From 034e43c6c0dc7e70a6edc96987758237cb92f0cd Mon Sep 17 00:00:00 2001
From: =?utf8?q?Ville=20Syrj=C3=A4l=C3=A4?= <ville.syrjala@linux.intel.com>
Date: Thu, 16 Oct 2014 21:27:28 +0300
Subject: [PATCH] drm/i915: Warn if stealing power sequencer from an active eDP
 port
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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>
---
 drivers/gpu/drm/i915/intel_dp.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 9db977b475f8..90d752d5d6ea 100644
--- 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);
 	}
-- 
2.20.1