[PATCH v3 02/20] drm/i915/dp_mst: Verify the link status always the same way

[Imre Deak <imre.deak@intel.com>]

The MST link status should be always verified from the same DPCD
registers after link training. Atm, both the legacy (0x202 - 0x205) and
the ESI (0x200C - 0x200F) link status registers are used. Use always the
latter ESI version of link status registers.

v2: Propagate error from intel_dp_read_link_status(). (Jani, Luca)

Cc: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index eb4a1c5c55714..e94fcacb95304 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -5555,6 +5555,23 @@ intel_dp_handle_hdmi_link_status_change(struct intel_dp *intel_dp)
 	}
 }
 
+static int
+intel_dp_read_link_status(struct intel_dp *intel_dp, u8 link_status[DP_LINK_STATUS_SIZE])
+{
+	int err;
+
+	memset(link_status, 0, DP_LINK_STATUS_SIZE);
+
+	if (intel_dp_mst_active_streams(intel_dp) > 0)
+		err = drm_dp_dpcd_read_data(&intel_dp->aux, DP_LANE0_1_STATUS_ESI,
+					    link_status, DP_LINK_STATUS_SIZE - 2);
+	else
+		err = drm_dp_dpcd_read_phy_link_status(&intel_dp->aux, DP_PHY_DPRX,
+						       link_status);
+
+	return err;
+}
+
 static bool
 intel_dp_needs_link_retrain(struct intel_dp *intel_dp)
 {
@@ -5577,8 +5594,7 @@ intel_dp_needs_link_retrain(struct intel_dp *intel_dp)
 	if (intel_dp->link.force_retrain)
 		return true;
 
-	if (drm_dp_dpcd_read_phy_link_status(&intel_dp->aux, DP_PHY_DPRX,
-					     link_status) < 0)
+	if (intel_dp_read_link_status(intel_dp, link_status) < 0)
 		return false;
 
 	/*
-- 
2.49.1