[PATCH 1/3] drm: Add a new connector atomic property for link status

[PATCH 1/3] drm: Add a new connector atomic property for link status

[Manasi Navare]

At the time userspace does setcrtc, we've already promised the mode
would work. The promise is based on the theoretical capabilities of
the link, but it's possible we can't reach this in practice. The DP
spec describes how the link should be reduced, but we can't reduce
the link below the requirements of the mode. Black screen follows.

One idea would be to have setcrtc return a failure. However, it
already should not fail as the atomic checks have passed. It would
also conflict with the idea of making setcrtc asynchronous in the
future, returning before the actual mode setting and link training.

Another idea is to train the link "upfront" at hotplug time, before
pruning the mode list, so that we can do the pruning based on
practical not theoretical capabilities. However, the changes for link
training are pretty drastic, all for the sake of error handling and
DP compliance, when the most common happy day scenario is the current
approach of link training at mode setting time, using the optimal
parameters for the mode. It is also not certain all hardware could do
this without the pipe on; not even all our hardware can do this. Some
of this can be solved, but not trivially.

Both of the above ideas also fail to address link degradation *during*
operation.

The solution is to add a new "link-status" connector property in order
to address link training failure in a way that:
a) changes the current happy day scenario as little as possible, to
avoid regressions, b) can be implemented the same way by all drm
drivers, c) is still opt-in for the drivers and userspace, and opting
out doesn't regress the user experience, d) doesn't prevent drivers
from implementing better or alternate approaches, possibly without
userspace involvement. And, of course, handles all the issues presented.
In the usual happy day scenario, this is always "good". If something
fails during or after a mode set, the kernel driver can set the link
status to "bad" and issue a hotplug uevent for userspace to have it
re-check the valid modes through GET_CONNECTOR IOCTL, and try modeset
again. If the theoretical capabilities of the link can't be reached,
the mode list is trimmed based on that.

v4:
* Add comments in kernel-doc format (Daniel Vetter)
* Update the kernel-doc for link-status (Sean Paul)
v3:
* Fixed a build error (Jani Saarinen)
v2:
* Removed connector->link_status (Daniel Vetter)
* Set connector->state->link_status in drm_mode_connector_set_link_status_property
(Daniel Vetter)
* Set the connector_changed flag to true if connector->state->link_status changed.
* Reset link_status to GOOD in update_output_state (Daniel Vetter)
* Never allow userspace to set link status from Good To Bad (Daniel Vetter)

Acked-by: Tony Cheng <tony.cheng@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
---
 drivers/gpu/drm/drm_atomic.c        | 10 +++++++
 drivers/gpu/drm/drm_atomic_helper.c |  8 ++++++
 drivers/gpu/drm/drm_connector.c     | 54 ++++++++++++++++++++++++++++++++++++-
 include/drm/drm_connector.h         | 19 +++++++++++++
 include/drm/drm_mode_config.h       |  5 ++++
 include/uapi/drm/drm_mode.h         |  4 +++
 6 files changed, 99 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 89737e4..990f013 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -1087,6 +1087,14 @@ int drm_atomic_connector_set_property(struct drm_connector *connector,
 		 * now?) atomic writes to DPMS property:
 		 */
 		return -EINVAL;
+	} else if (property == config->link_status_property) {
+		/* Never downgrade from GOOD to BAD on userspace's request here,
+		 * only hw issues can do that.
+		 */
+		if (state->link_status == DRM_LINK_STATUS_GOOD)
+			return 0;
+		state->link_status = val;
+		return 0;
 	} else if (connector->funcs->atomic_set_property) {
 		return connector->funcs->atomic_set_property(connector,
 				state, property, val);
@@ -1135,6 +1143,8 @@ static void drm_atomic_connector_print_state(struct drm_printer *p,
 		*val = (state->crtc) ? state->crtc->base.id : 0;
 	} else if (property == config->dpms_property) {
 		*val = connector->dpms;
+	} else if (property == config->link_status_property) {
+		*val = state->link_status;
 	} else if (connector->funcs->atomic_get_property) {
 		return connector->funcs->atomic_get_property(connector,
 				state, property, val);
diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 494680c..962ed66 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -519,6 +519,13 @@ static int handle_conflicting_encoders(struct drm_atomic_state *state,
 					       connector_state);
 		if (ret)
 			return ret;
+		if (connector->state->crtc) {
+			crtc_state = drm_atomic_get_existing_crtc_state(state,
+									connector->state->crtc);
+			if (connector->state->link_status !=
+			    connector_state->link_status)
+				crtc_state->connectors_changed = true;
+		}
 	}
 
 	/*
@@ -2258,6 +2265,7 @@ static int update_output_state(struct drm_atomic_state *state,
 								NULL);
 			if (ret)
 				return ret;
+			conn_state->link_status = DRM_LINK_STATUS_GOOD;
 		}
 	}
 
diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
index 5a45262..8902367 100644
--- a/drivers/gpu/drm/drm_connector.c
+++ b/drivers/gpu/drm/drm_connector.c
@@ -243,6 +243,10 @@ int drm_connector_init(struct drm_device *dev,
 	drm_object_attach_property(&connector->base,
 				      config->dpms_property, 0);
 
+	drm_object_attach_property(&connector->base,
+				   config->link_status_property,
+				   0);
+
 	if (drm_core_check_feature(dev, DRIVER_ATOMIC)) {
 		drm_object_attach_property(&connector->base, config->prop_crtc_id, 0);
 	}
@@ -506,6 +510,12 @@ const char *drm_get_subpixel_order_name(enum subpixel_order order)
 };
 DRM_ENUM_NAME_FN(drm_get_dpms_name, drm_dpms_enum_list)
 
+static const struct drm_prop_enum_list drm_link_status_enum_list[] = {
+	{ DRM_MODE_LINK_STATUS_GOOD, "Good" },
+	{ DRM_MODE_LINK_STATUS_BAD, "Bad" },
+};
+DRM_ENUM_NAME_FN(drm_get_link_status_name, drm_link_status_enum_list)
+
 /**
  * drm_display_info_set_bus_formats - set the supported bus formats
  * @info: display info to store bus formats in
@@ -625,7 +635,11 @@ int drm_display_info_set_bus_formats(struct drm_display_info *info,
  * 	tiling and virtualize both &drm_crtc and &drm_plane if needed. Drivers
  * 	should update this value using drm_mode_connector_set_tile_property().
  * 	Userspace cannot change this property.
- *
+ * link-status:
+ *      Connector link-status property to indicate the status of link. The default
+ *      value of link-status is "GOOD". If something fails during or after modeset,
+ *      the kernel driver may set this to "BAD" and issue a hotplug uevent. Drivers
+ *      should update this value using drm_mode_connector_set_link_status_property().
  * Connectors also have one standardized atomic property:
  *
  * CRTC_ID:
@@ -666,6 +680,13 @@ int drm_connector_create_standard_properties(struct drm_device *dev)
 		return -ENOMEM;
 	dev->mode_config.tile_property = prop;
 
+	prop = drm_property_create_enum(dev, 0, "link-status",
+					drm_link_status_enum_list,
+					ARRAY_SIZE(drm_link_status_enum_list));
+	if (!prop)
+		return -ENOMEM;
+	dev->mode_config.link_status_property = prop;
+
 	return 0;
 }
 
@@ -995,6 +1016,37 @@ int drm_mode_connector_update_edid_property(struct drm_connector *connector,
 }
 EXPORT_SYMBOL(drm_mode_connector_update_edid_property);
 
+/**
+ * drm_mode_connector_set_link_status_property - Set link status property of a connector
+ * @connector: drm connector
+ * @link_status: new value of link status property (0: Good, 1: Bad)
+ *
+ * In usual working scenario, this link status property will always be set to
+ * "GOOD". If something fails during or after a mode set, the kernel driver
+ * may set this link status property to "BAD". The caller then needs to send a
+ * hotplug uevent for userspace to re-check the valid modes through
+ * GET_CONNECTOR_IOCTL and retry modeset.
+ *
+ * Note: Drivers cannot rely on userspace to support this property and
+ * issue a modeset. As such, they may choose to handle issues (like
+ * re-training a link) without userspace's intervention.
+ *
+ * The reason for adding this property is to handle link training failures, but
+ * it is not limited to DP or link training. For example, if we implement
+ * asynchronous setcrtc, this property can be used to report any failures in that.
+ */
+void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
+						 uint64_t link_status)
+{
+	struct drm_device *dev = connector->dev;
+
+	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
+	connector->state->link_status = link_status;
+	drm_modeset_unlock(&dev->mode_config.connection_mutex);
+
+}
+EXPORT_SYMBOL(drm_mode_connector_set_link_status_property);
+
 int drm_mode_connector_set_obj_prop(struct drm_mode_object *obj,
 				    struct drm_property *property,
 				    uint64_t value)
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index 34f9741..53c5f70 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -90,6 +90,17 @@ enum subpixel_order {
 };
 
 /**
+ * enum drm_link_status - connector's link_status property value
+ *
+ * This enum is used as the connector's link status property value.
+ * It is set to the values defined in uapi.
+ */
+enum drm_link_status {
+	DRM_LINK_STATUS_GOOD = DRM_MODE_LINK_STATUS_GOOD,
+	DRM_LINK_STATUS_BAD = DRM_MODE_LINK_STATUS_BAD,
+};
+
+/**
  * struct drm_display_info - runtime data about the connected sink
  *
  * Describes a given display (e.g. CRT or flat panel) and its limitations. For
@@ -213,6 +224,12 @@ struct drm_connector_state {
 
 	struct drm_encoder *best_encoder;
 
+	/**
+	 * @link_status: Connector link_status to keep track of whether link is
+	 * GOOD or BAD to notify userspace if retraining is necessary.
+	 */
+	enum drm_link_status link_status;
+
 	struct drm_atomic_state *state;
 };
 
@@ -773,6 +790,8 @@ int drm_mode_connector_set_path_property(struct drm_connector *connector,
 int drm_mode_connector_set_tile_property(struct drm_connector *connector);
 int drm_mode_connector_update_edid_property(struct drm_connector *connector,
 					    const struct edid *edid);
+void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
+						 uint64_t link_status);
 
 /**
  * struct drm_tile_group - Tile group metadata
diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
index bf9991b..86faee4 100644
--- a/include/drm/drm_mode_config.h
+++ b/include/drm/drm_mode_config.h
@@ -431,6 +431,11 @@ struct drm_mode_config {
 	 */
 	struct drm_property *tile_property;
 	/**
+	 * @link_status_property: Default connector property for link status
+	 * of a connector
+	 */
+	struct drm_property *link_status_property;
+	/**
 	 * @plane_type_property: Default plane property to differentiate
 	 * CURSOR, PRIMARY and OVERLAY legacy uses of planes.
 	 */
diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
index 728790b..309c478 100644
--- a/include/uapi/drm/drm_mode.h
+++ b/include/uapi/drm/drm_mode.h
@@ -123,6 +123,10 @@
 #define DRM_MODE_DIRTY_ON       1
 #define DRM_MODE_DIRTY_ANNOTATE 2
 
+/* Link Status options */
+#define DRM_MODE_LINK_STATUS_GOOD	0
+#define DRM_MODE_LINK_STATUS_BAD	1
+
 struct drm_mode_modeinfo {
 	__u32 clock;
 	__u16 hdisplay;
-- 
1.9.1

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[PATCH 2/3] drm/i915: Find fallback link rate/lane count

[Manasi Navare]

If link training fails, then we need to fallback to lower
link rate first and if link training fails at RBR, then
fallback to lower lane count.
This function finds the next lower link rate/lane count
value after link training failure and limits the max
link_rate and lane_count values to these fallback values.

v6:
* Cap the max link rate and lane count to the max
values obtained during fallback link training (Daniel Vetter)
v5:
* Start the fallback at the lane count value passed not
the max lane count (Jani Nikula)
v4:
* Remove the redundant variable link_train_failed
v3:
* Remove fallback_link_rate_index variable, just obtain
that using the helper intel_dp_link_rate_index (Jani Nikula)
v2:
Squash the patch that returns the link rate index (Jani Nikula)

Acked-by: Tony Cheng <tony.cheng@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c  | 59 ++++++++++++++++++++++++++++++++++++++--
 drivers/gpu/drm/i915/intel_drv.h |  4 +++
 2 files changed, 61 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 8026a83..bc1268c 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -153,12 +153,18 @@ static void vlv_steal_power_sequencer(struct drm_device *dev,
 static u8 intel_dp_max_lane_count(struct intel_dp *intel_dp)
 {
 	struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
-	u8 source_max, sink_max;
+	u8 temp, source_max, sink_max;
 
 	source_max = intel_dig_port->max_lanes;
 	sink_max = drm_dp_max_lane_count(intel_dp->dpcd);
+	temp = min(source_max, sink_max);
+	/* Limit the max value to max fallback value during link train
+	 * failure handling.
+	 */
+	if (intel_dp->fallback_lane_count)
+		return min(temp, intel_dp->fallback_lane_count);
 
-	return min(source_max, sink_max);
+	return temp;
 }
 
 /*
@@ -281,6 +287,15 @@ static int intel_dp_common_rates(struct intel_dp *intel_dp,
 	int source_len, sink_len;
 
 	sink_len = intel_dp_sink_rates(intel_dp, &sink_rates);
+	/* Limit the max sink rate to the max fallback link rate
+	 * found during link training failure handling.
+	 */
+	if (intel_dp->fallback_link_rate) {
+		int len = sink_len - 1;
+		while (len > 0 && sink_rates[len] > intel_dp->fallback_link_rate)
+			len--;
+		sink_len = len + 1;
+	}
 	source_len = intel_dp_source_rates(intel_dp, &source_rates);
 
 	return intersect_rates(source_rates, source_len,
@@ -288,6 +303,46 @@ static int intel_dp_common_rates(struct intel_dp *intel_dp,
 			       common_rates);
 }
 
+static int intel_dp_link_rate_index(struct intel_dp *intel_dp,
+				    int *common_rates, int link_rate)
+{
+	int common_len;
+	int index;
+
+	common_len = intel_dp_common_rates(intel_dp, common_rates);
+	for (index = 0; index < common_len; index++) {
+		if (link_rate == common_rates[common_len - index - 1])
+			return common_len - index - 1;
+	}
+
+	return -1;
+}
+
+int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
+					    int link_rate, uint8_t lane_count)
+{
+	int common_rates[DP_MAX_SUPPORTED_RATES] = {};
+	int common_len;
+	int link_rate_index = -1;
+
+	common_len = intel_dp_common_rates(intel_dp, common_rates);
+	link_rate_index = intel_dp_link_rate_index(intel_dp,
+						   common_rates,
+						   link_rate);
+	if (link_rate_index > 0) {
+		intel_dp->fallback_link_rate = common_rates[link_rate_index - 1];
+		intel_dp->fallback_lane_count = lane_count;
+	} else if (lane_count > 1) {
+		intel_dp->fallback_link_rate = 0;
+		intel_dp->fallback_lane_count = lane_count >> 1;
+	} else {
+		DRM_ERROR("Link Training Unsuccessful\n");
+		return -1;
+	}
+
+	return 0;
+}
+
 static enum drm_mode_status
 intel_dp_mode_valid(struct drm_connector *connector,
 		    struct drm_display_mode *mode)
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 9bbe5c5..2da3b40 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -891,6 +891,8 @@ struct intel_dp {
 	uint32_t DP;
 	int link_rate;
 	uint8_t lane_count;
+	int fallback_link_rate;
+	uint8_t fallback_lane_count;
 	uint8_t sink_count;
 	bool link_mst;
 	bool has_audio;
@@ -1393,6 +1395,8 @@ bool intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
 void intel_dp_set_link_params(struct intel_dp *intel_dp,
 			      int link_rate, uint8_t lane_count,
 			      bool link_mst);
+int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
+					    int link_rate, uint8_t lane_count);
 void intel_dp_start_link_train(struct intel_dp *intel_dp);
 void intel_dp_stop_link_train(struct intel_dp *intel_dp);
 void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode);
-- 
1.9.1

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[PATCH 3/3] drm/i915: Implement Link Rate fallback on Link training failure

[Manasi Navare]

If link training at a link rate optimal for a particular
mode fails during modeset's atomic commit phase, then we
let the modeset complete and then retry. We save the link rate
value at which link training failed, update the link status property
to "BAD" and use a lower link rate to prune the modes. It will redo
the modeset on the current mode at lower link rate or if the current
mode gets pruned due to lower link constraints then, it will send a
hotplug uevent for userspace to handle it.

This is also required to pass DP CTS tests 4.3.1.3, 4.3.1.4,
4.3.1.6.

v9:
* Use the trimmed max values of link rate/lane count based on
link train fallback (Daniel Vetter)
v8:
* Set link_status to BAD first and then call mode_valid (Jani Nikula)
v7:
Remove the redundant variable in previous patch itself
v6:
* Obtain link rate index from fallback_link_rate using
the helper intel_dp_link_rate_index (Jani Nikula)
* Include fallback within intel_dp_start_link_train (Jani Nikula)
v5:
* Move set link status to drm core (Daniel Vetter, Jani Nikula)
v4:
* Add fallback support for non DDI platforms too
* Set connector->link status inside set_link_status function
(Jani Nikula)
v3:
* Set link status property to BAd unconditionally (Jani Nikula)
* Dont use two separate variables link_train_failed and link_status
to indicate same thing (Jani Nikula)
v2:
* Squashed a few patches (Jani Nikula)

Acked-by: Tony Cheng <tony.cheng@amd.com>
Acked-by: Harry Wentland <Harry.wentland@amd.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c               | 44 +++++++++++++++++++++++++++
 drivers/gpu/drm/i915/intel_dp_link_training.c | 25 +++++++++++++--
 drivers/gpu/drm/i915/intel_drv.h              |  3 ++
 3 files changed, 70 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index bc1268c..a50b6cd 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -4435,6 +4435,8 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
 		intel_dp->compliance_test_active = 0;
 		intel_dp->compliance_test_type = 0;
 		intel_dp->compliance_test_data = 0;
+		intel_dp->fallback_link_rate = 0;
+		intel_dp->fallback_lane_count = 0;
 
 		if (intel_dp->is_mst) {
 			DRM_DEBUG_KMS("MST device may have disappeared %d vs %d\n",
@@ -4526,6 +4528,13 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
 	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
 		      connector->base.id, connector->name);
 
+	/* If this is a retry due to link training failure
+	 * then do no do a full detect
+	 */
+	if (status == connector_status_connected &&
+	    intel_dp->fallback_lane_count)
+		return status;
+
 	/* If full detect is not performed yet, do a full detect */
 	if (!intel_dp->detect_done)
 		status = intel_dp_long_pulse(intel_dp->attached_connector);
@@ -5690,6 +5699,37 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
 	return false;
 }
 
+static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
+{
+	struct intel_connector *intel_connector;
+	struct drm_connector *connector;
+	struct drm_display_mode *mode;
+	bool verbose_prune = true;
+
+	intel_connector = container_of(work, typeof(*intel_connector),
+				       modeset_retry_work);
+	connector = &intel_connector->base;
+	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
+		      connector->name);
+
+	/* Grab the locks before changing connector property*/
+	mutex_lock(&connector->dev->mode_config.mutex);
+	/* Set connector link status to BAD and send a Uevent to notify
+	 * userspace to do a modeset.
+	 */
+	drm_mode_connector_set_link_status_property(connector,
+						    DRM_MODE_LINK_STATUS_BAD);
+	list_for_each_entry(mode, &connector->modes, head) {
+		mode->status = intel_dp_mode_valid(connector,
+						   mode);
+	}
+	drm_mode_prune_invalid(connector->dev, &connector->modes,
+			       verbose_prune);
+	mutex_unlock(&connector->dev->mode_config.mutex);
+	/* Send Hotplug uevent so userspace can reprobe */
+	drm_kms_helper_hotplug_event(connector->dev);
+}
+
 bool
 intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
 			struct intel_connector *intel_connector)
@@ -5702,6 +5742,10 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
 	enum port port = intel_dig_port->port;
 	int type;
 
+	/* Initialize the work for modeset in case of link train failure */
+	INIT_WORK(&intel_connector->modeset_retry_work,
+		  intel_dp_modeset_retry_work_fn);
+
 	if (WARN(intel_dig_port->max_lanes < 1,
 		 "Not enough lanes (%d) for DP on port %c\n",
 		 intel_dig_port->max_lanes, port_name(port)))
diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
index 0048b52..cb28788 100644
--- a/drivers/gpu/drm/i915/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
@@ -313,6 +313,27 @@ void intel_dp_stop_link_train(struct intel_dp *intel_dp)
 void
 intel_dp_start_link_train(struct intel_dp *intel_dp)
 {
-	intel_dp_link_training_clock_recovery(intel_dp);
-	intel_dp_link_training_channel_equalization(intel_dp);
+	struct intel_connector *intel_connector = intel_dp->attached_connector;
+
+	if (!intel_dp_link_training_clock_recovery(intel_dp))
+		goto failure_handling;
+	if (!intel_dp_link_training_channel_equalization(intel_dp))
+		goto failure_handling;
+
+	/* Reset the Link Train Values */
+	DRM_DEBUG_KMS("Link Training Passed at Link Rate = %d, Lane count = %d",
+		      intel_dp->link_rate, intel_dp->lane_count);
+	intel_dp->fallback_link_rate = 0;
+	intel_dp->fallback_lane_count = 0;
+	return;
+
+ failure_handling:
+	DRM_DEBUG_KMS("Link Training failed at link rate = %d, lane count = %d",
+		      intel_dp->link_rate, intel_dp->lane_count);
+	if (!intel_dp_get_link_train_fallback_values(intel_dp,
+						     intel_dp->link_rate,
+						     intel_dp->lane_count))
+		/* Schedule a Hotplug Uevent to userspace to start modeset */
+		schedule_work(&intel_connector->modeset_retry_work);
+	return;
 }
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 2da3b40..d95a51e 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -315,6 +315,9 @@ struct intel_connector {
 	void *port; /* store this opaque as its illegal to dereference it */
 
 	struct intel_dp *mst_port;
+
+	/* Work struct to schedule a uevent on link train failure */
+	struct work_struct modeset_retry_work;
 };
 
 struct dpll {
-- 
1.9.1

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✗ Fi.CI.BAT: warning for series starting with [1/3] drm: Add a new connector atomic property for link status

[Patchwork]

== Series Details ==

Series: series starting with [1/3] drm: Add a new connector atomic property for link status
URL   : https://patchwork.freedesktop.org/series/16150/
State : warning

== Summary ==

Series 16150v1 Series without cover letter
https://patchwork.freedesktop.org/api/1.0/series/16150/revisions/1/mbox/

Test gem_exec_suspend:
        Subgroup basic-s3:
                pass       -> DMESG-WARN (fi-skl-6700k)
Test kms_busy:
        Subgroup basic-flip-default-a:
                pass       -> DMESG-WARN (fi-skl-6700k)
        Subgroup basic-flip-default-b:
                pass       -> DMESG-WARN (fi-skl-6700k)
        Subgroup basic-flip-default-c:
                pass       -> DMESG-WARN (fi-skl-6700k)
Test kms_cursor_legacy:
        Subgroup basic-busy-flip-before-cursor-legacy:
                pass       -> DMESG-WARN (fi-skl-6700k)
        Subgroup basic-busy-flip-before-cursor-varying-size:
                pass       -> DMESG-WARN (fi-skl-6700k)
        Subgroup basic-flip-after-cursor-legacy:
                pass       -> DMESG-WARN (fi-skl-6700k)
        Subgroup basic-flip-after-cursor-varying-size:
                pass       -> DMESG-WARN (fi-skl-6700k)
        Subgroup basic-flip-before-cursor-legacy:
                pass       -> DMESG-WARN (fi-skl-6700k)
        Subgroup basic-flip-before-cursor-varying-size:
                pass       -> DMESG-WARN (fi-skl-6700k)
Test kms_flip:
        Subgroup basic-flip-vs-dpms:
                pass       -> DMESG-WARN (fi-skl-6700k)
        Subgroup basic-flip-vs-modeset:
                pass       -> DMESG-WARN (fi-skl-6700k)
        Subgroup basic-flip-vs-wf_vblank:
                pass       -> DMESG-WARN (fi-skl-6700k)
        Subgroup basic-plain-flip:
                pass       -> DMESG-WARN (fi-skl-6700k)
Test kms_frontbuffer_tracking:
        Subgroup basic:
                pass       -> DMESG-WARN (fi-skl-6700k)
Test kms_pipe_crc_basic:
        Subgroup hang-read-crc-pipe-a:
                pass       -> DMESG-WARN (fi-skl-6700k)
        Subgroup hang-read-crc-pipe-b:
                pass       -> DMESG-WARN (fi-skl-6700k)
        Subgroup hang-read-crc-pipe-c:
                pass       -> DMESG-WARN (fi-skl-6700k)
        Subgroup nonblocking-crc-pipe-a:
                pass       -> DMESG-WARN (fi-skl-6700k)
        Subgroup nonblocking-crc-pipe-a-frame-sequence:
                pass       -> DMESG-WARN (fi-skl-6700k)
        Subgroup nonblocking-crc-pipe-b:
                pass       -> DMESG-WARN (fi-skl-6700k)
        Subgroup nonblocking-crc-pipe-b-frame-sequence:
                pass       -> DMESG-WARN (fi-skl-6700k)
        Subgroup nonblocking-crc-pipe-c:
                pass       -> DMESG-WARN (fi-skl-6700k)
        Subgroup nonblocking-crc-pipe-c-frame-sequence:
                pass       -> DMESG-WARN (fi-skl-6700k)
        Subgroup read-crc-pipe-a:
                pass       -> DMESG-WARN (fi-skl-6700k)
        Subgroup read-crc-pipe-a-frame-sequence:
                pass       -> DMESG-WARN (fi-skl-6700k)
        Subgroup read-crc-pipe-b:
                pass       -> DMESG-WARN (fi-skl-6700k)
        Subgroup read-crc-pipe-b-frame-sequence:
                pass       -> DMESG-WARN (fi-skl-6700k)
        Subgroup read-crc-pipe-c:
                pass       -> DMESG-WARN (fi-skl-6700k)
        Subgroup read-crc-pipe-c-frame-sequence:
                pass       -> DMESG-WARN (fi-skl-6700k)
        Subgroup suspend-read-crc-pipe-a:
                pass       -> DMESG-WARN (fi-skl-6700k)
        Subgroup suspend-read-crc-pipe-b:
                pass       -> DMESG-WARN (fi-skl-6700k)
        Subgroup suspend-read-crc-pipe-c:
                pass       -> DMESG-WARN (fi-skl-6700k)
Test kms_setmode:
        Subgroup basic-clone-single-crtc:
                pass       -> DMESG-WARN (fi-skl-6700k)
Test pm_rpm:
        Subgroup basic-pci-d3-state:
                pass       -> DMESG-WARN (fi-skl-6700k)
        Subgroup basic-rte:
                pass       -> DMESG-WARN (fi-skl-6700k)
Test prime_vgem:
        Subgroup basic-fence-flip:
                pass       -> DMESG-WARN (fi-skl-6700k)

fi-bdw-5557u     total:245  pass:230  dwarn:0   dfail:0   fail:0   skip:15 
fi-bsw-n3050     total:245  pass:205  dwarn:0   dfail:0   fail:0   skip:40 
fi-bxt-t5700     total:245  pass:217  dwarn:0   dfail:0   fail:0   skip:28 
fi-byt-j1900     total:245  pass:217  dwarn:0   dfail:0   fail:0   skip:28 
fi-byt-n2820     total:245  pass:213  dwarn:0   dfail:0   fail:0   skip:32 
fi-hsw-4770      total:245  pass:225  dwarn:0   dfail:0   fail:0   skip:20 
fi-hsw-4770r     total:245  pass:225  dwarn:0   dfail:0   fail:0   skip:20 
fi-ilk-650       total:245  pass:192  dwarn:0   dfail:0   fail:0   skip:53 
fi-ivb-3520m     total:245  pass:223  dwarn:0   dfail:0   fail:0   skip:22 
fi-ivb-3770      total:245  pass:223  dwarn:0   dfail:0   fail:0   skip:22 
fi-kbl-7500u     total:245  pass:223  dwarn:0   dfail:0   fail:0   skip:22 
fi-skl-6260u     total:245  pass:231  dwarn:0   dfail:0   fail:0   skip:14 
fi-skl-6700hq    total:245  pass:224  dwarn:0   dfail:0   fail:0   skip:21 
WARNING: Long output truncated

41799fbb771e82427273492bfad8f2e2ae3027ef drm-tip: 2016y-11m-29d-20h-54m-07s UTC integration manifest
9eedb94 drm/i915: Implement Link Rate fallback on Link training failure
4b05a48 drm/i915: Find fallback link rate/lane count
96d4eab drm: Add a new connector atomic property for link status

== Logs ==

For more details see: https://intel-gfx-ci.01.org/CI/Patchwork_3149/
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Re: [PATCH 3/3] drm/i915: Implement Link Rate fallback on Link training failure

[Daniel Vetter]

On Tue, Nov 29, 2016 at 11:30:33PM -0800, Manasi Navare wrote:
> If link training at a link rate optimal for a particular
> mode fails during modeset's atomic commit phase, then we
> let the modeset complete and then retry. We save the link rate
> value at which link training failed, update the link status property
> to "BAD" and use a lower link rate to prune the modes. It will redo
> the modeset on the current mode at lower link rate or if the current
> mode gets pruned due to lower link constraints then, it will send a
> hotplug uevent for userspace to handle it.
> 
> This is also required to pass DP CTS tests 4.3.1.3, 4.3.1.4,
> 4.3.1.6.
> 
> v9:
> * Use the trimmed max values of link rate/lane count based on
> link train fallback (Daniel Vetter)
> v8:
> * Set link_status to BAD first and then call mode_valid (Jani Nikula)
> v7:
> Remove the redundant variable in previous patch itself
> v6:
> * Obtain link rate index from fallback_link_rate using
> the helper intel_dp_link_rate_index (Jani Nikula)
> * Include fallback within intel_dp_start_link_train (Jani Nikula)
> v5:
> * Move set link status to drm core (Daniel Vetter, Jani Nikula)
> v4:
> * Add fallback support for non DDI platforms too
> * Set connector->link status inside set_link_status function
> (Jani Nikula)
> v3:
> * Set link status property to BAd unconditionally (Jani Nikula)
> * Dont use two separate variables link_train_failed and link_status
> to indicate same thing (Jani Nikula)
> v2:
> * Squashed a few patches (Jani Nikula)
> 
> Acked-by: Tony Cheng <tony.cheng@amd.com>
> Acked-by: Harry Wentland <Harry.wentland@amd.com>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c               | 44 +++++++++++++++++++++++++++
>  drivers/gpu/drm/i915/intel_dp_link_training.c | 25 +++++++++++++--
>  drivers/gpu/drm/i915/intel_drv.h              |  3 ++
>  3 files changed, 70 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index bc1268c..a50b6cd 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -4435,6 +4435,8 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
>  		intel_dp->compliance_test_active = 0;
>  		intel_dp->compliance_test_type = 0;
>  		intel_dp->compliance_test_data = 0;
> +		intel_dp->fallback_link_rate = 0;
> +		intel_dp->fallback_lane_count = 0;

Hm, I thought we agreed on irc to just track the max link rate/lane count
at all times, instead of fallback values that sometimes are valid and
sometimes reset to 0.

Also, resetting to 0 here is wrong, since this is not the long-pulse hpd
handler. That probably also explains why you need the hack below, but not
sure.

>  
>  		if (intel_dp->is_mst) {
>  			DRM_DEBUG_KMS("MST device may have disappeared %d vs %d\n",
> @@ -4526,6 +4528,13 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
>  	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
>  		      connector->base.id, connector->name);
>  
> +	/* If this is a retry due to link training failure
> +	 * then do no do a full detect
> +	 */
> +	if (status == connector_status_connected &&
> +	    intel_dp->fallback_lane_count)
> +		return status;

That sounds very wrong. Why do we need it?

> +
>  	/* If full detect is not performed yet, do a full detect */
>  	if (!intel_dp->detect_done)
>  		status = intel_dp_long_pulse(intel_dp->attached_connector);
> @@ -5690,6 +5699,37 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
>  	return false;
>  }
>  
> +static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
> +{
> +	struct intel_connector *intel_connector;
> +	struct drm_connector *connector;
> +	struct drm_display_mode *mode;
> +	bool verbose_prune = true;
> +
> +	intel_connector = container_of(work, typeof(*intel_connector),
> +				       modeset_retry_work);
> +	connector = &intel_connector->base;
> +	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
> +		      connector->name);
> +
> +	/* Grab the locks before changing connector property*/
> +	mutex_lock(&connector->dev->mode_config.mutex);
> +	/* Set connector link status to BAD and send a Uevent to notify
> +	 * userspace to do a modeset.
> +	 */
> +	drm_mode_connector_set_link_status_property(connector,
> +						    DRM_MODE_LINK_STATUS_BAD);
> +	list_for_each_entry(mode, &connector->modes, head) {
> +		mode->status = intel_dp_mode_valid(connector,
> +						   mode);
> +	}
> +	drm_mode_prune_invalid(connector->dev, &connector->modes,
> +			       verbose_prune);

This call to drm_mode_prune_invalid is probably just to paper over a bug
in SNA - SNA violates the hotplug handling uabi by not unconditionally
reprobing. Inconsistently paper over that bug in the kernel is not good,
userspace interfaces need to be well defined. Please remove this call and
test with either UXA or -modesetting until SNA is fixed.
-Daniel

> +	mutex_unlock(&connector->dev->mode_config.mutex);
> +	/* Send Hotplug uevent so userspace can reprobe */
> +	drm_kms_helper_hotplug_event(connector->dev);
> +}
> +
>  bool
>  intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
>  			struct intel_connector *intel_connector)
> @@ -5702,6 +5742,10 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
>  	enum port port = intel_dig_port->port;
>  	int type;
>  
> +	/* Initialize the work for modeset in case of link train failure */
> +	INIT_WORK(&intel_connector->modeset_retry_work,
> +		  intel_dp_modeset_retry_work_fn);
> +
>  	if (WARN(intel_dig_port->max_lanes < 1,
>  		 "Not enough lanes (%d) for DP on port %c\n",
>  		 intel_dig_port->max_lanes, port_name(port)))
> diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
> index 0048b52..cb28788 100644
> --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
> +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
> @@ -313,6 +313,27 @@ void intel_dp_stop_link_train(struct intel_dp *intel_dp)
>  void
>  intel_dp_start_link_train(struct intel_dp *intel_dp)
>  {
> -	intel_dp_link_training_clock_recovery(intel_dp);
> -	intel_dp_link_training_channel_equalization(intel_dp);
> +	struct intel_connector *intel_connector = intel_dp->attached_connector;
> +
> +	if (!intel_dp_link_training_clock_recovery(intel_dp))
> +		goto failure_handling;
> +	if (!intel_dp_link_training_channel_equalization(intel_dp))
> +		goto failure_handling;
> +
> +	/* Reset the Link Train Values */
> +	DRM_DEBUG_KMS("Link Training Passed at Link Rate = %d, Lane count = %d",
> +		      intel_dp->link_rate, intel_dp->lane_count);
> +	intel_dp->fallback_link_rate = 0;
> +	intel_dp->fallback_lane_count = 0;
> +	return;
> +
> + failure_handling:
> +	DRM_DEBUG_KMS("Link Training failed at link rate = %d, lane count = %d",
> +		      intel_dp->link_rate, intel_dp->lane_count);
> +	if (!intel_dp_get_link_train_fallback_values(intel_dp,
> +						     intel_dp->link_rate,
> +						     intel_dp->lane_count))
> +		/* Schedule a Hotplug Uevent to userspace to start modeset */
> +		schedule_work(&intel_connector->modeset_retry_work);
> +	return;
>  }
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 2da3b40..d95a51e 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -315,6 +315,9 @@ struct intel_connector {
>  	void *port; /* store this opaque as its illegal to dereference it */
>  
>  	struct intel_dp *mst_port;
> +
> +	/* Work struct to schedule a uevent on link train failure */
> +	struct work_struct modeset_retry_work;
>  };
>  
>  struct dpll {
> -- 
> 1.9.1
> 
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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Re: [PATCH 3/3] drm/i915: Implement Link Rate fallback on Link training failure

[Chris Wilson]

On Wed, Nov 30, 2016 at 09:36:33AM +0100, Daniel Vetter wrote:
> On Tue, Nov 29, 2016 at 11:30:33PM -0800, Manasi Navare wrote:
> > If link training at a link rate optimal for a particular
> > mode fails during modeset's atomic commit phase, then we
> > let the modeset complete and then retry. We save the link rate
> > value at which link training failed, update the link status property
> > to "BAD" and use a lower link rate to prune the modes. It will redo
> > the modeset on the current mode at lower link rate or if the current
> > mode gets pruned due to lower link constraints then, it will send a
> > hotplug uevent for userspace to handle it.
> > 
> > This is also required to pass DP CTS tests 4.3.1.3, 4.3.1.4,
> > 4.3.1.6.
> > 
> > v9:
> > * Use the trimmed max values of link rate/lane count based on
> > link train fallback (Daniel Vetter)
> > v8:
> > * Set link_status to BAD first and then call mode_valid (Jani Nikula)
> > v7:
> > Remove the redundant variable in previous patch itself
> > v6:
> > * Obtain link rate index from fallback_link_rate using
> > the helper intel_dp_link_rate_index (Jani Nikula)
> > * Include fallback within intel_dp_start_link_train (Jani Nikula)
> > v5:
> > * Move set link status to drm core (Daniel Vetter, Jani Nikula)
> > v4:
> > * Add fallback support for non DDI platforms too
> > * Set connector->link status inside set_link_status function
> > (Jani Nikula)
> > v3:
> > * Set link status property to BAd unconditionally (Jani Nikula)
> > * Dont use two separate variables link_train_failed and link_status
> > to indicate same thing (Jani Nikula)
> > v2:
> > * Squashed a few patches (Jani Nikula)
> > 
> > Acked-by: Tony Cheng <tony.cheng@amd.com>
> > Acked-by: Harry Wentland <Harry.wentland@amd.com>
> > Cc: Jani Nikula <jani.nikula@linux.intel.com>
> > Cc: Daniel Vetter <daniel.vetter@intel.com>
> > Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> > Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_dp.c               | 44 +++++++++++++++++++++++++++
> >  drivers/gpu/drm/i915/intel_dp_link_training.c | 25 +++++++++++++--
> >  drivers/gpu/drm/i915/intel_drv.h              |  3 ++
> >  3 files changed, 70 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > index bc1268c..a50b6cd 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -4435,6 +4435,8 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
> >  		intel_dp->compliance_test_active = 0;
> >  		intel_dp->compliance_test_type = 0;
> >  		intel_dp->compliance_test_data = 0;
> > +		intel_dp->fallback_link_rate = 0;
> > +		intel_dp->fallback_lane_count = 0;
> 
> Hm, I thought we agreed on irc to just track the max link rate/lane count
> at all times, instead of fallback values that sometimes are valid and
> sometimes reset to 0.
> 
> Also, resetting to 0 here is wrong, since this is not the long-pulse hpd
> handler. That probably also explains why you need the hack below, but not
> sure.
> 
> >  
> >  		if (intel_dp->is_mst) {
> >  			DRM_DEBUG_KMS("MST device may have disappeared %d vs %d\n",
> > @@ -4526,6 +4528,13 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
> >  	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
> >  		      connector->base.id, connector->name);
> >  
> > +	/* If this is a retry due to link training failure
> > +	 * then do no do a full detect
> > +	 */
> > +	if (status == connector_status_connected &&
> > +	    intel_dp->fallback_lane_count)
> > +		return status;
> 
> That sounds very wrong. Why do we need it?
> 
> > +
> >  	/* If full detect is not performed yet, do a full detect */
> >  	if (!intel_dp->detect_done)
> >  		status = intel_dp_long_pulse(intel_dp->attached_connector);
> > @@ -5690,6 +5699,37 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
> >  	return false;
> >  }
> >  
> > +static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
> > +{
> > +	struct intel_connector *intel_connector;
> > +	struct drm_connector *connector;
> > +	struct drm_display_mode *mode;
> > +	bool verbose_prune = true;
> > +
> > +	intel_connector = container_of(work, typeof(*intel_connector),
> > +				       modeset_retry_work);
> > +	connector = &intel_connector->base;
> > +	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
> > +		      connector->name);
> > +
> > +	/* Grab the locks before changing connector property*/
> > +	mutex_lock(&connector->dev->mode_config.mutex);
> > +	/* Set connector link status to BAD and send a Uevent to notify
> > +	 * userspace to do a modeset.
> > +	 */
> > +	drm_mode_connector_set_link_status_property(connector,
> > +						    DRM_MODE_LINK_STATUS_BAD);
> > +	list_for_each_entry(mode, &connector->modes, head) {
> > +		mode->status = intel_dp_mode_valid(connector,
> > +						   mode);
> > +	}
> > +	drm_mode_prune_invalid(connector->dev, &connector->modes,
> > +			       verbose_prune);
> 
> This call to drm_mode_prune_invalid is probably just to paper over a bug
> in SNA - SNA violates the hotplug handling uabi by not unconditionally
> reprobing. Inconsistently paper over that bug in the kernel is not good,
> userspace interfaces need to be well defined. Please remove this call and
> test with either UXA or -modesetting until SNA is fixed.

This is not required for link retraining in userspace, since userspace's
response to seeing the link-status == BAD property is to retrain the
current mode (and then it checks link-status again to see if the modeset
worked because returning an error from the modeset seems troublesome).
After that it reprobes. However, the kernel must still fail the modeset
following link-status = BAD if it decides that the mode is no longer
valid.
-Chris

-- 
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Re: [Intel-gfx] [PATCH 3/3] drm/i915: Implement Link Rate fallback on Link training failure

[Chris Wilson]

On Wed, Nov 30, 2016 at 09:36:33AM +0100, Daniel Vetter wrote:
> On Tue, Nov 29, 2016 at 11:30:33PM -0800, Manasi Navare wrote:
> > +static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
> > +{
> > +	struct intel_connector *intel_connector;
> > +	struct drm_connector *connector;
> > +	struct drm_display_mode *mode;
> > +	bool verbose_prune = true;
> > +
> > +	intel_connector = container_of(work, typeof(*intel_connector),
> > +				       modeset_retry_work);
> > +	connector = &intel_connector->base;
> > +	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
> > +		      connector->name);
> > +
> > +	/* Grab the locks before changing connector property*/
> > +	mutex_lock(&connector->dev->mode_config.mutex);
> > +	/* Set connector link status to BAD and send a Uevent to notify
> > +	 * userspace to do a modeset.
> > +	 */
> > +	drm_mode_connector_set_link_status_property(connector,
> > +						    DRM_MODE_LINK_STATUS_BAD);
> > +	list_for_each_entry(mode, &connector->modes, head) {
> > +		mode->status = intel_dp_mode_valid(connector,
> > +						   mode);
> > +	}
> > +	drm_mode_prune_invalid(connector->dev, &connector->modes,
> > +			       verbose_prune);
> 
> This call to drm_mode_prune_invalid is probably just to paper over a bug
> in SNA - SNA violates the hotplug handling uabi by not unconditionally
> reprobing. Inconsistently paper over that bug in the kernel is not good,
> userspace interfaces need to be well defined. Please remove this call and
> test with either UXA or -modesetting until SNA is fixed.

Then you should also categorically state that (once again) misusing the
HOTPLUG uevent for notification of a property update is wrong.
-Chris

-- 
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Re: [PATCH 3/3] drm/i915: Implement Link Rate fallback on Link training failure

[Ville Syrjälä]

On Wed, Nov 30, 2016 at 09:36:33AM +0100, Daniel Vetter wrote:
> On Tue, Nov 29, 2016 at 11:30:33PM -0800, Manasi Navare wrote:
> > If link training at a link rate optimal for a particular
> > mode fails during modeset's atomic commit phase, then we
> > let the modeset complete and then retry. We save the link rate
> > value at which link training failed, update the link status property
> > to "BAD" and use a lower link rate to prune the modes. It will redo
> > the modeset on the current mode at lower link rate or if the current
> > mode gets pruned due to lower link constraints then, it will send a
> > hotplug uevent for userspace to handle it.
> > 
> > This is also required to pass DP CTS tests 4.3.1.3, 4.3.1.4,
> > 4.3.1.6.
> > 
> > v9:
> > * Use the trimmed max values of link rate/lane count based on
> > link train fallback (Daniel Vetter)
> > v8:
> > * Set link_status to BAD first and then call mode_valid (Jani Nikula)
> > v7:
> > Remove the redundant variable in previous patch itself
> > v6:
> > * Obtain link rate index from fallback_link_rate using
> > the helper intel_dp_link_rate_index (Jani Nikula)
> > * Include fallback within intel_dp_start_link_train (Jani Nikula)
> > v5:
> > * Move set link status to drm core (Daniel Vetter, Jani Nikula)
> > v4:
> > * Add fallback support for non DDI platforms too
> > * Set connector->link status inside set_link_status function
> > (Jani Nikula)
> > v3:
> > * Set link status property to BAd unconditionally (Jani Nikula)
> > * Dont use two separate variables link_train_failed and link_status
> > to indicate same thing (Jani Nikula)
> > v2:
> > * Squashed a few patches (Jani Nikula)
> > 
> > Acked-by: Tony Cheng <tony.cheng@amd.com>
> > Acked-by: Harry Wentland <Harry.wentland@amd.com>
> > Cc: Jani Nikula <jani.nikula@linux.intel.com>
> > Cc: Daniel Vetter <daniel.vetter@intel.com>
> > Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> > Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_dp.c               | 44 +++++++++++++++++++++++++++
> >  drivers/gpu/drm/i915/intel_dp_link_training.c | 25 +++++++++++++--
> >  drivers/gpu/drm/i915/intel_drv.h              |  3 ++
> >  3 files changed, 70 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > index bc1268c..a50b6cd 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -4435,6 +4435,8 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
> >  		intel_dp->compliance_test_active = 0;
> >  		intel_dp->compliance_test_type = 0;
> >  		intel_dp->compliance_test_data = 0;
> > +		intel_dp->fallback_link_rate = 0;
> > +		intel_dp->fallback_lane_count = 0;
> 
> Hm, I thought we agreed on irc to just track the max link rate/lane count
> at all times, instead of fallback values that sometimes are valid and
> sometimes reset to 0.
> 
> Also, resetting to 0 here is wrong, since this is not the long-pulse hpd
> handler. That probably also explains why you need the hack below, but not
> sure.
> 
> >  
> >  		if (intel_dp->is_mst) {
> >  			DRM_DEBUG_KMS("MST device may have disappeared %d vs %d\n",
> > @@ -4526,6 +4528,13 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
> >  	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
> >  		      connector->base.id, connector->name);
> >  
> > +	/* If this is a retry due to link training failure
> > +	 * then do no do a full detect
> > +	 */
> > +	if (status == connector_status_connected &&
> > +	    intel_dp->fallback_lane_count)
> > +		return status;
> 
> That sounds very wrong. Why do we need it?
> 
> > +
> >  	/* If full detect is not performed yet, do a full detect */
> >  	if (!intel_dp->detect_done)
> >  		status = intel_dp_long_pulse(intel_dp->attached_connector);
> > @@ -5690,6 +5699,37 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
> >  	return false;
> >  }
> >  
> > +static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
> > +{
> > +	struct intel_connector *intel_connector;
> > +	struct drm_connector *connector;
> > +	struct drm_display_mode *mode;
> > +	bool verbose_prune = true;
> > +
> > +	intel_connector = container_of(work, typeof(*intel_connector),
> > +				       modeset_retry_work);
> > +	connector = &intel_connector->base;
> > +	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
> > +		      connector->name);
> > +
> > +	/* Grab the locks before changing connector property*/
> > +	mutex_lock(&connector->dev->mode_config.mutex);
> > +	/* Set connector link status to BAD and send a Uevent to notify
> > +	 * userspace to do a modeset.
> > +	 */
> > +	drm_mode_connector_set_link_status_property(connector,
> > +						    DRM_MODE_LINK_STATUS_BAD);
> > +	list_for_each_entry(mode, &connector->modes, head) {
> > +		mode->status = intel_dp_mode_valid(connector,
> > +						   mode);
> > +	}
> > +	drm_mode_prune_invalid(connector->dev, &connector->modes,
> > +			       verbose_prune);
> 
> This call to drm_mode_prune_invalid is probably just to paper over a bug
> in SNA - SNA violates the hotplug handling uabi by not unconditionally
> reprobing. Inconsistently paper over that bug in the kernel is not good,

I would categorize pruning here as "avoid pointless work later". Of
course with the current uabi that might not happen anyway. Would be
nice if it eventually did however.

-- 
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Intel OTC
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Re: [PATCH 1/3] drm: Add a new connector atomic property for link status

[Manasi Navare]

Sean, could you please review this patch, I have tried to address
all the comments from you.

Regards
Manasi

On Tue, Nov 29, 2016 at 11:30:31PM -0800, Manasi Navare wrote:
> At the time userspace does setcrtc, we've already promised the mode
> would work. The promise is based on the theoretical capabilities of
> the link, but it's possible we can't reach this in practice. The DP
> spec describes how the link should be reduced, but we can't reduce
> the link below the requirements of the mode. Black screen follows.
> 
> One idea would be to have setcrtc return a failure. However, it
> already should not fail as the atomic checks have passed. It would
> also conflict with the idea of making setcrtc asynchronous in the
> future, returning before the actual mode setting and link training.
> 
> Another idea is to train the link "upfront" at hotplug time, before
> pruning the mode list, so that we can do the pruning based on
> practical not theoretical capabilities. However, the changes for link
> training are pretty drastic, all for the sake of error handling and
> DP compliance, when the most common happy day scenario is the current
> approach of link training at mode setting time, using the optimal
> parameters for the mode. It is also not certain all hardware could do
> this without the pipe on; not even all our hardware can do this. Some
> of this can be solved, but not trivially.
> 
> Both of the above ideas also fail to address link degradation *during*
> operation.
> 
> The solution is to add a new "link-status" connector property in order
> to address link training failure in a way that:
> a) changes the current happy day scenario as little as possible, to
> avoid regressions, b) can be implemented the same way by all drm
> drivers, c) is still opt-in for the drivers and userspace, and opting
> out doesn't regress the user experience, d) doesn't prevent drivers
> from implementing better or alternate approaches, possibly without
> userspace involvement. And, of course, handles all the issues presented.
> In the usual happy day scenario, this is always "good". If something
> fails during or after a mode set, the kernel driver can set the link
> status to "bad" and issue a hotplug uevent for userspace to have it
> re-check the valid modes through GET_CONNECTOR IOCTL, and try modeset
> again. If the theoretical capabilities of the link can't be reached,
> the mode list is trimmed based on that.
> 
> v4:
> * Add comments in kernel-doc format (Daniel Vetter)
> * Update the kernel-doc for link-status (Sean Paul)
> v3:
> * Fixed a build error (Jani Saarinen)
> v2:
> * Removed connector->link_status (Daniel Vetter)
> * Set connector->state->link_status in drm_mode_connector_set_link_status_property
> (Daniel Vetter)
> * Set the connector_changed flag to true if connector->state->link_status changed.
> * Reset link_status to GOOD in update_output_state (Daniel Vetter)
> * Never allow userspace to set link status from Good To Bad (Daniel Vetter)
> 
> Acked-by: Tony Cheng <tony.cheng@amd.com>
> Acked-by: Harry Wentland <harry.wentland@amd.com>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Sean Paul <seanpaul@chromium.org>
> Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> ---
>  drivers/gpu/drm/drm_atomic.c        | 10 +++++++
>  drivers/gpu/drm/drm_atomic_helper.c |  8 ++++++
>  drivers/gpu/drm/drm_connector.c     | 54 ++++++++++++++++++++++++++++++++++++-
>  include/drm/drm_connector.h         | 19 +++++++++++++
>  include/drm/drm_mode_config.h       |  5 ++++
>  include/uapi/drm/drm_mode.h         |  4 +++
>  6 files changed, 99 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index 89737e4..990f013 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -1087,6 +1087,14 @@ int drm_atomic_connector_set_property(struct drm_connector *connector,
>  		 * now?) atomic writes to DPMS property:
>  		 */
>  		return -EINVAL;
> +	} else if (property == config->link_status_property) {
> +		/* Never downgrade from GOOD to BAD on userspace's request here,
> +		 * only hw issues can do that.
> +		 */
> +		if (state->link_status == DRM_LINK_STATUS_GOOD)
> +			return 0;
> +		state->link_status = val;
> +		return 0;
>  	} else if (connector->funcs->atomic_set_property) {
>  		return connector->funcs->atomic_set_property(connector,
>  				state, property, val);
> @@ -1135,6 +1143,8 @@ static void drm_atomic_connector_print_state(struct drm_printer *p,
>  		*val = (state->crtc) ? state->crtc->base.id : 0;
>  	} else if (property == config->dpms_property) {
>  		*val = connector->dpms;
> +	} else if (property == config->link_status_property) {
> +		*val = state->link_status;
>  	} else if (connector->funcs->atomic_get_property) {
>  		return connector->funcs->atomic_get_property(connector,
>  				state, property, val);
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 494680c..962ed66 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -519,6 +519,13 @@ static int handle_conflicting_encoders(struct drm_atomic_state *state,
>  					       connector_state);
>  		if (ret)
>  			return ret;
> +		if (connector->state->crtc) {
> +			crtc_state = drm_atomic_get_existing_crtc_state(state,
> +									connector->state->crtc);
> +			if (connector->state->link_status !=
> +			    connector_state->link_status)
> +				crtc_state->connectors_changed = true;
> +		}
>  	}
>  
>  	/*
> @@ -2258,6 +2265,7 @@ static int update_output_state(struct drm_atomic_state *state,
>  								NULL);
>  			if (ret)
>  				return ret;
> +			conn_state->link_status = DRM_LINK_STATUS_GOOD;
>  		}
>  	}
>  
> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> index 5a45262..8902367 100644
> --- a/drivers/gpu/drm/drm_connector.c
> +++ b/drivers/gpu/drm/drm_connector.c
> @@ -243,6 +243,10 @@ int drm_connector_init(struct drm_device *dev,
>  	drm_object_attach_property(&connector->base,
>  				      config->dpms_property, 0);
>  
> +	drm_object_attach_property(&connector->base,
> +				   config->link_status_property,
> +				   0);
> +
>  	if (drm_core_check_feature(dev, DRIVER_ATOMIC)) {
>  		drm_object_attach_property(&connector->base, config->prop_crtc_id, 0);
>  	}
> @@ -506,6 +510,12 @@ const char *drm_get_subpixel_order_name(enum subpixel_order order)
>  };
>  DRM_ENUM_NAME_FN(drm_get_dpms_name, drm_dpms_enum_list)
>  
> +static const struct drm_prop_enum_list drm_link_status_enum_list[] = {
> +	{ DRM_MODE_LINK_STATUS_GOOD, "Good" },
> +	{ DRM_MODE_LINK_STATUS_BAD, "Bad" },
> +};
> +DRM_ENUM_NAME_FN(drm_get_link_status_name, drm_link_status_enum_list)
> +
>  /**
>   * drm_display_info_set_bus_formats - set the supported bus formats
>   * @info: display info to store bus formats in
> @@ -625,7 +635,11 @@ int drm_display_info_set_bus_formats(struct drm_display_info *info,
>   * 	tiling and virtualize both &drm_crtc and &drm_plane if needed. Drivers
>   * 	should update this value using drm_mode_connector_set_tile_property().
>   * 	Userspace cannot change this property.
> - *
> + * link-status:
> + *      Connector link-status property to indicate the status of link. The default
> + *      value of link-status is "GOOD". If something fails during or after modeset,
> + *      the kernel driver may set this to "BAD" and issue a hotplug uevent. Drivers
> + *      should update this value using drm_mode_connector_set_link_status_property().
>   * Connectors also have one standardized atomic property:
>   *
>   * CRTC_ID:
> @@ -666,6 +680,13 @@ int drm_connector_create_standard_properties(struct drm_device *dev)
>  		return -ENOMEM;
>  	dev->mode_config.tile_property = prop;
>  
> +	prop = drm_property_create_enum(dev, 0, "link-status",
> +					drm_link_status_enum_list,
> +					ARRAY_SIZE(drm_link_status_enum_list));
> +	if (!prop)
> +		return -ENOMEM;
> +	dev->mode_config.link_status_property = prop;
> +
>  	return 0;
>  }
>  
> @@ -995,6 +1016,37 @@ int drm_mode_connector_update_edid_property(struct drm_connector *connector,
>  }
>  EXPORT_SYMBOL(drm_mode_connector_update_edid_property);
>  
> +/**
> + * drm_mode_connector_set_link_status_property - Set link status property of a connector
> + * @connector: drm connector
> + * @link_status: new value of link status property (0: Good, 1: Bad)
> + *
> + * In usual working scenario, this link status property will always be set to
> + * "GOOD". If something fails during or after a mode set, the kernel driver
> + * may set this link status property to "BAD". The caller then needs to send a
> + * hotplug uevent for userspace to re-check the valid modes through
> + * GET_CONNECTOR_IOCTL and retry modeset.
> + *
> + * Note: Drivers cannot rely on userspace to support this property and
> + * issue a modeset. As such, they may choose to handle issues (like
> + * re-training a link) without userspace's intervention.
> + *
> + * The reason for adding this property is to handle link training failures, but
> + * it is not limited to DP or link training. For example, if we implement
> + * asynchronous setcrtc, this property can be used to report any failures in that.
> + */
> +void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
> +						 uint64_t link_status)
> +{
> +	struct drm_device *dev = connector->dev;
> +
> +	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
> +	connector->state->link_status = link_status;
> +	drm_modeset_unlock(&dev->mode_config.connection_mutex);
> +
> +}
> +EXPORT_SYMBOL(drm_mode_connector_set_link_status_property);
> +
>  int drm_mode_connector_set_obj_prop(struct drm_mode_object *obj,
>  				    struct drm_property *property,
>  				    uint64_t value)
> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> index 34f9741..53c5f70 100644
> --- a/include/drm/drm_connector.h
> +++ b/include/drm/drm_connector.h
> @@ -90,6 +90,17 @@ enum subpixel_order {
>  };
>  
>  /**
> + * enum drm_link_status - connector's link_status property value
> + *
> + * This enum is used as the connector's link status property value.
> + * It is set to the values defined in uapi.
> + */
> +enum drm_link_status {
> +	DRM_LINK_STATUS_GOOD = DRM_MODE_LINK_STATUS_GOOD,
> +	DRM_LINK_STATUS_BAD = DRM_MODE_LINK_STATUS_BAD,
> +};
> +
> +/**
>   * struct drm_display_info - runtime data about the connected sink
>   *
>   * Describes a given display (e.g. CRT or flat panel) and its limitations. For
> @@ -213,6 +224,12 @@ struct drm_connector_state {
>  
>  	struct drm_encoder *best_encoder;
>  
> +	/**
> +	 * @link_status: Connector link_status to keep track of whether link is
> +	 * GOOD or BAD to notify userspace if retraining is necessary.
> +	 */
> +	enum drm_link_status link_status;
> +
>  	struct drm_atomic_state *state;
>  };
>  
> @@ -773,6 +790,8 @@ int drm_mode_connector_set_path_property(struct drm_connector *connector,
>  int drm_mode_connector_set_tile_property(struct drm_connector *connector);
>  int drm_mode_connector_update_edid_property(struct drm_connector *connector,
>  					    const struct edid *edid);
> +void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
> +						 uint64_t link_status);
>  
>  /**
>   * struct drm_tile_group - Tile group metadata
> diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
> index bf9991b..86faee4 100644
> --- a/include/drm/drm_mode_config.h
> +++ b/include/drm/drm_mode_config.h
> @@ -431,6 +431,11 @@ struct drm_mode_config {
>  	 */
>  	struct drm_property *tile_property;
>  	/**
> +	 * @link_status_property: Default connector property for link status
> +	 * of a connector
> +	 */
> +	struct drm_property *link_status_property;
> +	/**
>  	 * @plane_type_property: Default plane property to differentiate
>  	 * CURSOR, PRIMARY and OVERLAY legacy uses of planes.
>  	 */
> diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
> index 728790b..309c478 100644
> --- a/include/uapi/drm/drm_mode.h
> +++ b/include/uapi/drm/drm_mode.h
> @@ -123,6 +123,10 @@
>  #define DRM_MODE_DIRTY_ON       1
>  #define DRM_MODE_DIRTY_ANNOTATE 2
>  
> +/* Link Status options */
> +#define DRM_MODE_LINK_STATUS_GOOD	0
> +#define DRM_MODE_LINK_STATUS_BAD	1
> +
>  struct drm_mode_modeinfo {
>  	__u32 clock;
>  	__u16 hdisplay;
> -- 
> 1.9.1
> 
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Re: [PATCH 1/3] drm: Add a new connector atomic property for link status

[Sean Paul]

On Thu, Dec 1, 2016 at 1:58 PM, Manasi Navare <manasi.d.navare@intel.com> wrote:
> Sean, could you please review this patch, I have tried to address
> all the comments from you.
>

Comments look good to me.

Reviewed-by: Sean Paul <seanpaul@chromium.org>

Sean

> Regards
> Manasi
>
> On Tue, Nov 29, 2016 at 11:30:31PM -0800, Manasi Navare wrote:
>> At the time userspace does setcrtc, we've already promised the mode
>> would work. The promise is based on the theoretical capabilities of
>> the link, but it's possible we can't reach this in practice. The DP
>> spec describes how the link should be reduced, but we can't reduce
>> the link below the requirements of the mode. Black screen follows.
>>
>> One idea would be to have setcrtc return a failure. However, it
>> already should not fail as the atomic checks have passed. It would
>> also conflict with the idea of making setcrtc asynchronous in the
>> future, returning before the actual mode setting and link training.
>>
>> Another idea is to train the link "upfront" at hotplug time, before
>> pruning the mode list, so that we can do the pruning based on
>> practical not theoretical capabilities. However, the changes for link
>> training are pretty drastic, all for the sake of error handling and
>> DP compliance, when the most common happy day scenario is the current
>> approach of link training at mode setting time, using the optimal
>> parameters for the mode. It is also not certain all hardware could do
>> this without the pipe on; not even all our hardware can do this. Some
>> of this can be solved, but not trivially.
>>
>> Both of the above ideas also fail to address link degradation *during*
>> operation.
>>
>> The solution is to add a new "link-status" connector property in order
>> to address link training failure in a way that:
>> a) changes the current happy day scenario as little as possible, to
>> avoid regressions, b) can be implemented the same way by all drm
>> drivers, c) is still opt-in for the drivers and userspace, and opting
>> out doesn't regress the user experience, d) doesn't prevent drivers
>> from implementing better or alternate approaches, possibly without
>> userspace involvement. And, of course, handles all the issues presented.
>> In the usual happy day scenario, this is always "good". If something
>> fails during or after a mode set, the kernel driver can set the link
>> status to "bad" and issue a hotplug uevent for userspace to have it
>> re-check the valid modes through GET_CONNECTOR IOCTL, and try modeset
>> again. If the theoretical capabilities of the link can't be reached,
>> the mode list is trimmed based on that.
>>
>> v4:
>> * Add comments in kernel-doc format (Daniel Vetter)
>> * Update the kernel-doc for link-status (Sean Paul)
>> v3:
>> * Fixed a build error (Jani Saarinen)
>> v2:
>> * Removed connector->link_status (Daniel Vetter)
>> * Set connector->state->link_status in drm_mode_connector_set_link_status_property
>> (Daniel Vetter)
>> * Set the connector_changed flag to true if connector->state->link_status changed.
>> * Reset link_status to GOOD in update_output_state (Daniel Vetter)
>> * Never allow userspace to set link status from Good To Bad (Daniel Vetter)
>>
>> Acked-by: Tony Cheng <tony.cheng@amd.com>
>> Acked-by: Harry Wentland <harry.wentland@amd.com>
>> Cc: Jani Nikula <jani.nikula@linux.intel.com>
>> Cc: Daniel Vetter <daniel.vetter@intel.com>
>> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
>> Cc: Chris Wilson <chris@chris-wilson.co.uk>
>> Cc: Sean Paul <seanpaul@chromium.org>
>> Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
>> ---
>>  drivers/gpu/drm/drm_atomic.c        | 10 +++++++
>>  drivers/gpu/drm/drm_atomic_helper.c |  8 ++++++
>>  drivers/gpu/drm/drm_connector.c     | 54 ++++++++++++++++++++++++++++++++++++-
>>  include/drm/drm_connector.h         | 19 +++++++++++++
>>  include/drm/drm_mode_config.h       |  5 ++++
>>  include/uapi/drm/drm_mode.h         |  4 +++
>>  6 files changed, 99 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
>> index 89737e4..990f013 100644
>> --- a/drivers/gpu/drm/drm_atomic.c
>> +++ b/drivers/gpu/drm/drm_atomic.c
>> @@ -1087,6 +1087,14 @@ int drm_atomic_connector_set_property(struct drm_connector *connector,
>>                * now?) atomic writes to DPMS property:
>>                */
>>               return -EINVAL;
>> +     } else if (property == config->link_status_property) {
>> +             /* Never downgrade from GOOD to BAD on userspace's request here,
>> +              * only hw issues can do that.
>> +              */
>> +             if (state->link_status == DRM_LINK_STATUS_GOOD)
>> +                     return 0;
>> +             state->link_status = val;
>> +             return 0;
>>       } else if (connector->funcs->atomic_set_property) {
>>               return connector->funcs->atomic_set_property(connector,
>>                               state, property, val);
>> @@ -1135,6 +1143,8 @@ static void drm_atomic_connector_print_state(struct drm_printer *p,
>>               *val = (state->crtc) ? state->crtc->base.id : 0;
>>       } else if (property == config->dpms_property) {
>>               *val = connector->dpms;
>> +     } else if (property == config->link_status_property) {
>> +             *val = state->link_status;
>>       } else if (connector->funcs->atomic_get_property) {
>>               return connector->funcs->atomic_get_property(connector,
>>                               state, property, val);
>> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
>> index 494680c..962ed66 100644
>> --- a/drivers/gpu/drm/drm_atomic_helper.c
>> +++ b/drivers/gpu/drm/drm_atomic_helper.c
>> @@ -519,6 +519,13 @@ static int handle_conflicting_encoders(struct drm_atomic_state *state,
>>                                              connector_state);
>>               if (ret)
>>                       return ret;
>> +             if (connector->state->crtc) {
>> +                     crtc_state = drm_atomic_get_existing_crtc_state(state,
>> +                                                                     connector->state->crtc);
>> +                     if (connector->state->link_status !=
>> +                         connector_state->link_status)
>> +                             crtc_state->connectors_changed = true;
>> +             }
>>       }
>>
>>       /*
>> @@ -2258,6 +2265,7 @@ static int update_output_state(struct drm_atomic_state *state,
>>                                                               NULL);
>>                       if (ret)
>>                               return ret;
>> +                     conn_state->link_status = DRM_LINK_STATUS_GOOD;
>>               }
>>       }
>>
>> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
>> index 5a45262..8902367 100644
>> --- a/drivers/gpu/drm/drm_connector.c
>> +++ b/drivers/gpu/drm/drm_connector.c
>> @@ -243,6 +243,10 @@ int drm_connector_init(struct drm_device *dev,
>>       drm_object_attach_property(&connector->base,
>>                                     config->dpms_property, 0);
>>
>> +     drm_object_attach_property(&connector->base,
>> +                                config->link_status_property,
>> +                                0);
>> +
>>       if (drm_core_check_feature(dev, DRIVER_ATOMIC)) {
>>               drm_object_attach_property(&connector->base, config->prop_crtc_id, 0);
>>       }
>> @@ -506,6 +510,12 @@ const char *drm_get_subpixel_order_name(enum subpixel_order order)
>>  };
>>  DRM_ENUM_NAME_FN(drm_get_dpms_name, drm_dpms_enum_list)
>>
>> +static const struct drm_prop_enum_list drm_link_status_enum_list[] = {
>> +     { DRM_MODE_LINK_STATUS_GOOD, "Good" },
>> +     { DRM_MODE_LINK_STATUS_BAD, "Bad" },
>> +};
>> +DRM_ENUM_NAME_FN(drm_get_link_status_name, drm_link_status_enum_list)
>> +
>>  /**
>>   * drm_display_info_set_bus_formats - set the supported bus formats
>>   * @info: display info to store bus formats in
>> @@ -625,7 +635,11 @@ int drm_display_info_set_bus_formats(struct drm_display_info *info,
>>   *   tiling and virtualize both &drm_crtc and &drm_plane if needed. Drivers
>>   *   should update this value using drm_mode_connector_set_tile_property().
>>   *   Userspace cannot change this property.
>> - *
>> + * link-status:
>> + *      Connector link-status property to indicate the status of link. The default
>> + *      value of link-status is "GOOD". If something fails during or after modeset,
>> + *      the kernel driver may set this to "BAD" and issue a hotplug uevent. Drivers
>> + *      should update this value using drm_mode_connector_set_link_status_property().
>>   * Connectors also have one standardized atomic property:
>>   *
>>   * CRTC_ID:
>> @@ -666,6 +680,13 @@ int drm_connector_create_standard_properties(struct drm_device *dev)
>>               return -ENOMEM;
>>       dev->mode_config.tile_property = prop;
>>
>> +     prop = drm_property_create_enum(dev, 0, "link-status",
>> +                                     drm_link_status_enum_list,
>> +                                     ARRAY_SIZE(drm_link_status_enum_list));
>> +     if (!prop)
>> +             return -ENOMEM;
>> +     dev->mode_config.link_status_property = prop;
>> +
>>       return 0;
>>  }
>>
>> @@ -995,6 +1016,37 @@ int drm_mode_connector_update_edid_property(struct drm_connector *connector,
>>  }
>>  EXPORT_SYMBOL(drm_mode_connector_update_edid_property);
>>
>> +/**
>> + * drm_mode_connector_set_link_status_property - Set link status property of a connector
>> + * @connector: drm connector
>> + * @link_status: new value of link status property (0: Good, 1: Bad)
>> + *
>> + * In usual working scenario, this link status property will always be set to
>> + * "GOOD". If something fails during or after a mode set, the kernel driver
>> + * may set this link status property to "BAD". The caller then needs to send a
>> + * hotplug uevent for userspace to re-check the valid modes through
>> + * GET_CONNECTOR_IOCTL and retry modeset.
>> + *
>> + * Note: Drivers cannot rely on userspace to support this property and
>> + * issue a modeset. As such, they may choose to handle issues (like
>> + * re-training a link) without userspace's intervention.
>> + *
>> + * The reason for adding this property is to handle link training failures, but
>> + * it is not limited to DP or link training. For example, if we implement
>> + * asynchronous setcrtc, this property can be used to report any failures in that.
>> + */
>> +void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
>> +                                              uint64_t link_status)
>> +{
>> +     struct drm_device *dev = connector->dev;
>> +
>> +     drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
>> +     connector->state->link_status = link_status;
>> +     drm_modeset_unlock(&dev->mode_config.connection_mutex);
>> +
>> +}
>> +EXPORT_SYMBOL(drm_mode_connector_set_link_status_property);
>> +
>>  int drm_mode_connector_set_obj_prop(struct drm_mode_object *obj,
>>                                   struct drm_property *property,
>>                                   uint64_t value)
>> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
>> index 34f9741..53c5f70 100644
>> --- a/include/drm/drm_connector.h
>> +++ b/include/drm/drm_connector.h
>> @@ -90,6 +90,17 @@ enum subpixel_order {
>>  };
>>
>>  /**
>> + * enum drm_link_status - connector's link_status property value
>> + *
>> + * This enum is used as the connector's link status property value.
>> + * It is set to the values defined in uapi.
>> + */
>> +enum drm_link_status {
>> +     DRM_LINK_STATUS_GOOD = DRM_MODE_LINK_STATUS_GOOD,
>> +     DRM_LINK_STATUS_BAD = DRM_MODE_LINK_STATUS_BAD,
>> +};
>> +
>> +/**
>>   * struct drm_display_info - runtime data about the connected sink
>>   *
>>   * Describes a given display (e.g. CRT or flat panel) and its limitations. For
>> @@ -213,6 +224,12 @@ struct drm_connector_state {
>>
>>       struct drm_encoder *best_encoder;
>>
>> +     /**
>> +      * @link_status: Connector link_status to keep track of whether link is
>> +      * GOOD or BAD to notify userspace if retraining is necessary.
>> +      */
>> +     enum drm_link_status link_status;
>> +
>>       struct drm_atomic_state *state;
>>  };
>>
>> @@ -773,6 +790,8 @@ int drm_mode_connector_set_path_property(struct drm_connector *connector,
>>  int drm_mode_connector_set_tile_property(struct drm_connector *connector);
>>  int drm_mode_connector_update_edid_property(struct drm_connector *connector,
>>                                           const struct edid *edid);
>> +void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
>> +                                              uint64_t link_status);
>>
>>  /**
>>   * struct drm_tile_group - Tile group metadata
>> diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
>> index bf9991b..86faee4 100644
>> --- a/include/drm/drm_mode_config.h
>> +++ b/include/drm/drm_mode_config.h
>> @@ -431,6 +431,11 @@ struct drm_mode_config {
>>        */
>>       struct drm_property *tile_property;
>>       /**
>> +      * @link_status_property: Default connector property for link status
>> +      * of a connector
>> +      */
>> +     struct drm_property *link_status_property;
>> +     /**
>>        * @plane_type_property: Default plane property to differentiate
>>        * CURSOR, PRIMARY and OVERLAY legacy uses of planes.
>>        */
>> diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
>> index 728790b..309c478 100644
>> --- a/include/uapi/drm/drm_mode.h
>> +++ b/include/uapi/drm/drm_mode.h
>> @@ -123,6 +123,10 @@
>>  #define DRM_MODE_DIRTY_ON       1
>>  #define DRM_MODE_DIRTY_ANNOTATE 2
>>
>> +/* Link Status options */
>> +#define DRM_MODE_LINK_STATUS_GOOD    0
>> +#define DRM_MODE_LINK_STATUS_BAD     1
>> +
>>  struct drm_mode_modeinfo {
>>       __u32 clock;
>>       __u16 hdisplay;
>> --
>> 1.9.1
>>
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Re: [PATCH 1/3] drm: Add a new connector atomic property for link status

[Daniel Vetter]

On Tue, Nov 29, 2016 at 11:30:31PM -0800, Manasi Navare wrote:
> At the time userspace does setcrtc, we've already promised the mode
> would work. The promise is based on the theoretical capabilities of
> the link, but it's possible we can't reach this in practice. The DP
> spec describes how the link should be reduced, but we can't reduce
> the link below the requirements of the mode. Black screen follows.
> 
> One idea would be to have setcrtc return a failure. However, it
> already should not fail as the atomic checks have passed. It would
> also conflict with the idea of making setcrtc asynchronous in the
> future, returning before the actual mode setting and link training.
> 
> Another idea is to train the link "upfront" at hotplug time, before
> pruning the mode list, so that we can do the pruning based on
> practical not theoretical capabilities. However, the changes for link
> training are pretty drastic, all for the sake of error handling and
> DP compliance, when the most common happy day scenario is the current
> approach of link training at mode setting time, using the optimal
> parameters for the mode. It is also not certain all hardware could do
> this without the pipe on; not even all our hardware can do this. Some
> of this can be solved, but not trivially.
> 
> Both of the above ideas also fail to address link degradation *during*
> operation.
> 
> The solution is to add a new "link-status" connector property in order
> to address link training failure in a way that:
> a) changes the current happy day scenario as little as possible, to
> avoid regressions, b) can be implemented the same way by all drm
> drivers, c) is still opt-in for the drivers and userspace, and opting
> out doesn't regress the user experience, d) doesn't prevent drivers
> from implementing better or alternate approaches, possibly without
> userspace involvement. And, of course, handles all the issues presented.
> In the usual happy day scenario, this is always "good". If something
> fails during or after a mode set, the kernel driver can set the link
> status to "bad" and issue a hotplug uevent for userspace to have it
> re-check the valid modes through GET_CONNECTOR IOCTL, and try modeset
> again. If the theoretical capabilities of the link can't be reached,
> the mode list is trimmed based on that.
> 
> v4:
> * Add comments in kernel-doc format (Daniel Vetter)
> * Update the kernel-doc for link-status (Sean Paul)
> v3:
> * Fixed a build error (Jani Saarinen)
> v2:
> * Removed connector->link_status (Daniel Vetter)
> * Set connector->state->link_status in drm_mode_connector_set_link_status_property
> (Daniel Vetter)
> * Set the connector_changed flag to true if connector->state->link_status changed.
> * Reset link_status to GOOD in update_output_state (Daniel Vetter)
> * Never allow userspace to set link status from Good To Bad (Daniel Vetter)
> 
> Acked-by: Tony Cheng <tony.cheng@amd.com>
> Acked-by: Harry Wentland <harry.wentland@amd.com>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Sean Paul <seanpaul@chromium.org>
> Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> ---
>  drivers/gpu/drm/drm_atomic.c        | 10 +++++++
>  drivers/gpu/drm/drm_atomic_helper.c |  8 ++++++
>  drivers/gpu/drm/drm_connector.c     | 54 ++++++++++++++++++++++++++++++++++++-
>  include/drm/drm_connector.h         | 19 +++++++++++++
>  include/drm/drm_mode_config.h       |  5 ++++
>  include/uapi/drm/drm_mode.h         |  4 +++
>  6 files changed, 99 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index 89737e4..990f013 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -1087,6 +1087,14 @@ int drm_atomic_connector_set_property(struct drm_connector *connector,
>  		 * now?) atomic writes to DPMS property:
>  		 */
>  		return -EINVAL;
> +	} else if (property == config->link_status_property) {
> +		/* Never downgrade from GOOD to BAD on userspace's request here,
> +		 * only hw issues can do that.
> +		 */
> +		if (state->link_status == DRM_LINK_STATUS_GOOD)
> +			return 0;
> +		state->link_status = val;
> +		return 0;
>  	} else if (connector->funcs->atomic_set_property) {
>  		return connector->funcs->atomic_set_property(connector,
>  				state, property, val);
> @@ -1135,6 +1143,8 @@ static void drm_atomic_connector_print_state(struct drm_printer *p,
>  		*val = (state->crtc) ? state->crtc->base.id : 0;
>  	} else if (property == config->dpms_property) {
>  		*val = connector->dpms;
> +	} else if (property == config->link_status_property) {
> +		*val = state->link_status;
>  	} else if (connector->funcs->atomic_get_property) {
>  		return connector->funcs->atomic_get_property(connector,
>  				state, property, val);
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 494680c..962ed66 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -519,6 +519,13 @@ static int handle_conflicting_encoders(struct drm_atomic_state *state,
>  					       connector_state);
>  		if (ret)
>  			return ret;
> +		if (connector->state->crtc) {
> +			crtc_state = drm_atomic_get_existing_crtc_state(state,
> +									connector->state->crtc);
> +			if (connector->state->link_status !=
> +			    connector_state->link_status)
> +				crtc_state->connectors_changed = true;
> +		}

See my previous review, this looks should imo be moved to a more obvious
place than hidden deep down in the callchain.

>  	}
>  
>  	/*
> @@ -2258,6 +2265,7 @@ static int update_output_state(struct drm_atomic_state *state,
>  								NULL);
>  			if (ret)
>  				return ret;
> +			conn_state->link_status = DRM_LINK_STATUS_GOOD;

Iirc in our discussion we said a small comment here would be good, like

			/* Make sure legacy setCrtc always re-trains. */

Might also be good to update the kernel-doc of
drm_atomic_helper_set_config(). Something like

 * NOTE: For backwards compatibility with old userspace this automatically
 * resets the "link-status" property to GOOD, to force any link
 * re-training. The SETCRTC ioctl does not define whether an update does
 * need a full modeset or just a plane update, hence we're allowed to do
 * that. See also drm_mode_connector_set_link_status_property().
 * 

>  		}
>  	}
>  
> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> index 5a45262..8902367 100644
> --- a/drivers/gpu/drm/drm_connector.c
> +++ b/drivers/gpu/drm/drm_connector.c
> @@ -243,6 +243,10 @@ int drm_connector_init(struct drm_device *dev,
>  	drm_object_attach_property(&connector->base,
>  				      config->dpms_property, 0);
>  
> +	drm_object_attach_property(&connector->base,
> +				   config->link_status_property,
> +				   0);
> +
>  	if (drm_core_check_feature(dev, DRIVER_ATOMIC)) {
>  		drm_object_attach_property(&connector->base, config->prop_crtc_id, 0);
>  	}
> @@ -506,6 +510,12 @@ const char *drm_get_subpixel_order_name(enum subpixel_order order)
>  };
>  DRM_ENUM_NAME_FN(drm_get_dpms_name, drm_dpms_enum_list)
>  
> +static const struct drm_prop_enum_list drm_link_status_enum_list[] = {
> +	{ DRM_MODE_LINK_STATUS_GOOD, "Good" },
> +	{ DRM_MODE_LINK_STATUS_BAD, "Bad" },
> +};
> +DRM_ENUM_NAME_FN(drm_get_link_status_name, drm_link_status_enum_list)
> +
>  /**
>   * drm_display_info_set_bus_formats - set the supported bus formats
>   * @info: display info to store bus formats in
> @@ -625,7 +635,11 @@ int drm_display_info_set_bus_formats(struct drm_display_info *info,
>   * 	tiling and virtualize both &drm_crtc and &drm_plane if needed. Drivers
>   * 	should update this value using drm_mode_connector_set_tile_property().
>   * 	Userspace cannot change this property.
> - *

One more from last round: Please leave this whitespace intact ...

> + * link-status:
> + *      Connector link-status property to indicate the status of link. The default
> + *      value of link-status is "GOOD". If something fails during or after modeset,
> + *      the kernel driver may set this to "BAD" and issue a hotplug uevent. Drivers
> + *      should update this value using drm_mode_connector_set_link_status_property().

... and add an empty line here.

>   * Connectors also have one standardized atomic property:
>   *
>   * CRTC_ID:
> @@ -666,6 +680,13 @@ int drm_connector_create_standard_properties(struct drm_device *dev)
>  		return -ENOMEM;
>  	dev->mode_config.tile_property = prop;
>  
> +	prop = drm_property_create_enum(dev, 0, "link-status",
> +					drm_link_status_enum_list,
> +					ARRAY_SIZE(drm_link_status_enum_list));
> +	if (!prop)
> +		return -ENOMEM;
> +	dev->mode_config.link_status_property = prop;
> +
>  	return 0;
>  }
>  
> @@ -995,6 +1016,37 @@ int drm_mode_connector_update_edid_property(struct drm_connector *connector,
>  }
>  EXPORT_SYMBOL(drm_mode_connector_update_edid_property);
>  
> +/**
> + * drm_mode_connector_set_link_status_property - Set link status property of a connector
> + * @connector: drm connector
> + * @link_status: new value of link status property (0: Good, 1: Bad)
> + *
> + * In usual working scenario, this link status property will always be set to
> + * "GOOD". If something fails during or after a mode set, the kernel driver
> + * may set this link status property to "BAD". The caller then needs to send a
> + * hotplug uevent for userspace to re-check the valid modes through
> + * GET_CONNECTOR_IOCTL and retry modeset.
> + *
> + * Note: Drivers cannot rely on userspace to support this property and
> + * issue a modeset. As such, they may choose to handle issues (like
> + * re-training a link) without userspace's intervention.
> + *
> + * The reason for adding this property is to handle link training failures, but
> + * it is not limited to DP or link training. For example, if we implement
> + * asynchronous setcrtc, this property can be used to report any failures in that.
> + */
> +void drm_mode_connector_set_link_status_property(struct drm_connector *connector,

Hm, tiny new bikeshed: I'd drop the _property postfix here. The function
name is already really long as-is, and the fact that the link status is
exposed as a property is kinda irrelevant for kernel driver writers. But
up to you.
-Daniel

> +						 uint64_t link_status)
> +{
> +	struct drm_device *dev = connector->dev;
> +
> +	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
> +	connector->state->link_status = link_status;
> +	drm_modeset_unlock(&dev->mode_config.connection_mutex);
> +
> +}
> +EXPORT_SYMBOL(drm_mode_connector_set_link_status_property);
> +
>  int drm_mode_connector_set_obj_prop(struct drm_mode_object *obj,
>  				    struct drm_property *property,
>  				    uint64_t value)
> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> index 34f9741..53c5f70 100644
> --- a/include/drm/drm_connector.h
> +++ b/include/drm/drm_connector.h
> @@ -90,6 +90,17 @@ enum subpixel_order {
>  };
>  
>  /**
> + * enum drm_link_status - connector's link_status property value
> + *
> + * This enum is used as the connector's link status property value.
> + * It is set to the values defined in uapi.
> + */
> +enum drm_link_status {
> +	DRM_LINK_STATUS_GOOD = DRM_MODE_LINK_STATUS_GOOD,
> +	DRM_LINK_STATUS_BAD = DRM_MODE_LINK_STATUS_BAD,
> +};
> +
> +/**
>   * struct drm_display_info - runtime data about the connected sink
>   *
>   * Describes a given display (e.g. CRT or flat panel) and its limitations. For
> @@ -213,6 +224,12 @@ struct drm_connector_state {
>  
>  	struct drm_encoder *best_encoder;
>  
> +	/**
> +	 * @link_status: Connector link_status to keep track of whether link is
> +	 * GOOD or BAD to notify userspace if retraining is necessary.
> +	 */
> +	enum drm_link_status link_status;
> +
>  	struct drm_atomic_state *state;
>  };
>  
> @@ -773,6 +790,8 @@ int drm_mode_connector_set_path_property(struct drm_connector *connector,
>  int drm_mode_connector_set_tile_property(struct drm_connector *connector);
>  int drm_mode_connector_update_edid_property(struct drm_connector *connector,
>  					    const struct edid *edid);
> +void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
> +						 uint64_t link_status);
>  
>  /**
>   * struct drm_tile_group - Tile group metadata
> diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
> index bf9991b..86faee4 100644
> --- a/include/drm/drm_mode_config.h
> +++ b/include/drm/drm_mode_config.h
> @@ -431,6 +431,11 @@ struct drm_mode_config {
>  	 */
>  	struct drm_property *tile_property;
>  	/**
> +	 * @link_status_property: Default connector property for link status
> +	 * of a connector
> +	 */
> +	struct drm_property *link_status_property;
> +	/**
>  	 * @plane_type_property: Default plane property to differentiate
>  	 * CURSOR, PRIMARY and OVERLAY legacy uses of planes.
>  	 */
> diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
> index 728790b..309c478 100644
> --- a/include/uapi/drm/drm_mode.h
> +++ b/include/uapi/drm/drm_mode.h
> @@ -123,6 +123,10 @@
>  #define DRM_MODE_DIRTY_ON       1
>  #define DRM_MODE_DIRTY_ANNOTATE 2
>  
> +/* Link Status options */
> +#define DRM_MODE_LINK_STATUS_GOOD	0
> +#define DRM_MODE_LINK_STATUS_BAD	1
> +
>  struct drm_mode_modeinfo {
>  	__u32 clock;
>  	__u16 hdisplay;
> -- 
> 1.9.1
> 
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx

Re: [Intel-gfx] [PATCH 1/3] drm: Add a new connector atomic property for link status

[Manasi Navare]

On Fri, Dec 02, 2016 at 05:26:35PM +0100, Daniel Vetter wrote:
> On Tue, Nov 29, 2016 at 11:30:31PM -0800, Manasi Navare wrote:
> > At the time userspace does setcrtc, we've already promised the mode
> > would work. The promise is based on the theoretical capabilities of
> > the link, but it's possible we can't reach this in practice. The DP
> > spec describes how the link should be reduced, but we can't reduce
> > the link below the requirements of the mode. Black screen follows.
> > 
> > One idea would be to have setcrtc return a failure. However, it
> > already should not fail as the atomic checks have passed. It would
> > also conflict with the idea of making setcrtc asynchronous in the
> > future, returning before the actual mode setting and link training.
> > 
> > Another idea is to train the link "upfront" at hotplug time, before
> > pruning the mode list, so that we can do the pruning based on
> > practical not theoretical capabilities. However, the changes for link
> > training are pretty drastic, all for the sake of error handling and
> > DP compliance, when the most common happy day scenario is the current
> > approach of link training at mode setting time, using the optimal
> > parameters for the mode. It is also not certain all hardware could do
> > this without the pipe on; not even all our hardware can do this. Some
> > of this can be solved, but not trivially.
> > 
> > Both of the above ideas also fail to address link degradation *during*
> > operation.
> > 
> > The solution is to add a new "link-status" connector property in order
> > to address link training failure in a way that:
> > a) changes the current happy day scenario as little as possible, to
> > avoid regressions, b) can be implemented the same way by all drm
> > drivers, c) is still opt-in for the drivers and userspace, and opting
> > out doesn't regress the user experience, d) doesn't prevent drivers
> > from implementing better or alternate approaches, possibly without
> > userspace involvement. And, of course, handles all the issues presented.
> > In the usual happy day scenario, this is always "good". If something
> > fails during or after a mode set, the kernel driver can set the link
> > status to "bad" and issue a hotplug uevent for userspace to have it
> > re-check the valid modes through GET_CONNECTOR IOCTL, and try modeset
> > again. If the theoretical capabilities of the link can't be reached,
> > the mode list is trimmed based on that.
> > 
> > v4:
> > * Add comments in kernel-doc format (Daniel Vetter)
> > * Update the kernel-doc for link-status (Sean Paul)
> > v3:
> > * Fixed a build error (Jani Saarinen)
> > v2:
> > * Removed connector->link_status (Daniel Vetter)
> > * Set connector->state->link_status in drm_mode_connector_set_link_status_property
> > (Daniel Vetter)
> > * Set the connector_changed flag to true if connector->state->link_status changed.
> > * Reset link_status to GOOD in update_output_state (Daniel Vetter)
> > * Never allow userspace to set link status from Good To Bad (Daniel Vetter)
> > 
> > Acked-by: Tony Cheng <tony.cheng@amd.com>
> > Acked-by: Harry Wentland <harry.wentland@amd.com>
> > Cc: Jani Nikula <jani.nikula@linux.intel.com>
> > Cc: Daniel Vetter <daniel.vetter@intel.com>
> > Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > Cc: Sean Paul <seanpaul@chromium.org>
> > Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> > ---
> >  drivers/gpu/drm/drm_atomic.c        | 10 +++++++
> >  drivers/gpu/drm/drm_atomic_helper.c |  8 ++++++
> >  drivers/gpu/drm/drm_connector.c     | 54 ++++++++++++++++++++++++++++++++++++-
> >  include/drm/drm_connector.h         | 19 +++++++++++++
> >  include/drm/drm_mode_config.h       |  5 ++++
> >  include/uapi/drm/drm_mode.h         |  4 +++
> >  6 files changed, 99 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> > index 89737e4..990f013 100644
> > --- a/drivers/gpu/drm/drm_atomic.c
> > +++ b/drivers/gpu/drm/drm_atomic.c
> > @@ -1087,6 +1087,14 @@ int drm_atomic_connector_set_property(struct drm_connector *connector,
> >  		 * now?) atomic writes to DPMS property:
> >  		 */
> >  		return -EINVAL;
> > +	} else if (property == config->link_status_property) {
> > +		/* Never downgrade from GOOD to BAD on userspace's request here,
> > +		 * only hw issues can do that.
> > +		 */
> > +		if (state->link_status == DRM_LINK_STATUS_GOOD)
> > +			return 0;
> > +		state->link_status = val;
> > +		return 0;
> >  	} else if (connector->funcs->atomic_set_property) {
> >  		return connector->funcs->atomic_set_property(connector,
> >  				state, property, val);
> > @@ -1135,6 +1143,8 @@ static void drm_atomic_connector_print_state(struct drm_printer *p,
> >  		*val = (state->crtc) ? state->crtc->base.id : 0;
> >  	} else if (property == config->dpms_property) {
> >  		*val = connector->dpms;
> > +	} else if (property == config->link_status_property) {
> > +		*val = state->link_status;
> >  	} else if (connector->funcs->atomic_get_property) {
> >  		return connector->funcs->atomic_get_property(connector,
> >  				state, property, val);
> > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> > index 494680c..962ed66 100644
> > --- a/drivers/gpu/drm/drm_atomic_helper.c
> > +++ b/drivers/gpu/drm/drm_atomic_helper.c
> > @@ -519,6 +519,13 @@ static int handle_conflicting_encoders(struct drm_atomic_state *state,
> >  					       connector_state);
> >  		if (ret)
> >  			return ret;
> > +		if (connector->state->crtc) {
> > +			crtc_state = drm_atomic_get_existing_crtc_state(state,
> > +									connector->state->crtc);
> > +			if (connector->state->link_status !=
> > +			    connector_state->link_status)
> > +				crtc_state->connectors_changed = true;
> > +		}
> 
> See my previous review, this looks should imo be moved to a more obvious
> place than hidden deep down in the callchain.
> 
> >  	}

Yes I have looked at your previous review and this is inside drm_atomic_helper_check_modeset()
function just inside the connectors loop. Its not in the handle_conflicting_encoders function.
Its weird that in the diff it is showing up here. 
If you pull the patch you will see that it is written as follows:

for_each_connector_in_state(state, connector, connector_state, i) {
                /*
                 * This only sets crtc->connectors_changed for routing changes,
                 * drivers must set crtc->connectors_changed themselves when
                 * connector properties need to be updated.
                 */
                ret = update_connector_routing(state, connector,
                                               connector_state);
                if (ret)
                        return ret;
                if (connector->state->crtc) {
                        crtc_state = drm_atomic_get_existing_crtc_state(state,
                                                                        connector->state->crtc);
                        if (connector->state->link_status !=
                            connector_state->link_status)
                                crtc_state->connectors_changed = true;
                }
        }

Is this correct?

Manasi
> >  
> >  	/*
> > @@ -2258,6 +2265,7 @@ static int update_output_state(struct drm_atomic_state *state,
> >  								NULL);
> >  			if (ret)
> >  				return ret;
> > +			conn_state->link_status = DRM_LINK_STATUS_GOOD;
> 
> Iirc in our discussion we said a small comment here would be good, like
> 
> 			/* Make sure legacy setCrtc always re-trains. */
> 
> Might also be good to update the kernel-doc of
> drm_atomic_helper_set_config(). Something like
> 
>  * NOTE: For backwards compatibility with old userspace this automatically
>  * resets the "link-status" property to GOOD, to force any link
>  * re-training. The SETCRTC ioctl does not define whether an update does
>  * need a full modeset or just a plane update, hence we're allowed to do
>  * that. See also drm_mode_connector_set_link_status_property().
>  * 
> 
> >  		}
> >  	}
> >  
> > diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> > index 5a45262..8902367 100644
> > --- a/drivers/gpu/drm/drm_connector.c
> > +++ b/drivers/gpu/drm/drm_connector.c
> > @@ -243,6 +243,10 @@ int drm_connector_init(struct drm_device *dev,
> >  	drm_object_attach_property(&connector->base,
> >  				      config->dpms_property, 0);
> >  
> > +	drm_object_attach_property(&connector->base,
> > +				   config->link_status_property,
> > +				   0);
> > +
> >  	if (drm_core_check_feature(dev, DRIVER_ATOMIC)) {
> >  		drm_object_attach_property(&connector->base, config->prop_crtc_id, 0);
> >  	}
> > @@ -506,6 +510,12 @@ const char *drm_get_subpixel_order_name(enum subpixel_order order)
> >  };
> >  DRM_ENUM_NAME_FN(drm_get_dpms_name, drm_dpms_enum_list)
> >  
> > +static const struct drm_prop_enum_list drm_link_status_enum_list[] = {
> > +	{ DRM_MODE_LINK_STATUS_GOOD, "Good" },
> > +	{ DRM_MODE_LINK_STATUS_BAD, "Bad" },
> > +};
> > +DRM_ENUM_NAME_FN(drm_get_link_status_name, drm_link_status_enum_list)
> > +
> >  /**
> >   * drm_display_info_set_bus_formats - set the supported bus formats
> >   * @info: display info to store bus formats in
> > @@ -625,7 +635,11 @@ int drm_display_info_set_bus_formats(struct drm_display_info *info,
> >   * 	tiling and virtualize both &drm_crtc and &drm_plane if needed. Drivers
> >   * 	should update this value using drm_mode_connector_set_tile_property().
> >   * 	Userspace cannot change this property.
> > - *
> 
> One more from last round: Please leave this whitespace intact ...
> 
> > + * link-status:
> > + *      Connector link-status property to indicate the status of link. The default
> > + *      value of link-status is "GOOD". If something fails during or after modeset,
> > + *      the kernel driver may set this to "BAD" and issue a hotplug uevent. Drivers
> > + *      should update this value using drm_mode_connector_set_link_status_property().
> 
> ... and add an empty line here.
> 
> >   * Connectors also have one standardized atomic property:
> >   *
> >   * CRTC_ID:
> > @@ -666,6 +680,13 @@ int drm_connector_create_standard_properties(struct drm_device *dev)
> >  		return -ENOMEM;
> >  	dev->mode_config.tile_property = prop;
> >  
> > +	prop = drm_property_create_enum(dev, 0, "link-status",
> > +					drm_link_status_enum_list,
> > +					ARRAY_SIZE(drm_link_status_enum_list));
> > +	if (!prop)
> > +		return -ENOMEM;
> > +	dev->mode_config.link_status_property = prop;
> > +
> >  	return 0;
> >  }
> >  
> > @@ -995,6 +1016,37 @@ int drm_mode_connector_update_edid_property(struct drm_connector *connector,
> >  }
> >  EXPORT_SYMBOL(drm_mode_connector_update_edid_property);
> >  
> > +/**
> > + * drm_mode_connector_set_link_status_property - Set link status property of a connector
> > + * @connector: drm connector
> > + * @link_status: new value of link status property (0: Good, 1: Bad)
> > + *
> > + * In usual working scenario, this link status property will always be set to
> > + * "GOOD". If something fails during or after a mode set, the kernel driver
> > + * may set this link status property to "BAD". The caller then needs to send a
> > + * hotplug uevent for userspace to re-check the valid modes through
> > + * GET_CONNECTOR_IOCTL and retry modeset.
> > + *
> > + * Note: Drivers cannot rely on userspace to support this property and
> > + * issue a modeset. As such, they may choose to handle issues (like
> > + * re-training a link) without userspace's intervention.
> > + *
> > + * The reason for adding this property is to handle link training failures, but
> > + * it is not limited to DP or link training. For example, if we implement
> > + * asynchronous setcrtc, this property can be used to report any failures in that.
> > + */
> > +void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
> 
> Hm, tiny new bikeshed: I'd drop the _property postfix here. The function
> name is already really long as-is, and the fact that the link status is
> exposed as a property is kinda irrelevant for kernel driver writers. But
> up to you.
> -Daniel
> 
> > +						 uint64_t link_status)
> > +{
> > +	struct drm_device *dev = connector->dev;
> > +
> > +	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
> > +	connector->state->link_status = link_status;
> > +	drm_modeset_unlock(&dev->mode_config.connection_mutex);
> > +
> > +}
> > +EXPORT_SYMBOL(drm_mode_connector_set_link_status_property);
> > +
> >  int drm_mode_connector_set_obj_prop(struct drm_mode_object *obj,
> >  				    struct drm_property *property,
> >  				    uint64_t value)
> > diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> > index 34f9741..53c5f70 100644
> > --- a/include/drm/drm_connector.h
> > +++ b/include/drm/drm_connector.h
> > @@ -90,6 +90,17 @@ enum subpixel_order {
> >  };
> >  
> >  /**
> > + * enum drm_link_status - connector's link_status property value
> > + *
> > + * This enum is used as the connector's link status property value.
> > + * It is set to the values defined in uapi.
> > + */
> > +enum drm_link_status {
> > +	DRM_LINK_STATUS_GOOD = DRM_MODE_LINK_STATUS_GOOD,
> > +	DRM_LINK_STATUS_BAD = DRM_MODE_LINK_STATUS_BAD,
> > +};
> > +
> > +/**
> >   * struct drm_display_info - runtime data about the connected sink
> >   *
> >   * Describes a given display (e.g. CRT or flat panel) and its limitations. For
> > @@ -213,6 +224,12 @@ struct drm_connector_state {
> >  
> >  	struct drm_encoder *best_encoder;
> >  
> > +	/**
> > +	 * @link_status: Connector link_status to keep track of whether link is
> > +	 * GOOD or BAD to notify userspace if retraining is necessary.
> > +	 */
> > +	enum drm_link_status link_status;
> > +
> >  	struct drm_atomic_state *state;
> >  };
> >  
> > @@ -773,6 +790,8 @@ int drm_mode_connector_set_path_property(struct drm_connector *connector,
> >  int drm_mode_connector_set_tile_property(struct drm_connector *connector);
> >  int drm_mode_connector_update_edid_property(struct drm_connector *connector,
> >  					    const struct edid *edid);
> > +void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
> > +						 uint64_t link_status);
> >  
> >  /**
> >   * struct drm_tile_group - Tile group metadata
> > diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
> > index bf9991b..86faee4 100644
> > --- a/include/drm/drm_mode_config.h
> > +++ b/include/drm/drm_mode_config.h
> > @@ -431,6 +431,11 @@ struct drm_mode_config {
> >  	 */
> >  	struct drm_property *tile_property;
> >  	/**
> > +	 * @link_status_property: Default connector property for link status
> > +	 * of a connector
> > +	 */
> > +	struct drm_property *link_status_property;
> > +	/**
> >  	 * @plane_type_property: Default plane property to differentiate
> >  	 * CURSOR, PRIMARY and OVERLAY legacy uses of planes.
> >  	 */
> > diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
> > index 728790b..309c478 100644
> > --- a/include/uapi/drm/drm_mode.h
> > +++ b/include/uapi/drm/drm_mode.h
> > @@ -123,6 +123,10 @@
> >  #define DRM_MODE_DIRTY_ON       1
> >  #define DRM_MODE_DIRTY_ANNOTATE 2
> >  
> > +/* Link Status options */
> > +#define DRM_MODE_LINK_STATUS_GOOD	0
> > +#define DRM_MODE_LINK_STATUS_BAD	1
> > +
> >  struct drm_mode_modeinfo {
> >  	__u32 clock;
> >  	__u16 hdisplay;
> > -- 
> > 1.9.1
> > 
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
_______________________________________________
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Re: [Intel-gfx] [PATCH 1/3] drm: Add a new connector atomic property for link status

[Daniel Vetter]

On Fri, Dec 02, 2016 at 09:48:59AM -0800, Manasi Navare wrote:
> On Fri, Dec 02, 2016 at 05:26:35PM +0100, Daniel Vetter wrote:
> > On Tue, Nov 29, 2016 at 11:30:31PM -0800, Manasi Navare wrote:
> > > At the time userspace does setcrtc, we've already promised the mode
> > > would work. The promise is based on the theoretical capabilities of
> > > the link, but it's possible we can't reach this in practice. The DP
> > > spec describes how the link should be reduced, but we can't reduce
> > > the link below the requirements of the mode. Black screen follows.
> > > 
> > > One idea would be to have setcrtc return a failure. However, it
> > > already should not fail as the atomic checks have passed. It would
> > > also conflict with the idea of making setcrtc asynchronous in the
> > > future, returning before the actual mode setting and link training.
> > > 
> > > Another idea is to train the link "upfront" at hotplug time, before
> > > pruning the mode list, so that we can do the pruning based on
> > > practical not theoretical capabilities. However, the changes for link
> > > training are pretty drastic, all for the sake of error handling and
> > > DP compliance, when the most common happy day scenario is the current
> > > approach of link training at mode setting time, using the optimal
> > > parameters for the mode. It is also not certain all hardware could do
> > > this without the pipe on; not even all our hardware can do this. Some
> > > of this can be solved, but not trivially.
> > > 
> > > Both of the above ideas also fail to address link degradation *during*
> > > operation.
> > > 
> > > The solution is to add a new "link-status" connector property in order
> > > to address link training failure in a way that:
> > > a) changes the current happy day scenario as little as possible, to
> > > avoid regressions, b) can be implemented the same way by all drm
> > > drivers, c) is still opt-in for the drivers and userspace, and opting
> > > out doesn't regress the user experience, d) doesn't prevent drivers
> > > from implementing better or alternate approaches, possibly without
> > > userspace involvement. And, of course, handles all the issues presented.
> > > In the usual happy day scenario, this is always "good". If something
> > > fails during or after a mode set, the kernel driver can set the link
> > > status to "bad" and issue a hotplug uevent for userspace to have it
> > > re-check the valid modes through GET_CONNECTOR IOCTL, and try modeset
> > > again. If the theoretical capabilities of the link can't be reached,
> > > the mode list is trimmed based on that.
> > > 
> > > v4:
> > > * Add comments in kernel-doc format (Daniel Vetter)
> > > * Update the kernel-doc for link-status (Sean Paul)
> > > v3:
> > > * Fixed a build error (Jani Saarinen)
> > > v2:
> > > * Removed connector->link_status (Daniel Vetter)
> > > * Set connector->state->link_status in drm_mode_connector_set_link_status_property
> > > (Daniel Vetter)
> > > * Set the connector_changed flag to true if connector->state->link_status changed.
> > > * Reset link_status to GOOD in update_output_state (Daniel Vetter)
> > > * Never allow userspace to set link status from Good To Bad (Daniel Vetter)
> > > 
> > > Acked-by: Tony Cheng <tony.cheng@amd.com>
> > > Acked-by: Harry Wentland <harry.wentland@amd.com>
> > > Cc: Jani Nikula <jani.nikula@linux.intel.com>
> > > Cc: Daniel Vetter <daniel.vetter@intel.com>
> > > Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> > > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > > Cc: Sean Paul <seanpaul@chromium.org>
> > > Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> > > ---
> > >  drivers/gpu/drm/drm_atomic.c        | 10 +++++++
> > >  drivers/gpu/drm/drm_atomic_helper.c |  8 ++++++
> > >  drivers/gpu/drm/drm_connector.c     | 54 ++++++++++++++++++++++++++++++++++++-
> > >  include/drm/drm_connector.h         | 19 +++++++++++++
> > >  include/drm/drm_mode_config.h       |  5 ++++
> > >  include/uapi/drm/drm_mode.h         |  4 +++
> > >  6 files changed, 99 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> > > index 89737e4..990f013 100644
> > > --- a/drivers/gpu/drm/drm_atomic.c
> > > +++ b/drivers/gpu/drm/drm_atomic.c
> > > @@ -1087,6 +1087,14 @@ int drm_atomic_connector_set_property(struct drm_connector *connector,
> > >  		 * now?) atomic writes to DPMS property:
> > >  		 */
> > >  		return -EINVAL;
> > > +	} else if (property == config->link_status_property) {
> > > +		/* Never downgrade from GOOD to BAD on userspace's request here,
> > > +		 * only hw issues can do that.
> > > +		 */
> > > +		if (state->link_status == DRM_LINK_STATUS_GOOD)
> > > +			return 0;
> > > +		state->link_status = val;
> > > +		return 0;
> > >  	} else if (connector->funcs->atomic_set_property) {
> > >  		return connector->funcs->atomic_set_property(connector,
> > >  				state, property, val);
> > > @@ -1135,6 +1143,8 @@ static void drm_atomic_connector_print_state(struct drm_printer *p,
> > >  		*val = (state->crtc) ? state->crtc->base.id : 0;
> > >  	} else if (property == config->dpms_property) {
> > >  		*val = connector->dpms;
> > > +	} else if (property == config->link_status_property) {
> > > +		*val = state->link_status;
> > >  	} else if (connector->funcs->atomic_get_property) {
> > >  		return connector->funcs->atomic_get_property(connector,
> > >  				state, property, val);
> > > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> > > index 494680c..962ed66 100644
> > > --- a/drivers/gpu/drm/drm_atomic_helper.c
> > > +++ b/drivers/gpu/drm/drm_atomic_helper.c
> > > @@ -519,6 +519,13 @@ static int handle_conflicting_encoders(struct drm_atomic_state *state,
> > >  					       connector_state);
> > >  		if (ret)
> > >  			return ret;
> > > +		if (connector->state->crtc) {
> > > +			crtc_state = drm_atomic_get_existing_crtc_state(state,
> > > +									connector->state->crtc);
> > > +			if (connector->state->link_status !=
> > > +			    connector_state->link_status)
> > > +				crtc_state->connectors_changed = true;
> > > +		}
> > 
> > See my previous review, this looks should imo be moved to a more obvious
> > place than hidden deep down in the callchain.
> > 
> > >  	}
> 
> Yes I have looked at your previous review and this is inside drm_atomic_helper_check_modeset()
> function just inside the connectors loop. Its not in the handle_conflicting_encoders function.
> Its weird that in the diff it is showing up here. 
> If you pull the patch you will see that it is written as follows:
> 
> for_each_connector_in_state(state, connector, connector_state, i) {
>                 /*
>                  * This only sets crtc->connectors_changed for routing changes,
>                  * drivers must set crtc->connectors_changed themselves when
>                  * connector properties need to be updated.
>                  */
>                 ret = update_connector_routing(state, connector,
>                                                connector_state);
>                 if (ret)
>                         return ret;
>                 if (connector->state->crtc) {
>                         crtc_state = drm_atomic_get_existing_crtc_state(state,
>                                                                         connector->state->crtc);
>                         if (connector->state->link_status !=
>                             connector_state->link_status)
>                                 crtc_state->connectors_changed = true;
>                 }
>         }
> 
> Is this correct?

Yup, double checked myself, no idea what git diff is doing here thinking
it's in a different function ...
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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Re: [PATCH 1/3] drm: Add a new connector atomic property for link status

[Manasi Navare]

On Fri, Dec 02, 2016 at 05:26:35PM +0100, Daniel Vetter wrote:
> On Tue, Nov 29, 2016 at 11:30:31PM -0800, Manasi Navare wrote:
> > At the time userspace does setcrtc, we've already promised the mode
> > would work. The promise is based on the theoretical capabilities of
> > the link, but it's possible we can't reach this in practice. The DP
> > spec describes how the link should be reduced, but we can't reduce
> > the link below the requirements of the mode. Black screen follows.
> > 
> > One idea would be to have setcrtc return a failure. However, it
> > already should not fail as the atomic checks have passed. It would
> > also conflict with the idea of making setcrtc asynchronous in the
> > future, returning before the actual mode setting and link training.
> > 
> > Another idea is to train the link "upfront" at hotplug time, before
> > pruning the mode list, so that we can do the pruning based on
> > practical not theoretical capabilities. However, the changes for link
> > training are pretty drastic, all for the sake of error handling and
> > DP compliance, when the most common happy day scenario is the current
> > approach of link training at mode setting time, using the optimal
> > parameters for the mode. It is also not certain all hardware could do
> > this without the pipe on; not even all our hardware can do this. Some
> > of this can be solved, but not trivially.
> > 
> > Both of the above ideas also fail to address link degradation *during*
> > operation.
> > 
> > The solution is to add a new "link-status" connector property in order
> > to address link training failure in a way that:
> > a) changes the current happy day scenario as little as possible, to
> > avoid regressions, b) can be implemented the same way by all drm
> > drivers, c) is still opt-in for the drivers and userspace, and opting
> > out doesn't regress the user experience, d) doesn't prevent drivers
> > from implementing better or alternate approaches, possibly without
> > userspace involvement. And, of course, handles all the issues presented.
> > In the usual happy day scenario, this is always "good". If something
> > fails during or after a mode set, the kernel driver can set the link
> > status to "bad" and issue a hotplug uevent for userspace to have it
> > re-check the valid modes through GET_CONNECTOR IOCTL, and try modeset
> > again. If the theoretical capabilities of the link can't be reached,
> > the mode list is trimmed based on that.
> > 
> > v4:
> > * Add comments in kernel-doc format (Daniel Vetter)
> > * Update the kernel-doc for link-status (Sean Paul)
> > v3:
> > * Fixed a build error (Jani Saarinen)
> > v2:
> > * Removed connector->link_status (Daniel Vetter)
> > * Set connector->state->link_status in drm_mode_connector_set_link_status_property
> > (Daniel Vetter)
> > * Set the connector_changed flag to true if connector->state->link_status changed.
> > * Reset link_status to GOOD in update_output_state (Daniel Vetter)
> > * Never allow userspace to set link status from Good To Bad (Daniel Vetter)
> > 
> > Acked-by: Tony Cheng <tony.cheng@amd.com>
> > Acked-by: Harry Wentland <harry.wentland@amd.com>
> > Cc: Jani Nikula <jani.nikula@linux.intel.com>
> > Cc: Daniel Vetter <daniel.vetter@intel.com>
> > Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > Cc: Sean Paul <seanpaul@chromium.org>
> > Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> > ---
> >  drivers/gpu/drm/drm_atomic.c        | 10 +++++++
> >  drivers/gpu/drm/drm_atomic_helper.c |  8 ++++++
> >  drivers/gpu/drm/drm_connector.c     | 54 ++++++++++++++++++++++++++++++++++++-
> >  include/drm/drm_connector.h         | 19 +++++++++++++
> >  include/drm/drm_mode_config.h       |  5 ++++
> >  include/uapi/drm/drm_mode.h         |  4 +++
> >  6 files changed, 99 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> > index 89737e4..990f013 100644
> > --- a/drivers/gpu/drm/drm_atomic.c
> > +++ b/drivers/gpu/drm/drm_atomic.c
> > @@ -1087,6 +1087,14 @@ int drm_atomic_connector_set_property(struct drm_connector *connector,
> >  		 * now?) atomic writes to DPMS property:
> >  		 */
> >  		return -EINVAL;
> > +	} else if (property == config->link_status_property) {
> > +		/* Never downgrade from GOOD to BAD on userspace's request here,
> > +		 * only hw issues can do that.
> > +		 */
> > +		if (state->link_status == DRM_LINK_STATUS_GOOD)
> > +			return 0;
> > +		state->link_status = val;
> > +		return 0;
> >  	} else if (connector->funcs->atomic_set_property) {
> >  		return connector->funcs->atomic_set_property(connector,
> >  				state, property, val);
> > @@ -1135,6 +1143,8 @@ static void drm_atomic_connector_print_state(struct drm_printer *p,
> >  		*val = (state->crtc) ? state->crtc->base.id : 0;
> >  	} else if (property == config->dpms_property) {
> >  		*val = connector->dpms;
> > +	} else if (property == config->link_status_property) {
> > +		*val = state->link_status;
> >  	} else if (connector->funcs->atomic_get_property) {
> >  		return connector->funcs->atomic_get_property(connector,
> >  				state, property, val);
> > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> > index 494680c..962ed66 100644
> > --- a/drivers/gpu/drm/drm_atomic_helper.c
> > +++ b/drivers/gpu/drm/drm_atomic_helper.c
> > @@ -519,6 +519,13 @@ static int handle_conflicting_encoders(struct drm_atomic_state *state,
> >  					       connector_state);
> >  		if (ret)
> >  			return ret;
> > +		if (connector->state->crtc) {
> > +			crtc_state = drm_atomic_get_existing_crtc_state(state,
> > +									connector->state->crtc);
> > +			if (connector->state->link_status !=
> > +			    connector_state->link_status)
> > +				crtc_state->connectors_changed = true;
> > +		}
> 
> See my previous review, this looks should imo be moved to a more obvious
> place than hidden deep down in the callchain.
> 
> >  	}
> >  
> >  	/*
> > @@ -2258,6 +2265,7 @@ static int update_output_state(struct drm_atomic_state *state,
> >  								NULL);
> >  			if (ret)
> >  				return ret;
> > +			conn_state->link_status = DRM_LINK_STATUS_GOOD;
> 
> Iirc in our discussion we said a small comment here would be good, like
> 
> 			/* Make sure legacy setCrtc always re-trains. */
> 
> Might also be good to update the kernel-doc of
> drm_atomic_helper_set_config(). Something like
> 
>  * NOTE: For backwards compatibility with old userspace this automatically
>  * resets the "link-status" property to GOOD, to force any link
>  * re-training. The SETCRTC ioctl does not define whether an update does
>  * need a full modeset or just a plane update, hence we're allowed to do
>  * that. See also drm_mode_connector_set_link_status_property().
>  * 
> 
> >  		}
> >  	}
> >  
> > diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> > index 5a45262..8902367 100644
> > --- a/drivers/gpu/drm/drm_connector.c
> > +++ b/drivers/gpu/drm/drm_connector.c
> > @@ -243,6 +243,10 @@ int drm_connector_init(struct drm_device *dev,
> >  	drm_object_attach_property(&connector->base,
> >  				      config->dpms_property, 0);
> >  
> > +	drm_object_attach_property(&connector->base,
> > +				   config->link_status_property,
> > +				   0);
> > +
> >  	if (drm_core_check_feature(dev, DRIVER_ATOMIC)) {
> >  		drm_object_attach_property(&connector->base, config->prop_crtc_id, 0);
> >  	}
> > @@ -506,6 +510,12 @@ const char *drm_get_subpixel_order_name(enum subpixel_order order)
> >  };
> >  DRM_ENUM_NAME_FN(drm_get_dpms_name, drm_dpms_enum_list)
> >  
> > +static const struct drm_prop_enum_list drm_link_status_enum_list[] = {
> > +	{ DRM_MODE_LINK_STATUS_GOOD, "Good" },
> > +	{ DRM_MODE_LINK_STATUS_BAD, "Bad" },
> > +};
> > +DRM_ENUM_NAME_FN(drm_get_link_status_name, drm_link_status_enum_list)
> > +
> >  /**
> >   * drm_display_info_set_bus_formats - set the supported bus formats
> >   * @info: display info to store bus formats in
> > @@ -625,7 +635,11 @@ int drm_display_info_set_bus_formats(struct drm_display_info *info,
> >   * 	tiling and virtualize both &drm_crtc and &drm_plane if needed. Drivers
> >   * 	should update this value using drm_mode_connector_set_tile_property().
> >   * 	Userspace cannot change this property.
> > - *
> 
> One more from last round: Please leave this whitespace intact ...
> 
> > + * link-status:
> > + *      Connector link-status property to indicate the status of link. The default
> > + *      value of link-status is "GOOD". If something fails during or after modeset,
> > + *      the kernel driver may set this to "BAD" and issue a hotplug uevent. Drivers
> > + *      should update this value using drm_mode_connector_set_link_status_property().
> 
> ... and add an empty line here.
> 
> >   * Connectors also have one standardized atomic property:
> >   *
> >   * CRTC_ID:
> > @@ -666,6 +680,13 @@ int drm_connector_create_standard_properties(struct drm_device *dev)
> >  		return -ENOMEM;
> >  	dev->mode_config.tile_property = prop;
> >  
> > +	prop = drm_property_create_enum(dev, 0, "link-status",
> > +					drm_link_status_enum_list,
> > +					ARRAY_SIZE(drm_link_status_enum_list));
> > +	if (!prop)
> > +		return -ENOMEM;
> > +	dev->mode_config.link_status_property = prop;
> > +
> >  	return 0;
> >  }
> >  
> > @@ -995,6 +1016,37 @@ int drm_mode_connector_update_edid_property(struct drm_connector *connector,
> >  }
> >  EXPORT_SYMBOL(drm_mode_connector_update_edid_property);
> >  
> > +/**
> > + * drm_mode_connector_set_link_status_property - Set link status property of a connector
> > + * @connector: drm connector
> > + * @link_status: new value of link status property (0: Good, 1: Bad)
> > + *
> > + * In usual working scenario, this link status property will always be set to
> > + * "GOOD". If something fails during or after a mode set, the kernel driver
> > + * may set this link status property to "BAD". The caller then needs to send a
> > + * hotplug uevent for userspace to re-check the valid modes through
> > + * GET_CONNECTOR_IOCTL and retry modeset.
> > + *
> > + * Note: Drivers cannot rely on userspace to support this property and
> > + * issue a modeset. As such, they may choose to handle issues (like
> > + * re-training a link) without userspace's intervention.
> > + *
> > + * The reason for adding this property is to handle link training failures, but
> > + * it is not limited to DP or link training. For example, if we implement
> > + * asynchronous setcrtc, this property can be used to report any failures in that.
> > + */
> > +void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
> 
> Hm, tiny new bikeshed: I'd drop the _property postfix here. The function
> name is already really long as-is, and the fact that the link status is
> exposed as a property is kinda irrelevant for kernel driver writers. But
> up to you.
> -Daniel
>

I decided to name it as drm_mode_connector_set_link_status_property()
looking at names of other set_property functions like
drm_mode_connector_update_edid_property() or drm_mode_connector_set_path_property().
Thats why I think it makes sense to append it with property just to be consistent.

Manasi

 
> > +						 uint64_t link_status)
> > +{
> > +	struct drm_device *dev = connector->dev;
> > +
> > +	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
> > +	connector->state->link_status = link_status;
> > +	drm_modeset_unlock(&dev->mode_config.connection_mutex);
> > +
> > +}
> > +EXPORT_SYMBOL(drm_mode_connector_set_link_status_property);
> > +
> >  int drm_mode_connector_set_obj_prop(struct drm_mode_object *obj,
> >  				    struct drm_property *property,
> >  				    uint64_t value)
> > diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> > index 34f9741..53c5f70 100644
> > --- a/include/drm/drm_connector.h
> > +++ b/include/drm/drm_connector.h
> > @@ -90,6 +90,17 @@ enum subpixel_order {
> >  };
> >  
> >  /**
> > + * enum drm_link_status - connector's link_status property value
> > + *
> > + * This enum is used as the connector's link status property value.
> > + * It is set to the values defined in uapi.
> > + */
> > +enum drm_link_status {
> > +	DRM_LINK_STATUS_GOOD = DRM_MODE_LINK_STATUS_GOOD,
> > +	DRM_LINK_STATUS_BAD = DRM_MODE_LINK_STATUS_BAD,
> > +};
> > +
> > +/**
> >   * struct drm_display_info - runtime data about the connected sink
> >   *
> >   * Describes a given display (e.g. CRT or flat panel) and its limitations. For
> > @@ -213,6 +224,12 @@ struct drm_connector_state {
> >  
> >  	struct drm_encoder *best_encoder;
> >  
> > +	/**
> > +	 * @link_status: Connector link_status to keep track of whether link is
> > +	 * GOOD or BAD to notify userspace if retraining is necessary.
> > +	 */
> > +	enum drm_link_status link_status;
> > +
> >  	struct drm_atomic_state *state;
> >  };
> >  
> > @@ -773,6 +790,8 @@ int drm_mode_connector_set_path_property(struct drm_connector *connector,
> >  int drm_mode_connector_set_tile_property(struct drm_connector *connector);
> >  int drm_mode_connector_update_edid_property(struct drm_connector *connector,
> >  					    const struct edid *edid);
> > +void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
> > +						 uint64_t link_status);
> >  
> >  /**
> >   * struct drm_tile_group - Tile group metadata
> > diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
> > index bf9991b..86faee4 100644
> > --- a/include/drm/drm_mode_config.h
> > +++ b/include/drm/drm_mode_config.h
> > @@ -431,6 +431,11 @@ struct drm_mode_config {
> >  	 */
> >  	struct drm_property *tile_property;
> >  	/**
> > +	 * @link_status_property: Default connector property for link status
> > +	 * of a connector
> > +	 */
> > +	struct drm_property *link_status_property;
> > +	/**
> >  	 * @plane_type_property: Default plane property to differentiate
> >  	 * CURSOR, PRIMARY and OVERLAY legacy uses of planes.
> >  	 */
> > diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
> > index 728790b..309c478 100644
> > --- a/include/uapi/drm/drm_mode.h
> > +++ b/include/uapi/drm/drm_mode.h
> > @@ -123,6 +123,10 @@
> >  #define DRM_MODE_DIRTY_ON       1
> >  #define DRM_MODE_DIRTY_ANNOTATE 2
> >  
> > +/* Link Status options */
> > +#define DRM_MODE_LINK_STATUS_GOOD	0
> > +#define DRM_MODE_LINK_STATUS_BAD	1
> > +
> >  struct drm_mode_modeinfo {
> >  	__u32 clock;
> >  	__u16 hdisplay;
> > -- 
> > 1.9.1
> > 
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
> _______________________________________________
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> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
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Re: [PATCH 1/3] drm: Add a new connector atomic property for link status

[Daniel Vetter]

On Mon, Dec 05, 2016 at 12:33:28PM -0800, Manasi Navare wrote:
> On Fri, Dec 02, 2016 at 05:26:35PM +0100, Daniel Vetter wrote:
> > Hm, tiny new bikeshed: I'd drop the _property postfix here. The function
> > name is already really long as-is, and the fact that the link status is
> > exposed as a property is kinda irrelevant for kernel driver writers. But
> > up to you.
> > -Daniel
> >
> 
> I decided to name it as drm_mode_connector_set_link_status_property()
> looking at names of other set_property functions like
> drm_mode_connector_update_edid_property() or drm_mode_connector_set_path_property().
> Thats why I think it makes sense to append it with property just to be consistent.

Yeah it's fine either way, maybe we could just drop _property from all of
them. Really doesn't add much, but these long function names make
reasonable code layout a pain. Anyway, nothing that must be done here,
agreed.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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