From 22a40088f0d2d17d680ce5d288a3ece73e20c571 Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Sun, 12 Oct 2025 15:52:00 -0400
Subject: kern/amd64: reboot: Add Intel PCH RST_CNT method

Introduces support for platform reset via the RST_CNT control register
on Intel chipsets that support it.

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 src/sys/arch/amd64/os/os_reboot.c | 42 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

(limited to 'src/sys/arch/amd64/os')

diff --git a/src/sys/arch/amd64/os/os_reboot.c b/src/sys/arch/amd64/os/os_reboot.c
index 3ed82af..2e6387c 100644
--- a/src/sys/arch/amd64/os/os_reboot.c
+++ b/src/sys/arch/amd64/os/os_reboot.c
@@ -30,6 +30,7 @@
 #include <sys/types.h>
 #include <sys/reboot.h>
 #include <sys/cdefs.h>
+#include <sys/cpuvar.h>
 #include <os/reboot.h>
 #include <machine/pio.h>
 
@@ -39,12 +40,48 @@
 #define I8042_REBOOT 0
 #endif  /* __I8042_REBOOT */
 
+static void
+intel_reset(struct mdcore *mdcore)
+{
+    /*
+     * Some intel platform controller hubs allow a
+     * reset via a special RST_CNT control register,
+     * perform a CPU reset with SYS_RST and RST_CPU.
+     */
+    if (mdcore->family == 0x06) {
+        outb(0xCF9, 3 << 1);
+    }
+}
+
+/*
+ * Perform platform specific reset methods
+ *
+ * @core: Current core for platform identification
+ */
+static void
+platform_reset(struct pcore *core)
+{
+    struct mdcore *mdcore;
+
+    if (core == NULL) {
+        return;
+    }
+
+    mdcore = &core->md;
+    switch (mdcore->vendor) {
+    case CPU_VENDOR_INTEL:
+        intel_reset(mdcore);
+        break;
+    }
+}
+
 /*
  * Actual reboot core
  */
 __dead static void
 __reboot(void)
 {
+    struct pcore *core;
     void *dmmy_null = NULL;
 
     /*
@@ -55,6 +92,11 @@ __reboot(void)
         outb(0x64, 0xFE);
     }
 
+    /* Try platform specific methods */
+    core = this_core();
+    if (core != NULL) {
+        platform_reset(core);
+    }
 
     /*
      * If somehow nothing we've tried worked, be very
-- 
cgit v1.2.3