[Intel-gfx] [PATCH] drm/i915/ilk: Don't attempt to register eDP if LVDS was detected

[Imre Deak]

Atm on ILK we attempt to detect if eDP is present even if LVDS was
already detected and an encoder for it was registered. This involves
trying to read out the eDP EDID, which in turn needs the same power
sequencer that LVDS uses. Poking at the VDD line at an unexpected time
may or may not interfere with the LVDS panel, but it's probably safer to
prevent this.  Registering both an LVDS and an eDP connector would also
present a similar problem accessing the shared PPS at any point later in
an unexpected way.

This was caught by CI with the PPS sanity checks in place and the
initial eDP EDID readout waiting for the panel power cycle timeout
without the PPS registers being initialized. To solve this latter
problem move PPS register init earlier before the first use of the
PPS.

CC: Ville Syrjälä <ville.syrjala at linux.intel.com>
Signed-off-by: Imre Deak <imre.deak at intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index be08351..fe543d7 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -5316,8 +5316,22 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
 	if (!is_edp(intel_dp))
 		return true;
 
+	/*
+	 * On ILK we may get here with LVDS already registered. Since the
+	 * driver uses the only internal power sequencer available for both
+	 * eDP and LVDS bail out early in this case to prevent interfering
+	 * with an already powered-on LVDS power sequencer.
+	 */
+	for_each_intel_encoder(dev, intel_encoder) {
+		if (intel_encoder->type == INTEL_OUTPUT_LVDS) {
+			DRM_INFO("LVDS was detected, not registering eDP\n");
+			return false;
+		}
+	}
+
 	pps_lock(intel_dp);
 	intel_edp_panel_vdd_sanitize(intel_dp);
+	intel_dp_init_panel_power_sequencer_registers(dev, intel_dp);
 	pps_unlock(intel_dp);
 
 	/* Cache DPCD and EDID for edp. */
@@ -5334,11 +5348,6 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
 		return false;
 	}
 
-	/* We now know it's not a ghost, init power sequence regs. */
-	pps_lock(intel_dp);
-	intel_dp_init_panel_power_sequencer_registers(dev, intel_dp);
-	pps_unlock(intel_dp);
-
 	mutex_lock(&dev->mode_config.mutex);
 	edid = drm_get_edid(connector, &intel_dp->aux.ddc);
 	if (edid) {
-- 
2.5.0