MFi386: Attempt to reset the machine using the Reset Control register and

Fast A20 and Init register if the keyboard reset doesn't work before
resorting to a triple fault.

1 files changed, 30 insertions, 1 deletions

diff --git a/sys/amd64/amd64/vm_machdep.c b/sys/amd64/amd64/vm_machdep.c
index afe70a0..0bc3604 100644
--- a/sys/amd64/amd64/vm_machdep.c
+++ b/sys/amd64/amd64/vm_machdep.c
@@ -457,6 +457,9 @@ cpu_reset()
 static void
 cpu_reset_real()
 {
+	int b;
+
+	disable_intr();
 
 	/*
 	 * Attempt to do a CPU reset via the keyboard controller,
@@ -465,7 +468,33 @@ cpu_reset_real()
 	 */
 	outb(IO_KBD + 4, 0xFE);
 	DELAY(500000);	/* wait 0.5 sec to see if that did it */
-	printf("Keyboard reset did not work, attempting CPU shutdown\n");
+
+	/*
+	 * Attempt to force a reset via the Reset Control register at
+	 * I/O port 0xcf9.  Bit 2 forces a system reset when it is
+	 * written as 1.  Bit 1 selects the type of reset to attempt:
+	 * 0 selects a "soft" reset, and 1 selects a "hard" reset.  We
+	 * try to do a "soft" reset first, and then a "hard" reset.
+	 */
+	outb(0xcf9, 0x2);
+	outb(0xcf9, 0x6);
+	DELAY(500000);  /* wait 0.5 sec to see if that did it */
+
+	/*
+	 * Attempt to force a reset via the Fast A20 and Init register
+	 * at I/O port 0x92.  Bit 1 serves as an alternate A20 gate.
+	 * Bit 0 asserts INIT# when set to 1.  We are careful to only
+	 * preserve bit 1 while setting bit 0.  We also must clear bit
+	 * 0 before setting it if it isn't already clear.
+	 */
+	b = inb(0x92);
+	if (b != 0xff) {
+		if ((b & 0x1) != 0)
+			outb(0x92, b & 0xfe);
+		outb(0x92, b | 0x1);
+		DELAY(500000);  /* wait 0.5 sec to see if that did it */
+	}
+	printf("No known reset method worked, attempting CPU shutdown\n");
 	DELAY(1000000);	/* wait 1 sec for printf to complete */
 
 	/* Force a shutdown by unmapping entire address space. */