drm/i915/display: Handle lost primary_port across suspend

icl-dsi is dying on suspend/resume at

	RIP: 0010:icl_update_active_dpll+0x2c/0xa0 [i915]

which appears due to the loss of the time primary_port across suspend.
Protect against the potential NULL dereference by assuming
ICL_PORT_DPLL_DEFAULT unless the port is actively specified otherwise.

Fixes: 24a7bfe0c2d7 ("drm/i915: Keep the TypeC port mode fixed when the port is active")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190702140950.7069-1-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/display/intel_dpll_mgr.c b/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
index 76a2c87..f953971 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
+++ b/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
@@ -2883,21 +2883,16 @@ static void icl_update_active_dpll(struct intel_atomic_state *state,
        struct intel_crtc_state *crtc_state =
                intel_atomic_get_new_crtc_state(state, crtc);
        struct intel_digital_port *primary_port;
-       enum icl_port_dpll_id port_dpll_id;
+       enum icl_port_dpll_id port_dpll_id = ICL_PORT_DPLL_DEFAULT;
 
        primary_port = encoder->type == INTEL_OUTPUT_DP_MST ?
                enc_to_mst(&encoder->base)->primary :
                enc_to_dig_port(&encoder->base);
 
-       switch (primary_port->tc_mode) {
-       case TC_PORT_TBT_ALT:
-               port_dpll_id = ICL_PORT_DPLL_DEFAULT;
-               break;
-       case TC_PORT_DP_ALT:
-       case TC_PORT_LEGACY:
+       if (primary_port &&
+           (primary_port->tc_mode == TC_PORT_DP_ALT ||
+            primary_port->tc_mode == TC_PORT_LEGACY))
                port_dpll_id = ICL_PORT_DPLL_MG_PHY;
-               break;
-       }
 
        icl_set_active_port_dpll(crtc_state, port_dpll_id);
 }