drm/i915/bxt: WA for swapped HPD pins in A stepping

WA for BXT A0/A1, where DDIB's HPD pin is swapped to DDIA, so enabling
DDIA HPD pin in place of DDIB.

v2: For DP, irq_port is used to determine the encoder instead of
hpd_pin and removing the edp HPD logic because port A HPD is not
present(Imre)
v3: Rebased on top of Imre's patchset for enabling HPD on PORT A.
Added hpd_pin swapping for intel_dp_init_connector, setting encoder
for PORT_A as per the WA in irq_port (Imre)
v4: Dont enable interrupt for edp, also reframe the description (Siva)
v5: Don’t check for PORT_A in intel_ddi_init to update dig_port,
instead avoid setting hpd_pin itself (Imre)

Signed-off-by: Sonika Jindal <sonika.jindal@intel.com>
Reviewed-by: Sivakumar Thulasimani <sivakumar.thulasimani@intel.com>
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 54e9b53..a028246 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -5876,6 +5876,8 @@
 		break;
 	case PORT_B:
 		intel_encoder->hpd_pin = HPD_PORT_B;
+		if (IS_BROXTON(dev_priv) && (INTEL_REVID(dev) < BXT_REVID_B0))
+			intel_encoder->hpd_pin = HPD_PORT_A;
 		break;
 	case PORT_C:
 		intel_encoder->hpd_pin = HPD_PORT_C;