drm/i915/dp: cache eDP DPCD data

Cache the first 4 bytes of DPCD data in the eDP case.  It's unlikely to
change and can save us some trouble at link training time.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

2 files changed, 21 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 6d49a9f5c2b1..84e33aeececd 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -350,6 +350,7 @@ typedef struct drm_i915_private {
                 int bpp;
                 struct edp_power_seq pps;
         } edp;
+        bool no_aux_handshake;
 
         struct notifier_block lid_notifier;
 
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 944dfe199f6e..7fa828275e4a 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1724,6 +1724,26 @@ intel_dp_init(struct drm_device *dev, int output_reg)
 
         intel_dp_i2c_init(intel_dp, intel_connector, name);
 
+        /* Cache some DPCD data in the eDP case */
+        if (is_edp(intel_dp)) {
+                int ret;
+                bool was_on;
+
+                was_on = ironlake_edp_panel_on(intel_dp);
+                ret = intel_dp_aux_native_read(intel_dp, DP_DPCD_REV,
+                                               intel_dp->dpcd,
+                                               sizeof(intel_dp->dpcd));
+                if (ret == sizeof(intel_dp->dpcd)) {
+                        if (intel_dp->dpcd[0] >= 0x11)
+                                dev_priv->no_aux_handshake = intel_dp->dpcd[3] &
+                                        DP_NO_AUX_HANDSHAKE_LINK_TRAINING;
+                } else {
+                        DRM_ERROR("failed to retrieve link info\n");
+                }
+                if (!was_on)
+                        ironlake_edp_panel_off(dev);
+        }
+
         intel_encoder->hot_plug = intel_dp_hot_plug;
 
         if (is_edp(intel_dp)) {