[Intel-gfx] [PATCH RFC] drm: i915: Don't try detecting sinks on ports already in use

[Gabriel Krisman Bertazi]

On systems where more than one connector is attached to the same port,
the HPD pin is also shared, and attaching one connector will trigger a
hotplug on every other connector on that port.  But, according to the
documentation, connectors sharing the port cannot be enabled
simultaneously, such that we can abort the detection process early if
another connector was detected succesfully.

This has the good side effect of preventing DP timeouts whenever
something else is connected to the shared port, like below:

[drm:intel_dp_aux_ch [i915]] dp_aux_ch timeout status 0x7143003f
[drm:drm_dp_dpcd_access] Too many retries, giving up. First error: -110

Since this reduces the overhead of the i915_hotplug_work_func, it may
address the following vblank misses detected by the CI:

https://bugs.freedesktop.org/show_bug.cgi?id=100215
https://bugs.freedesktop.org/show_bug.cgi?id=100558

Signed-off-by: Gabriel Krisman Bertazi <krisman at collabora.co.uk>
---
 drivers/gpu/drm/i915/intel_display.c | 26 ++++++++++++++++++++++++++
 drivers/gpu/drm/i915/intel_dp.c      |  3 +++
 drivers/gpu/drm/i915/intel_drv.h     |  1 +
 drivers/gpu/drm/i915/intel_hdmi.c    |  3 +++
 4 files changed, 33 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 85b9e2f521a0..618b5138c0c7 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -11270,6 +11270,32 @@ static bool check_digital_port_conflicts(struct drm_atomic_state *state)
 	return true;
 }
 
+bool intel_shared_digital_port_in_use(struct drm_connector *conn)
+{
+	struct drm_connector *peer;
+	struct drm_connector_list_iter iter;
+	struct intel_encoder *enc = to_intel_connector(conn)->encoder;
+	int ret = false;
+
+	drm_connector_list_iter_begin(conn->dev, &iter);
+	drm_for_each_connector_iter(peer, &iter) {
+		struct intel_encoder *peer_enc;
+
+		if (peer == conn ||
+		    peer->status != connector_status_connected)
+			continue;
+
+		peer_enc = to_intel_connector(peer)->encoder;
+		if (peer_enc->port == enc->port) {
+			ret = true;
+			break;
+		}
+	}
+	drm_connector_list_iter_end(&iter);
+
+	return ret;
+}
+
 static void
 clear_intel_crtc_state(struct intel_crtc_state *crtc_state)
 {
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 08834f74d396..0823c588575f 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -4628,6 +4628,9 @@ intel_dp_long_pulse(struct intel_connector *intel_connector)
 
 	WARN_ON(!drm_modeset_is_locked(&connector->dev->mode_config.connection_mutex));
 
+	if (intel_shared_digital_port_in_use(connector))
+		return connector_status_disconnected;
+
 	intel_display_power_get(to_i915(dev), intel_dp->aux_power_domain);
 
 	/* Can't disconnect eDP, but you can close the lid... */
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 54f3ff840812..fd5f2517bede 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -1411,6 +1411,7 @@ int vlv_force_pll_on(struct drm_i915_private *dev_priv, enum pipe pipe,
 		     const struct dpll *dpll);
 void vlv_force_pll_off(struct drm_i915_private *dev_priv, enum pipe pipe);
 int lpt_get_iclkip(struct drm_i915_private *dev_priv);
+bool intel_shared_digital_port_in_use(struct drm_connector *conn);
 
 /* modesetting asserts */
 void assert_panel_unlocked(struct drm_i915_private *dev_priv,
diff --git a/drivers/gpu/drm/i915/intel_hdmi.c b/drivers/gpu/drm/i915/intel_hdmi.c
index 6efc3cb8c471..ed4015ae7d24 100644
--- a/drivers/gpu/drm/i915/intel_hdmi.c
+++ b/drivers/gpu/drm/i915/intel_hdmi.c
@@ -1527,6 +1527,9 @@ intel_hdmi_detect(struct drm_connector *connector, bool force)
 	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
 		      connector->base.id, connector->name);
 
+	if (intel_shared_digital_port_in_use(connector))
+		return connector_status_disconnected;;
+
 	intel_display_power_get(dev_priv, POWER_DOMAIN_GMBUS);
 
 	intel_hdmi_unset_edid(connector);
-- 
2.11.0