On PowerMac11,2 and (presumably) PowerMac12,1, we need to quiesce the

firmware in order to take over control of the SMU. Without doing this,
the firmware background process doing fan control will run amok as we
take over the system and crash the management chip.

This is limited to these two machines because our kernel is heavily
dependent on firmware accesses, and so quiescing firmware can cause
nasty problems.

sys/dev/ofw/ofw_if.m

@@ -339,6 +339,13 @@ METHOD void release {
 
 # Commands for returning control to the firmware
 
+/**
+ * @brief Turn off firmware background activities
+ */
+METHOD void quiesce {
+	ofw_t		_ofw;
+};
+
 /**
  * @brief Temporarily return control to firmware.
  */

sys/dev/ofw/ofw_standard.c

@@ -105,6 +105,7 @@ static ssize_t ofw_std_write(ofw_t ofw, ihandle_t instance, const void *addr,
 static int ofw_std_seek(ofw_t ofw, ihandle_t instance, uint64_t pos);
 static caddr_t ofw_std_claim(ofw_t ofw, void *virt, size_t size, u_int align);
 static void ofw_std_release(ofw_t ofw, void *virt, size_t size);
+static void ofw_std_quiesce(ofw_t ofw);
 static void ofw_std_enter(ofw_t ofw);
 static void ofw_std_exit(ofw_t ofw);
 
@@ -133,6 +134,7 @@ static ofw_method_t ofw_std_methods[] = {
 	OFWMETHOD(ofw_seek,			ofw_std_seek),
 	OFWMETHOD(ofw_claim,			ofw_std_claim),
 	OFWMETHOD(ofw_release,			ofw_std_release),
+	OFWMETHOD(ofw_quiesce,			ofw_std_quiesce),
 	OFWMETHOD(ofw_enter,			ofw_std_enter),
 	OFWMETHOD(ofw_exit,			ofw_std_exit),
 
@@ -730,6 +732,23 @@ ofw_std_release(ofw_t ofw, void *virt, size_t size)
  * Control transfer functions
  */
 
+/* Turn off OF background tasks */
+static void
+ofw_std_quiesce(ofw_t ofw)
+{
+	struct {
+		cell_t name;
+		cell_t nargs;
+		cell_t nreturns;
+	} args = {
+		(cell_t)"quiesce",
+		0,
+		0,
+	};
+
+	openfirmware(&args);
+}
+
 /* Suspend and drop back to the Open Firmware interface. */
 static void
 ofw_std_enter(ofw_t ofw)

sys/dev/ofw/openfirm.c

@@ -409,6 +409,15 @@ OF_release(void *virt, size_t size)
  * Control transfer functions
  */
 
+/* Turn off OF background tasks */
+void
+OF_quiesce()
+{
+
+	OFW_QUIESCE(ofw_obj);
+}
+
+
 /* Suspend and drop back to the Open Firmware interface. */
 void
 OF_enter()

sys/dev/ofw/openfirm.h

@@ -133,6 +133,7 @@ void		*OF_claim(void *virtrequest, size_t size, u_int align);
 void		OF_release(void *virt, size_t size);
 
 /* Control transfer functions */
+void		OF_quiesce(void);
 void		OF_enter(void);
 void		OF_exit(void) __attribute__((noreturn));
 

sys/powerpc/aim/ofw_machdep.c

@@ -281,6 +281,8 @@ OF_initial_setup(void *fdt_ptr, void *junk, int (*openfirm)(void *))
 boolean_t
 OF_bootstrap()
 {
+	char model[32];
+	phandle_t rootnode;
 	boolean_t status = FALSE;
 
 	mtx_init(&ofw_mutex, "open firmware", NULL, MTX_DEF);
@@ -295,6 +297,17 @@ OF_bootstrap()
 			return status;
 
 		OF_init(openfirmware);
+
+		/*
+		 * On some machines, we need to quiesce OF to turn off
+		 * background processes.
+		 */
+		rootnode = OF_finddevice("/");
+		if (OF_getprop(rootnode, "model", model, sizeof(model)) > 0) {
+			if (strcmp(model, "PowerMac11,2") == 0 ||
+			    strcmp(model, "PowerMac12,1") == 0)
+				OF_quiesce();
+		}
 	} else {
 		status = OF_install(OFW_FDT, 0);
 

sys/powerpc/ofw/ofw_real.c

@@ -106,6 +106,7 @@ static ssize_t ofw_real_write(ofw_t, ihandle_t instance, const void *addr,
 static int ofw_real_seek(ofw_t, ihandle_t instance, u_int64_t pos);
 static caddr_t ofw_real_claim(ofw_t, void *virt, size_t size, u_int align);
 static void ofw_real_release(ofw_t, void *virt, size_t size);
+static void ofw_real_quiesce(ofw_t);
 static void ofw_real_enter(ofw_t);
 static void ofw_real_exit(ofw_t);
 
@@ -133,6 +134,7 @@ static ofw_method_t ofw_real_methods[] = {
 	OFWMETHOD(ofw_seek,			ofw_real_seek),
 	OFWMETHOD(ofw_claim,			ofw_real_claim),
 	OFWMETHOD(ofw_release,			ofw_real_release),
+	OFWMETHOD(ofw_quiesce,			ofw_real_quiesce),
 	OFWMETHOD(ofw_enter,			ofw_real_enter),
 	OFWMETHOD(ofw_exit,			ofw_real_exit),
 
@@ -889,6 +891,27 @@ ofw_real_release(ofw_t ofw, void *virt, size_t size)
  * Control transfer functions
  */
 
+/* Turn off OF background tasks */
+static void
+ofw_real_quiesce(ofw_t ofw)
+{
+	vm_offset_t argsptr;
+	struct {
+		cell_t name;
+		cell_t nargs;
+		cell_t nreturns;
+	} args;
+
+	args.name = (cell_t)(uintptr_t)"quiesce";
+	args.nargs = 0;
+	args.nreturns = 0;
+
+	ofw_real_start();
+	argsptr = ofw_real_map(&args, sizeof(args));
+	openfirmware((void *)argsptr);
+	ofw_real_stop();
+}
+
 /* Suspend and drop back to the Open Firmware interface. */
 static void
 ofw_real_enter(ofw_t ofw)