drm/radeon/dpm: disable cac setup on SI

Disable cac setup on SI for now since it causes
strange performance level restrictions on certain
cards.  I suspect there may be issues with some of
the 64 bit fixed point double emulation that is used
to set up those parameters.  I need to double check
the math before this can be re-enabled.
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/si_dpm.c

@@ -1929,6 +1929,7 @@ static void si_initialize_powertune_defaults(struct radeon_device *rdev)
 			si_pi->cac_override = cac_override_pitcairn;
 			si_pi->powertune_data = &powertune_data_pitcairn;
 			si_pi->dte_data = dte_data_pitcairn;
+			break;
 		}
 	} else if (rdev->family == CHIP_VERDE) {
 		si_pi->lcac_config = lcac_cape_verde;
@@ -2041,7 +2042,8 @@ static void si_initialize_powertune_defaults(struct radeon_device *rdev)
 	ni_pi->enable_sq_ramping = false;
 	si_pi->enable_dte = false;
 
-	if (si_pi->powertune_data->enable_powertune_by_default) {
+	/* XXX: fix me */
+	if (0/*si_pi->powertune_data->enable_powertune_by_default*/) {
 		ni_pi->enable_power_containment= true;
 		ni_pi->enable_cac = true;
 		if (si_pi->dte_data.enable_dte_by_default) {