drm/i915: Warn if stealing power sequencer from an active eDP port

eDP ports need the power seqeuncer whenever the port is active. Warn if
we accidentally steal the power sequener from an active eDP port. This
should not happen unless there's a bug somewhere else, but it's best to
scream loudly if it happens to help with debugging.

Note that this only checks for active pipes and not for enabled pipes
which are turned off with dpms. Which means we might run the risk that
the pps might get stolen and we can't reacquire one when enabling the
pipe again with dpms on. But on current platforms that's impossible
since we only support two edp ports with just two panel power
sequencers. So a more elaborate scheme which reserves the pps even
when the pipe is inactive isn't required.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
[danvet: Summarize my discussion with Ville about dpms on/off issues.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 9db977b475f8e42b71d9292c6969ba436c9b5d56..90d752d5d6ea7758f8a6fa1d3bcc4c4ab4531764 100644 (file)
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -2728,6 +2728,10 @@ static void vlv_steal_power_sequencer(struct drm_device *dev,
                DRM_DEBUG_KMS("stealing pipe %c power sequencer from port %c\n",
                              pipe_name(pipe), port_name(port));
 
+               WARN(encoder->connectors_active,
+                    "stealing pipe %c power sequencer from active eDP port %c\n",
+                    pipe_name(pipe), port_name(port));
+
                /* make sure vdd is off before we steal it */
                vlv_detach_power_sequencer(intel_dp);
        }