[Intel-gfx] [PATCH] drm/i915: Check DDI max lanes after applying BXT workaround

[Matt Roper]

In commit bfb9faab8 we added a workaround for some BXT BIOS that fail to
properly initialize the DDI_A_4_LANES bit of the control register (4
lanes is the only valid configuration on BXT since there is no DDI E to
share with).  A recent patch added some additional checks on this
register bit before the workaround gets applied; this breaks eDP on BXT
in some settings.  Some minor code shuffling is all we need to restore
the workaround.

Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Fixes: 7cd87cb80 ("drm/i915: Check max number of lanes when registering DDI ports")
Signed-off-by: Matt Roper <matthew.d.roper at intel.com>
---
 drivers/gpu/drm/i915/intel_ddi.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index 75b57a8..6ac80cd 100644
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -3288,7 +3288,6 @@ void intel_ddi_init(struct drm_device *dev, enum port port)
 	intel_dig_port->saved_port_bits = I915_READ(DDI_BUF_CTL(port)) &
 					  (DDI_BUF_PORT_REVERSAL |
 					   DDI_A_4_LANES);
-	intel_dig_port->max_lanes = max_lanes;
 
 	/*
 	 * Bspec says that DDI_A_4_LANES is the only supported configuration
@@ -3301,9 +3300,12 @@ void intel_ddi_init(struct drm_device *dev, enum port port)
 		if (!(intel_dig_port->saved_port_bits & DDI_A_4_LANES)) {
 			DRM_DEBUG_KMS("BXT BIOS forgot to set DDI_A_4_LANES for port A; fixing\n");
 			intel_dig_port->saved_port_bits |= DDI_A_4_LANES;
+			max_lanes = 4;
 		}
 	}
 
+	intel_dig_port->max_lanes = max_lanes;
+
 	intel_encoder->type = INTEL_OUTPUT_UNKNOWN;
 	intel_encoder->crtc_mask = (1 << 0) | (1 << 1) | (1 << 2);
 	intel_encoder->cloneable = 0;
-- 
2.1.4