the local APIC timer in one shot mode and fire it
+ * off
+ */
+void lapic_oneshot_usec(struct mcb *mcb, size_t usec);
+
 /*
  * Read the current local APIC id
  */
-- 
cgit v1.2.3