[PATCH 00/15] DSC MST support for AMDGPU

[PATCH 00/15] DSC MST support for AMDGPU

[mikita.lipski-5C7GfCeVMHo]

From: Mikita Lipski <mikita.lipski@amd.com>

This set of patches is a continuation of DSC enablement
patches for AMDGPU. This set enables DSC on MST.

First 3 patches add atomic check functionality to
encoder and connector to allocate and release VCPI
slots on each state atomic check. These changes
utilize newly added drm_mst_helper functions for
better tracking of VCPI slots.

Other 12 patches have been introduced in multiple
iterations to the mailing list before. These patches were
developed by David Francis as part of his work on DSC.

David Francis (12):
  drm/dp_mst: Add PBN calculation for DSC modes
  drm/dp_mst: Parse FEC capability on MST ports
  drm/dp_mst: Add MST support to DP DPCD R/W functions
  drm/dp_mst: Fill branch->num_ports
  drm/dp_mst: Add helpers for MST DSC and virtual DPCD aux
  drm/dp_mst: Add new quirk for Synaptics MST hubs
  drm/amd/display: Use correct helpers to compute timeslots
  drm/amd/display: Initialize DSC PPS variables to 0
  drm/amd/display: Validate DSC caps on MST endpoints
  drm/amd/display: Write DSC enable to MST DPCD
  drm/amd/display: MST DSC compute fair share
  drm/amd/display: Trigger modesets on MST DSC connectors

Mikita Lipski (3):
  drm/amdgpu: Add encoder atomic check
  drm/amdgpu: Add connector atomic check
  drm/amdgpu: validate mst topology in atomic check

 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 153 ++++++
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h |   3 +
 .../amd/display/amdgpu_dm/amdgpu_dm_helpers.c |  37 +-
 .../display/amdgpu_dm/amdgpu_dm_mst_types.c   | 451 +++++++++++++++++-
 .../display/amdgpu_dm/amdgpu_dm_mst_types.h   |   4 +
 .../drm/amd/display/dc/core/dc_link_hwss.c    |   3 +
 .../gpu/drm/amd/display/dc/dcn20/dcn20_dsc.c  |   3 +
 .../drm/amd/display/dc/dcn20/dcn20_resource.c |   7 +-
 .../drm/amd/display/dc/dcn20/dcn20_resource.h |   1 +
 drivers/gpu/drm/drm_dp_aux_dev.c              |  12 +-
 drivers/gpu/drm/drm_dp_helper.c               |  34 +-
 drivers/gpu/drm/drm_dp_mst_topology.c         | 174 ++++++-
 drivers/gpu/drm/i915/intel_dp_mst.c           |   3 +-
 drivers/gpu/drm/nouveau/dispnv50/disp.c       |   3 +-
 drivers/gpu/drm/radeon/radeon_dp_mst.c        |   2 +-
 include/drm/drm_dp_helper.h                   |   7 +
 include/drm/drm_dp_mst_helper.h               |   8 +-
 17 files changed, 866 insertions(+), 39 deletions(-)

-- 
2.17.1

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[PATCH 02/15] drm/amdgpu: Add connector atomic check

[mikita.lipski]

From: Mikita Lipski <mikita.lipski@amd.com>

[why]
Complying with new MST atomic check requirements.
The driver needs to call this function on every
atomic check to reset the VCPI slots if new state
disables
[how]
- Verify that it is a MST connection
- Verify that old crtc state exists
- Verify the new crtc state disables sink
- Release VCPI slots on the port

Cc: Lyude Paul <lyude@redhat.com>
Signed-off-by: Mikita Lipski <mikita.lipski@amd.com>
---
 .../display/amdgpu_dm/amdgpu_dm_mst_types.c   | 34 +++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
index 16218a202b59..4e1bbf5bbe77 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
@@ -252,10 +252,44 @@ static struct drm_encoder *dm_mst_best_encoder(struct drm_connector *connector)
 	return &amdgpu_dm_connector->mst_encoder->base;
 }
 
+static int dm_dp_mst_atomic_check(struct drm_connector *connector,
+				struct drm_connector_state *new_conn_state)
+{
+	struct drm_atomic_state *state = new_conn_state->state;
+	struct drm_connector_state *old_conn_state =
+			drm_atomic_get_old_connector_state(state, connector);
+	struct amdgpu_dm_connector *aconnector = to_amdgpu_dm_connector(connector);
+	struct drm_crtc_state *new_crtc_state;
+	struct drm_dp_mst_topology_mgr *mst_mgr;
+	struct drm_dp_mst_port *mst_port;
+
+	if (!aconnector || !aconnector->port)
+		return 0;
+
+	mst_port = aconnector->port;
+	mst_mgr = &aconnector->mst_port->mst_mgr;
+
+	if (!old_conn_state->crtc)
+		return 0;
+
+	if (new_conn_state->crtc) {
+		new_crtc_state = drm_atomic_get_old_crtc_state(state, new_conn_state->crtc);
+		if (!new_crtc_state ||
+		    !drm_atomic_crtc_needs_modeset(new_crtc_state) ||
+		    new_crtc_state->enable)
+			return 0;
+		}
+
+	return drm_dp_atomic_release_vcpi_slots(state,
+						mst_mgr,
+						mst_port);
+}
+
 static const struct drm_connector_helper_funcs dm_dp_mst_connector_helper_funcs = {
 	.get_modes = dm_dp_mst_get_modes,
 	.mode_valid = amdgpu_dm_connector_mode_valid,
 	.best_encoder = dm_mst_best_encoder,
+	.atomic_check = dm_dp_mst_atomic_check,
 };
 
 static void amdgpu_dm_encoder_destroy(struct drm_encoder *encoder)
-- 
2.17.1

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Re: [PATCH 02/15] drm/amdgpu: Add connector atomic check

[Lyude Paul]

On Wed, 2019-09-18 at 16:26 -0400, mikita.lipski@amd.com wrote:
> From: Mikita Lipski <mikita.lipski@amd.com>
> 
> [why]
> Complying with new MST atomic check requirements.
> The driver needs to call this function on every
> atomic check to reset the VCPI slots if new state
> disables
> [how]
> - Verify that it is a MST connection
> - Verify that old crtc state exists
> - Verify the new crtc state disables sink
> - Release VCPI slots on the port
> 
> Cc: Lyude Paul <lyude@redhat.com>
> Signed-off-by: Mikita Lipski <mikita.lipski@amd.com>
> ---
>  .../display/amdgpu_dm/amdgpu_dm_mst_types.c   | 34 +++++++++++++++++++
>  1 file changed, 34 insertions(+)
> 
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> index 16218a202b59..4e1bbf5bbe77 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> @@ -252,10 +252,44 @@ static struct drm_encoder *dm_mst_best_encoder(struct
> drm_connector *connector)
>  	return &amdgpu_dm_connector->mst_encoder->base;
>  }
>  
> +static int dm_dp_mst_atomic_check(struct drm_connector *connector,
> +				struct drm_connector_state *new_conn_state)
> +{
> +	struct drm_atomic_state *state = new_conn_state->state;
> +	struct drm_connector_state *old_conn_state =
> +			drm_atomic_get_old_connector_state(state, connector);
> +	struct amdgpu_dm_connector *aconnector =
> to_amdgpu_dm_connector(connector);
> +	struct drm_crtc_state *new_crtc_state;
> +	struct drm_dp_mst_topology_mgr *mst_mgr;
> +	struct drm_dp_mst_port *mst_port;
> +
> +	if (!aconnector || !aconnector->port)
> +		return 0;
Same as the last patch, I don't think you should need either of these checks.

Otherwise, assuming this gets squashed into the previous patch this looks fine
to me

> +
> +	mst_port = aconnector->port;
> +	mst_mgr = &aconnector->mst_port->mst_mgr;
> +
> +	if (!old_conn_state->crtc)
> +		return 0;
> +
> +	if (new_conn_state->crtc) {
> +		new_crtc_state = drm_atomic_get_old_crtc_state(state,
> new_conn_state->crtc);
> +		if (!new_crtc_state ||
> +		    !drm_atomic_crtc_needs_modeset(new_crtc_state) ||
> +		    new_crtc_state->enable)
> +			return 0;
> +		}
> +
> +	return drm_dp_atomic_release_vcpi_slots(state,
> +						mst_mgr,
> +						mst_port);
> +}
> +
>  static const struct drm_connector_helper_funcs
> dm_dp_mst_connector_helper_funcs = {
>  	.get_modes = dm_dp_mst_get_modes,
>  	.mode_valid = amdgpu_dm_connector_mode_valid,
>  	.best_encoder = dm_mst_best_encoder,
> +	.atomic_check = dm_dp_mst_atomic_check,
>  };
>  
>  static void amdgpu_dm_encoder_destroy(struct drm_encoder *encoder)
-- 
Cheers,
	Lyude Paul

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[PATCH 08/15] drm/dp_mst: Add helpers for MST DSC and virtual DPCD aux

[mikita.lipski]

From: David Francis <David.Francis@amd.com>

Add drm_dp_mst_dsc_aux_for_port. To enable DSC, the DSC_ENABLED
register might have to be written on the leaf port's DPCD,
its parent's DPCD, or the MST manager's DPCD. This function
finds the correct aux for the job.

As part of this, add drm_dp_mst_is_virtual_dpcd. Virtual DPCD
is a DP feature new in DP v1.4, which exposes certain DPCD
registers on virtual ports.

v2: Remember to unlock mutex on all paths
v3: Refactor to match coding style and increase brevity

Cc: Lyude Paul <lyude@redhat.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com>
Signed-off-by: David Francis <David.Francis@amd.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 127 ++++++++++++++++++++++++++
 include/drm/drm_dp_mst_helper.h       |   2 +
 2 files changed, 129 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index ae2f986d76a2..dd2ca065cc92 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -4147,3 +4147,130 @@ static void drm_dp_mst_unregister_i2c_bus(struct drm_dp_aux *aux)
 {
 	i2c_del_adapter(&aux->ddc);
 }
+
+/**
+ * drm_dp_mst_is_virtual_dpcd() - Is the given port a virtual DP Peer Device
+ * @port: The port to check
+ *
+ * A single physical MST hub object can be represented in the topology
+ * by multiple branches, with virtual ports between those branches.
+ *
+ * As of DP1.4, An MST hub with internal (virtual) ports must expose
+ * certain DPCD registers over those ports. See sections 2.6.1.1.1
+ * and 2.6.1.1.2 of Display Port specification v1.4 for details.
+ *
+ * May acquire mgr->lock
+ *
+ * Returns:
+ * true if the port is a virtual DP peer device, false otherwise
+ */
+static bool drm_dp_mst_is_virtual_dpcd(struct drm_dp_mst_port *port)
+{
+	struct drm_dp_mst_port *downstream_port;
+
+	if (!port || port->dpcd_rev < DP_DPCD_REV_14)
+		return false;
+
+	/* Virtual DP Sink (Internal Display Panel) */
+	if (port->port_num >= 8)
+		return true;
+
+	/* DP-to-HDMI Protocol Converter */
+	if (port->pdt == DP_PEER_DEVICE_DP_LEGACY_CONV &&
+	    !port->mcs &&
+	    port->ldps)
+		return true;
+
+	/* DP-to-DP */
+	mutex_lock(&port->mgr->lock);
+	if (port->pdt == DP_PEER_DEVICE_MST_BRANCHING &&
+	    port->mstb &&
+	    port->mstb->num_ports == 2) {
+		list_for_each_entry(downstream_port, &port->mstb->ports, next) {
+			if (downstream_port->pdt == DP_PEER_DEVICE_SST_SINK &&
+			    !downstream_port->input) {
+				mutex_unlock(&port->mgr->lock);
+				return true;
+			}
+		}
+	}
+	mutex_unlock(&port->mgr->lock);
+
+	return false;
+}
+
+/**
+ * drm_dp_mst_dsc_aux_for_port() - Find the correct aux for DSC
+ * @port: The port to check. A leaf of the MST tree with an attached display.
+ *
+ * Depending on the situation, DSC may be enabled via the endpoint aux,
+ * the immediately upstream aux, or the connector's physical aux.
+ *
+ * This is both the correct aux to read DSC_CAPABILITY and the
+ * correct aux to write DSC_ENABLED.
+ *
+ * This operation can be expensive (up to four aux reads), so
+ * the caller should cache the return.
+ *
+ * Returns:
+ * NULL if DSC cannot be enabled on this port, otherwise the aux device
+ */
+struct drm_dp_aux *drm_dp_mst_dsc_aux_for_port(struct drm_dp_mst_port *port)
+{
+	struct drm_dp_mst_port *immediate_upstream_port;
+	struct drm_dp_mst_port *fec_port;
+
+	if (!port)
+		return NULL;
+
+	if (port->parent)
+		immediate_upstream_port = port->parent->port_parent;
+	else
+		immediate_upstream_port = NULL;
+
+	fec_port = immediate_upstream_port;
+	while (fec_port) {
+		/*
+		 * Each physical link (i.e. not a virtual port) between the
+		 * output and the primary device must support FEC
+		 */
+		if (!drm_dp_mst_is_virtual_dpcd(fec_port) &&
+		    !fec_port->fec_capable)
+			return NULL;
+
+		fec_port = fec_port->parent->port_parent;
+	}
+
+	/* DP-to-DP peer device */
+	if (drm_dp_mst_is_virtual_dpcd(immediate_upstream_port)) {
+		u8 upstream_dsc;
+		u8 endpoint_dsc;
+		u8 endpoint_fec;
+
+		if (drm_dp_dpcd_read(&port->aux,
+				     DP_DSC_SUPPORT, &endpoint_dsc, 1) < 0)
+			return NULL;
+		if (drm_dp_dpcd_read(&port->aux,
+				     DP_FEC_CAPABILITY, &endpoint_fec, 1) < 0)
+			return NULL;
+		if (drm_dp_dpcd_read(&immediate_upstream_port->aux,
+				     DP_DSC_SUPPORT, &upstream_dsc, 1) < 0)
+			return NULL;
+
+		/* Enpoint decompression with DP-to-DP peer device */
+		if ((endpoint_dsc & DP_DSC_DECOMPRESSION_IS_SUPPORTED) &&
+		    (endpoint_fec & DP_FEC_CAPABLE) &&
+		    (upstream_dsc & 0x2) /* DSC passthrough */)
+			return &port->aux;
+
+		/* Virtual DPCD decompression with DP-to-DP peer device */
+		return &immediate_upstream_port->aux;
+	}
+
+	/* Virtual DPCD decompression with DP-to-HDMI or Virtual DP Sink */
+	if (drm_dp_mst_is_virtual_dpcd(port))
+		return &port->aux;
+
+	return NULL;
+}
+EXPORT_SYMBOL(drm_dp_mst_dsc_aux_for_port);
diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
index f113ae04fa88..4cf738545dfb 100644
--- a/include/drm/drm_dp_mst_helper.h
+++ b/include/drm/drm_dp_mst_helper.h
@@ -673,6 +673,8 @@ int __must_check drm_dp_mst_atomic_check(struct drm_atomic_state *state);
 void drm_dp_mst_get_port_malloc(struct drm_dp_mst_port *port);
 void drm_dp_mst_put_port_malloc(struct drm_dp_mst_port *port);
 
+struct drm_dp_aux *drm_dp_mst_dsc_aux_for_port(struct drm_dp_mst_port *port);
+
 extern const struct drm_private_state_funcs drm_dp_mst_topology_state_funcs;
 
 /**
-- 
2.17.1

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Re: [PATCH 08/15] drm/dp_mst: Add helpers for MST DSC and virtual DPCD aux

[Lyude Paul]

Reviewed-by: Lyude Paul <lyude@redhat.com>

On Wed, 2019-09-18 at 16:26 -0400, mikita.lipski@amd.com wrote:
> From: David Francis <David.Francis@amd.com>
> 
> Add drm_dp_mst_dsc_aux_for_port. To enable DSC, the DSC_ENABLED
> register might have to be written on the leaf port's DPCD,
> its parent's DPCD, or the MST manager's DPCD. This function
> finds the correct aux for the job.
> 
> As part of this, add drm_dp_mst_is_virtual_dpcd. Virtual DPCD
> is a DP feature new in DP v1.4, which exposes certain DPCD
> registers on virtual ports.
> 
> v2: Remember to unlock mutex on all paths
> v3: Refactor to match coding style and increase brevity
> 
> Cc: Lyude Paul <lyude@redhat.com>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Harry Wentland <harry.wentland@amd.com>
> Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com>
> Signed-off-by: David Francis <David.Francis@amd.com>
> ---
>  drivers/gpu/drm/drm_dp_mst_topology.c | 127 ++++++++++++++++++++++++++
>  include/drm/drm_dp_mst_helper.h       |   2 +
>  2 files changed, 129 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c
> b/drivers/gpu/drm/drm_dp_mst_topology.c
> index ae2f986d76a2..dd2ca065cc92 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -4147,3 +4147,130 @@ static void drm_dp_mst_unregister_i2c_bus(struct
> drm_dp_aux *aux)
>  {
>  	i2c_del_adapter(&aux->ddc);
>  }
> +
> +/**
> + * drm_dp_mst_is_virtual_dpcd() - Is the given port a virtual DP Peer
> Device
> + * @port: The port to check
> + *
> + * A single physical MST hub object can be represented in the topology
> + * by multiple branches, with virtual ports between those branches.
> + *
> + * As of DP1.4, An MST hub with internal (virtual) ports must expose
> + * certain DPCD registers over those ports. See sections 2.6.1.1.1
> + * and 2.6.1.1.2 of Display Port specification v1.4 for details.
> + *
> + * May acquire mgr->lock
> + *
> + * Returns:
> + * true if the port is a virtual DP peer device, false otherwise
> + */
> +static bool drm_dp_mst_is_virtual_dpcd(struct drm_dp_mst_port *port)
> +{
> +	struct drm_dp_mst_port *downstream_port;
> +
> +	if (!port || port->dpcd_rev < DP_DPCD_REV_14)
> +		return false;
> +
> +	/* Virtual DP Sink (Internal Display Panel) */
> +	if (port->port_num >= 8)
> +		return true;
> +
> +	/* DP-to-HDMI Protocol Converter */
> +	if (port->pdt == DP_PEER_DEVICE_DP_LEGACY_CONV &&
> +	    !port->mcs &&
> +	    port->ldps)
> +		return true;
> +
> +	/* DP-to-DP */
> +	mutex_lock(&port->mgr->lock);
> +	if (port->pdt == DP_PEER_DEVICE_MST_BRANCHING &&
> +	    port->mstb &&
> +	    port->mstb->num_ports == 2) {
> +		list_for_each_entry(downstream_port, &port->mstb->ports, next)
> {
> +			if (downstream_port->pdt == DP_PEER_DEVICE_SST_SINK &&
> +			    !downstream_port->input) {
> +				mutex_unlock(&port->mgr->lock);
> +				return true;
> +			}
> +		}
> +	}
> +	mutex_unlock(&port->mgr->lock);
> +
> +	return false;
> +}
> +
> +/**
> + * drm_dp_mst_dsc_aux_for_port() - Find the correct aux for DSC
> + * @port: The port to check. A leaf of the MST tree with an attached
> display.
> + *
> + * Depending on the situation, DSC may be enabled via the endpoint aux,
> + * the immediately upstream aux, or the connector's physical aux.
> + *
> + * This is both the correct aux to read DSC_CAPABILITY and the
> + * correct aux to write DSC_ENABLED.
> + *
> + * This operation can be expensive (up to four aux reads), so
> + * the caller should cache the return.
> + *
> + * Returns:
> + * NULL if DSC cannot be enabled on this port, otherwise the aux device
> + */
> +struct drm_dp_aux *drm_dp_mst_dsc_aux_for_port(struct drm_dp_mst_port
> *port)
> +{
> +	struct drm_dp_mst_port *immediate_upstream_port;
> +	struct drm_dp_mst_port *fec_port;
> +
> +	if (!port)
> +		return NULL;
> +
> +	if (port->parent)
> +		immediate_upstream_port = port->parent->port_parent;
> +	else
> +		immediate_upstream_port = NULL;
> +
> +	fec_port = immediate_upstream_port;
> +	while (fec_port) {
> +		/*
> +		 * Each physical link (i.e. not a virtual port) between the
> +		 * output and the primary device must support FEC
> +		 */
> +		if (!drm_dp_mst_is_virtual_dpcd(fec_port) &&
> +		    !fec_port->fec_capable)
> +			return NULL;
> +
> +		fec_port = fec_port->parent->port_parent;
> +	}
> +
> +	/* DP-to-DP peer device */
> +	if (drm_dp_mst_is_virtual_dpcd(immediate_upstream_port)) {
> +		u8 upstream_dsc;
> +		u8 endpoint_dsc;
> +		u8 endpoint_fec;
> +
> +		if (drm_dp_dpcd_read(&port->aux,
> +				     DP_DSC_SUPPORT, &endpoint_dsc, 1) < 0)
> +			return NULL;
> +		if (drm_dp_dpcd_read(&port->aux,
> +				     DP_FEC_CAPABILITY, &endpoint_fec, 1) < 0)
> +			return NULL;
> +		if (drm_dp_dpcd_read(&immediate_upstream_port->aux,
> +				     DP_DSC_SUPPORT, &upstream_dsc, 1) < 0)
> +			return NULL;
> +
> +		/* Enpoint decompression with DP-to-DP peer device */
> +		if ((endpoint_dsc & DP_DSC_DECOMPRESSION_IS_SUPPORTED) &&
> +		    (endpoint_fec & DP_FEC_CAPABLE) &&
> +		    (upstream_dsc & 0x2) /* DSC passthrough */)
> +			return &port->aux;
> +
> +		/* Virtual DPCD decompression with DP-to-DP peer device */
> +		return &immediate_upstream_port->aux;
> +	}
> +
> +	/* Virtual DPCD decompression with DP-to-HDMI or Virtual DP Sink */
> +	if (drm_dp_mst_is_virtual_dpcd(port))
> +		return &port->aux;
> +
> +	return NULL;
> +}
> +EXPORT_SYMBOL(drm_dp_mst_dsc_aux_for_port);
> diff --git a/include/drm/drm_dp_mst_helper.h
> b/include/drm/drm_dp_mst_helper.h
> index f113ae04fa88..4cf738545dfb 100644
> --- a/include/drm/drm_dp_mst_helper.h
> +++ b/include/drm/drm_dp_mst_helper.h
> @@ -673,6 +673,8 @@ int __must_check drm_dp_mst_atomic_check(struct
> drm_atomic_state *state);
>  void drm_dp_mst_get_port_malloc(struct drm_dp_mst_port *port);
>  void drm_dp_mst_put_port_malloc(struct drm_dp_mst_port *port);
>  
> +struct drm_dp_aux *drm_dp_mst_dsc_aux_for_port(struct drm_dp_mst_port
> *port);
> +
>  extern const struct drm_private_state_funcs
> drm_dp_mst_topology_state_funcs;
>  
>  /**
-- 
Cheers,
	Lyude Paul

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[PATCH 10/15] drm/amd/display: Use correct helpers to compute timeslots

[mikita.lipski]

From: David Francis <David.Francis@amd.com>

We were using drm helpers to convert a timing into its
bandwidth, its bandwidth into pbn, and its pbn into timeslots

These helpers
-Did not take DSC timings into account
-Used the link rate and lane count of the link's aux device,
which are not the same as the link's current cap
-Did not take FEC into account (FEC reduces the PBN per timeslot)

For converting timing into PBN, use the new function
drm_dp_calc_pbn_mode_dsc that handles the DSC case

For converting PBN into time slots, amdgpu doesn't use the
'correct' atomic method (drm_dp_atomic_find_vcpi_slots), so
don't add a new helper to cover our approach. Use the same
means of calculating pbn per time slot as the DSC code.

Cc: Jerry Zuo <Jerry.Zuo@amd.com>
Cc: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: David Francis <David.Francis@amd.com>
---
 .../amd/display/amdgpu_dm/amdgpu_dm_helpers.c  | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
index b151a5a51a94..aaf3158534ab 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
@@ -188,8 +188,8 @@ bool dm_helpers_dp_mst_write_payload_allocation_table(
 	int slots = 0;
 	bool ret;
 	int clock;
-	int bpp = 0;
 	int pbn = 0;
+	int pbn_per_timeslot, bpp = 0;
 
 	aconnector = (struct amdgpu_dm_connector *)stream->dm_stream_context;
 
@@ -233,11 +233,19 @@ bool dm_helpers_dp_mst_write_payload_allocation_table(
 
 		bpp = bpp * 3;
 
-		/* TODO need to know link rate */
-
-		pbn = drm_dp_calc_pbn_mode(clock, bpp, false);
+#ifdef CONFIG_DRM_AMD_DC_DSC_SUPPORT
+		if (stream->timing.flags.DSC)
+			pbn = drm_dp_calc_pbn_mode(clock,
+						   stream->timing.dsc_cfg.bits_per_pixel,
+						   true);
+		else
+#endif
+			pbn = drm_dp_calc_pbn_mode(clock, bpp, false);
 
-		slots = drm_dp_find_vcpi_slots(mst_mgr, pbn);
+		/* Convert kilobits per second / 64 (for 64 timeslots) to pbn (54/64 megabytes per second) */
+		pbn_per_timeslot = dc_link_bandwidth_kbps(
+				stream->link, dc_link_get_link_cap(stream->link)) / (8 * 1000 * 54);
+		slots = DIV_ROUND_UP(pbn, pbn_per_timeslot);
 		ret = drm_dp_mst_allocate_vcpi(mst_mgr, mst_port, pbn, slots);
 
 		if (!ret)
-- 
2.17.1

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[PATCH 12/15] drm/amd/display: Validate DSC caps on MST endpoints

[mikita.lipski]

From: David Francis <David.Francis@amd.com>

During MST mode enumeration, if a new dc_sink is created,
populate it with dsc caps as appropriate.

Use drm_dp_mst_dsc_aux_for_port to get the raw caps,
then parse them onto dc_sink with dc_dsc_parse_dsc_dpcd.

Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com>
Signed-off-by: David Francis <David.Francis@amd.com>
---
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h |  3 ++
 .../display/amdgpu_dm/amdgpu_dm_mst_types.c   | 31 ++++++++++++++++++-
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
index c36fe617eac4..1228449bca84 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
@@ -268,6 +268,9 @@ struct amdgpu_dm_connector {
 	struct drm_dp_mst_port *port;
 	struct amdgpu_dm_connector *mst_port;
 	struct amdgpu_encoder *mst_encoder;
+#ifdef CONFIG_DRM_AMD_DC_DSC_SUPPORT
+	struct drm_dp_aux *dsc_aux;
+#endif
 
 	/* TODO see if we can merge with ddc_bus or make a dm_connector */
 	struct amdgpu_i2c_adapter *i2c;
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
index 4e1bbf5bbe77..379bc5f388f7 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
@@ -25,6 +25,7 @@
 
 #include <linux/version.h>
 #include <drm/drm_atomic_helper.h>
+#include <drm/drm_dp_mst_helper.h>
 #include "dm_services.h"
 #include "amdgpu.h"
 #include "amdgpu_dm.h"
@@ -189,6 +190,28 @@ static const struct drm_connector_funcs dm_dp_mst_connector_funcs = {
 	.early_unregister = amdgpu_dm_mst_connector_early_unregister,
 };
 
+#ifdef CONFIG_DRM_AMD_DC_DSC_SUPPORT
+static bool validate_dsc_caps_on_connector(struct amdgpu_dm_connector *aconnector)
+{
+	struct dc_sink *dc_sink = aconnector->dc_sink;
+	struct drm_dp_mst_port *port = aconnector->port;
+	u8 dsc_caps[16] = { 0 };
+
+	aconnector->dsc_aux = drm_dp_mst_dsc_aux_for_port(port);
+
+	if (!aconnector->dsc_aux)
+		return false;
+
+	if (drm_dp_dpcd_read(aconnector->dsc_aux, DP_DSC_SUPPORT, dsc_caps, 16) < 0)
+		return false;
+
+	if (!dc_dsc_parse_dsc_dpcd(dsc_caps, NULL, &dc_sink->sink_dsc_caps.dsc_dec_caps))
+		return false;
+
+	return true;
+}
+#endif
+
 static int dm_dp_mst_get_modes(struct drm_connector *connector)
 {
 	struct amdgpu_dm_connector *aconnector = to_amdgpu_dm_connector(connector);
@@ -231,10 +254,16 @@ static int dm_dp_mst_get_modes(struct drm_connector *connector)
 		/* dc_link_add_remote_sink returns a new reference */
 		aconnector->dc_sink = dc_sink;
 
-		if (aconnector->dc_sink)
+		if (aconnector->dc_sink) {
 			amdgpu_dm_update_freesync_caps(
 					connector, aconnector->edid);
 
+#ifdef CONFIG_DRM_AMD_DC_DSC_SUPPORT
+			if (!validate_dsc_caps_on_connector(aconnector))
+				memset(&aconnector->dc_sink->sink_dsc_caps,
+				       0, sizeof(aconnector->dc_sink->sink_dsc_caps));
+#endif
+		}
 	}
 
 	drm_connector_update_edid_property(
-- 
2.17.1

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[PATCH 01/15] drm/amdgpu: Add encoder atomic check

[mikita.lipski-5C7GfCeVMHo]

From: Mikita Lipski <mikita.lipski@amd.com>

[why]
In order to comply with new MST atomic check
we have to find and add VCPI slots to the state
during atomic check whenever their is a change on
mode or connector.
[how]
- Verify that it is a MST connection
- Convert new stream's clock and bpp
- Calculate PBN based on stream parameters
- Find and add VCPI slots to the state

Cc: Lyude Paul <lyude@redhat.com>
Signed-off-by: Mikita Lipski <mikita.lipski@amd.com>
---
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 59 +++++++++++++++++++
 1 file changed, 59 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 7b0ca2e1ed8b..d700b962d338 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -4432,6 +4432,65 @@ static int dm_encoder_helper_atomic_check(struct drm_encoder *encoder,
 					  struct drm_crtc_state *crtc_state,
 					  struct drm_connector_state *conn_state)
 {
+	struct drm_atomic_state *state = crtc_state->state;
+	struct drm_connector *connector = conn_state->connector;
+	struct amdgpu_dm_connector *aconnector = to_amdgpu_dm_connector(connector);
+	struct dm_crtc_state *dm_new_crtc_state = to_dm_crtc_state(crtc_state);
+	const struct drm_display_mode *adjusted_mode = &crtc_state->adjusted_mode;
+	struct drm_dp_mst_topology_mgr *mst_mgr;
+	struct drm_dp_mst_port *mst_port;
+	int pbn, slots,clock, bpp = 0;
+
+	if (!dm_new_crtc_state)
+		return 0;
+
+	if (!aconnector || !aconnector->port)
+		return 0;
+
+	mst_port = aconnector->port;
+	mst_mgr = &aconnector->mst_port->mst_mgr;
+
+	if (!mst_mgr->mst_state)
+		return 0;
+
+	if (!crtc_state->connectors_changed && !crtc_state->mode_changed)
+		return 0;
+
+	switch (convert_color_depth_from_display_info(connector, conn_state)) {
+	case COLOR_DEPTH_666:
+		bpp = 6;
+		break;
+	case COLOR_DEPTH_888:
+		bpp = 8;
+		break;
+	case COLOR_DEPTH_101010:
+		bpp = 10;
+		break;
+	case COLOR_DEPTH_121212:
+		bpp = 12;
+		break;
+	case COLOR_DEPTH_141414:
+		bpp = 14;
+		break;
+	case COLOR_DEPTH_161616:
+		bpp = 16;
+		break;
+	default:
+		ASSERT(bpp != 0);
+		break;
+	}
+
+	bpp *= 3;
+	clock = adjusted_mode->clock;
+	pbn = drm_dp_calc_pbn_mode(clock, bpp);
+	slots = drm_dp_atomic_find_vcpi_slots(state,
+						mst_mgr,
+						mst_port,
+						pbn);
+	if (slots < 0) {
+		DRM_DEBUG_KMS("failed finding vcpi slots:%d\n", slots);
+		return slots;
+	}
 	return 0;
 }
 
-- 
2.17.1

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Re: [PATCH 01/15] drm/amdgpu: Add encoder atomic check

[Lyude Paul]

Haven't looked at these quite yet, but I just wanted to say ahead of time that
from a quick glance these look like a big step in the right direction :).
Awesome work!

I will review this ASAP 

On Wed, 2019-09-18 at 16:26 -0400, mikita.lipski@amd.com wrote:
> From: Mikita Lipski <mikita.lipski@amd.com>
> 
> [why]
> In order to comply with new MST atomic check
> we have to find and add VCPI slots to the state
> during atomic check whenever their is a change on
> mode or connector.
> [how]
> - Verify that it is a MST connection
> - Convert new stream's clock and bpp
> - Calculate PBN based on stream parameters
> - Find and add VCPI slots to the state
> 
> Cc: Lyude Paul <lyude@redhat.com>
> Signed-off-by: Mikita Lipski <mikita.lipski@amd.com>
> ---
>  .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 59 +++++++++++++++++++
>  1 file changed, 59 insertions(+)
> 
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index 7b0ca2e1ed8b..d700b962d338 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -4432,6 +4432,65 @@ static int dm_encoder_helper_atomic_check(struct
> drm_encoder *encoder,
>  					  struct drm_crtc_state *crtc_state,
>  					  struct drm_connector_state
> *conn_state)
>  {
> +	struct drm_atomic_state *state = crtc_state->state;
> +	struct drm_connector *connector = conn_state->connector;
> +	struct amdgpu_dm_connector *aconnector =
> to_amdgpu_dm_connector(connector);
> +	struct dm_crtc_state *dm_new_crtc_state =
> to_dm_crtc_state(crtc_state);
> +	const struct drm_display_mode *adjusted_mode = &crtc_state-
> >adjusted_mode;
> +	struct drm_dp_mst_topology_mgr *mst_mgr;
> +	struct drm_dp_mst_port *mst_port;
> +	int pbn, slots,clock, bpp = 0;
> +
> +	if (!dm_new_crtc_state)
> +		return 0;
> +
> +	if (!aconnector || !aconnector->port)
> +		return 0;
> +
> +	mst_port = aconnector->port;
> +	mst_mgr = &aconnector->mst_port->mst_mgr;
> +
> +	if (!mst_mgr->mst_state)
> +		return 0;
> +
> +	if (!crtc_state->connectors_changed && !crtc_state->mode_changed)
> +		return 0;
> +
> +	switch (convert_color_depth_from_display_info(connector, conn_state))
> {
> +	case COLOR_DEPTH_666:
> +		bpp = 6;
> +		break;
> +	case COLOR_DEPTH_888:
> +		bpp = 8;
> +		break;
> +	case COLOR_DEPTH_101010:
> +		bpp = 10;
> +		break;
> +	case COLOR_DEPTH_121212:
> +		bpp = 12;
> +		break;
> +	case COLOR_DEPTH_141414:
> +		bpp = 14;
> +		break;
> +	case COLOR_DEPTH_161616:
> +		bpp = 16;
> +		break;
> +	default:
> +		ASSERT(bpp != 0);
> +		break;
> +	}
> +
> +	bpp *= 3;
> +	clock = adjusted_mode->clock;
> +	pbn = drm_dp_calc_pbn_mode(clock, bpp);
> +	slots = drm_dp_atomic_find_vcpi_slots(state,
> +						mst_mgr,
> +						mst_port,
> +						pbn);
> +	if (slots < 0) {
> +		DRM_DEBUG_KMS("failed finding vcpi slots:%d\n", slots);
> +		return slots;
> +	}
>  	return 0;
>  }
>  
-- 
Cheers,
	Lyude Paul

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Re: [PATCH 01/15] drm/amdgpu: Add encoder atomic check

[Lyude Paul]

Ok, so reviewing this is kind of difficult because this series doesn't apply
to drm-tip, and also doesn't make any mention of what branch it's supposed to
apply to. So there's no way for me to apply any of these changes in my tree to
get an idea of how things look overall with these patches applied. Could you
please base the next series on top of drm-tip?

In the mean time, I've left as much feedback as I can below:


For starters, this patch should be combined with the next patch in the series
since you really can't use drm_dp_atomic_find_vcpi_slots() without using
drm_dp_atomic_release_vcpi_slots(). More down below

On Wed, 2019-09-18 at 16:26 -0400, mikita.lipski@amd.com wrote:
> From: Mikita Lipski <mikita.lipski@amd.com>
> 
> [why]
> In order to comply with new MST atomic check
> we have to find and add VCPI slots to the state
> during atomic check whenever their is a change on
> mode or connector.
> [how]
> - Verify that it is a MST connection
> - Convert new stream's clock and bpp
> - Calculate PBN based on stream parameters
> - Find and add VCPI slots to the state
> 
> Cc: Lyude Paul <lyude@redhat.com>
> Signed-off-by: Mikita Lipski <mikita.lipski@amd.com>
> ---
>  .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 59 +++++++++++++++++++
>  1 file changed, 59 insertions(+)
> 
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index 7b0ca2e1ed8b..d700b962d338 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -4432,6 +4432,65 @@ static int dm_encoder_helper_atomic_check(struct
> drm_encoder *encoder,
>  					  struct drm_crtc_state *crtc_state,
>  					  struct drm_connector_state
> *conn_state)
>  {
> +	struct drm_atomic_state *state = crtc_state->state;
> +	struct drm_connector *connector = conn_state->connector;
> +	struct amdgpu_dm_connector *aconnector =
> to_amdgpu_dm_connector(connector);
> +	struct dm_crtc_state *dm_new_crtc_state =
> to_dm_crtc_state(crtc_state);
> +	const struct drm_display_mode *adjusted_mode = &crtc_state-
> >adjusted_mode;
> +	struct drm_dp_mst_topology_mgr *mst_mgr;
> +	struct drm_dp_mst_port *mst_port;
> +	int pbn, slots,clock, bpp = 0;
> +
> +	if (!dm_new_crtc_state)
> +		return 0;
> +
> +	if (!aconnector || !aconnector->port)
> +		return 0;

...in what situation would aconnector ever be NULL? Same for aconnector->port, 
the drm_dp_mst_port stays around until the drm_connector is destroyed.
> +
> +	mst_port = aconnector->port;
> +	mst_mgr = &aconnector->mst_port->mst_mgr;
> +
> +	if (!mst_mgr->mst_state)
> +		return 0;

I'm confused here, what is the purpose of this check? mst_mgr->mst_state
shouldn't be touched directly ever, as it refers to the currently committed
mgr state. the way to retrieve the mgr's atomic state is:

https://01.org/linuxgraphics/gfx-docs/drm/gpu/drm-kms-helpers.html#c.drm_atomic_get_mst_topology_state

Even then though, there's no actual need to grab the mst_state here manually.
drm_dp_atomic_find_vcpi_slots() does this for you

> +
> +	if (!crtc_state->connectors_changed && !crtc_state->mode_changed)
> +		return 0;
> +
> +	switch (convert_color_depth_from_display_info(connector, conn_state))
> {
> +	case COLOR_DEPTH_666:
> +		bpp = 6;
> +		break;
> +	case COLOR_DEPTH_888:
> +		bpp = 8;
> +		break;
> +	case COLOR_DEPTH_101010:
> +		bpp = 10;
> +		break;
> +	case COLOR_DEPTH_121212:
> +		bpp = 12;
> +		break;
> +	case COLOR_DEPTH_141414:
> +		bpp = 14;
> +		break;
> +	case COLOR_DEPTH_161616:
> +		bpp = 16;
> +		break;
> +	default:
> +		ASSERT(bpp != 0);
> +		break;
> +	}
> +
> +	bpp *= 3;
> +	clock = adjusted_mode->clock;
> +	pbn = drm_dp_calc_pbn_mode(clock, bpp);

I might have forgotten to mention this in the documentation (I'll double check
after sending this out and fix it if I did...), but it's a good idea to only
recalculate the PBN when !drm_atomic_state->duplicated. The reason for this is
that when we're resuming the system from S3, there's a chance that MST
topologies which were previously connected to the system might no longer be
present or may have changed.

When resuming from S3, or any other situation where the GPU needs to save and
restore it's atomic state, the general expectation is that the state that was
saved is basically identical to the state that was resumed since a different
state won't have the guarantee of passing the atomic check. An example
scenario (note that we don't reprobe topologies after resume yet, but we will
be doing this very soon):

 * MST connector DP-4 starts off with a bpp of 8
 * The GPU has a VCPI table that is currently full, and includes an active
   allocation for DP-4.
 * The system goes into S3, and the GPU is suspended and the atomic state
   saved (this sets state->duplicated to true)
 * While the system is still in S3, the user plugs in a monitor that is
   identical, except for the fact it has 16bpp
 * The system resumes, and the GPU begins resuming. amdgpu goes to restore the
   atomic state from before entering S3
 * Because DP-4 now has a bpp of 16, we use that instead of the previous 8bpp
   from before and end up with a VCPI allocation that is twice as large as
   before
 * The new twice-as-large VCPI allocation does not fit along with the rest of
   the allocations, and causes the atomic_check during resume to fail (note
   that during resume, it's expected that the driver does whatever it takes to
   make the atomic_check pass)

Copying the PBN value as-is from the duplicated atomic state when state-
>duplicated == true instead of recalculating it allows us to avoid this by
making sure that regardless of changes with the connector, we still end up
restoring the same VCPI allocations that we had before.

Note-this does potentially leave us with the possibility that we could in
fact, resume and end up restoring an atomic state with an incorrect VCPI
table. I don't think we've really figured out any way around this, and with
suspend/resume it's expected that the driver is able to cope with breakages
like this until another atomic modeset happens to correct things. So for now,
that's OK.

I'd really recommend looking at nouveau's implementation of this as an
example, specifically nv50_msto_atomic_check().

> +	slots = drm_dp_atomic_find_vcpi_slots(state,
> +						mst_mgr,
> +						mst_port,
> +						pbn);
> +	if (slots < 0) {
> +		DRM_DEBUG_KMS("failed finding vcpi slots:%d\n", slots);

I think you meant DRM_DEBUG_ATOMIC() here

Also, this is still a big step in the right direction but there's a bit more
missing here. This code only checks if slots != 0 and then drops the value.
Later, dm_helpers_dp_mst_write_payload_allocation_table() calculates the VCPI
allocation that actually gets used in the commit in the atomic commit using
the deprecated drm_dp_find_vcpi_slots() helper.

What we want here instead is to just drop the usage of
drm_dp_find_vcpi_slots() entirely, store the VCPI slot allocation returned by
drm_dp_atomic_find_vcpi_slots() in the driver's atomic state, then use that
value when performing the actual VCPI allocation in
dm_helpers_dp_mst_write_payload_allocation_table() using
drm_dp_mst_allocate_vcpi(). Maybe struct dc_stream_state is a good place to
add this? (feel free to store the pbn as well there, to save a redundant
drm_dp_calc_pbn_mode() call).

> +		return slots;
> +	}
>  	return 0;
>  }
>  
-- 
Cheers,
	Lyude Paul

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[PATCH 03/15] drm/amdgpu: validate mst topology in atomic check

[mikita.lipski-5C7GfCeVMHo]

From: Mikita Lipski <mikita.lipski@amd.com>

[why]
Validate mst topology and the number of VCPI slots available
for a new state. Fail if topology has no more bandwidth for
a new state.
[how]
Pass the atomic state to drm_dp_mst_atomic_check to verify
if the new topology is possible.

Cc: Lyude Paul <lyude@redhat.com>
Signed-off-by: Mikita Lipski <mikita.lipski@amd.com>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index d700b962d338..39c239a08633 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -7485,6 +7485,11 @@ static int amdgpu_dm_atomic_check(struct drm_device *dev,
 	if (ret)
 		goto fail;
 
+	/* Perform validation of MST topology in the state*/
+	ret = drm_dp_mst_atomic_check(state);
+	if (ret)
+		goto fail;
+
 	if (state->legacy_cursor_update) {
 		/*
 		 * This is a fast cursor update coming from the plane update
-- 
2.17.1

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Re: [PATCH 03/15] drm/amdgpu: validate mst topology in atomic check

[Lyude Paul]

This also needs to be squashed into the previous two patches. There's no point
in using drm_dp_atomic_find_vcpi_slots() or drm_dp_atomic_release_vcpi_slots()
without drm_dp_mst_atomic_check(), since the VCPI allocations setup by the two
functions aren't validated until then.

On Wed, 2019-09-18 at 16:26 -0400, mikita.lipski@amd.com wrote:
> From: Mikita Lipski <mikita.lipski@amd.com>
> 
> [why]
> Validate mst topology and the number of VCPI slots available
> for a new state. Fail if topology has no more bandwidth for
> a new state.
> [how]
> Pass the atomic state to drm_dp_mst_atomic_check to verify
> if the new topology is possible.
> 
> Cc: Lyude Paul <lyude@redhat.com>
> Signed-off-by: Mikita Lipski <mikita.lipski@amd.com>
> ---
>  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index d700b962d338..39c239a08633 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -7485,6 +7485,11 @@ static int amdgpu_dm_atomic_check(struct drm_device
> *dev,
>  	if (ret)
>  		goto fail;
>  
> +	/* Perform validation of MST topology in the state*/
> +	ret = drm_dp_mst_atomic_check(state);
> +	if (ret)
> +		goto fail;
> +
>  	if (state->legacy_cursor_update) {
>  		/*
>  		 * This is a fast cursor update coming from the plane update
-- 
Cheers,
	Lyude Paul

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[PATCH 04/15] drm/dp_mst: Add PBN calculation for DSC modes

[mikita.lipski-5C7GfCeVMHo]

From: David Francis <David.Francis@amd.com>

With DSC, bpp can be fractional in multiples of 1/16.

Change drm_dp_calc_pbn_mode to reflect this, adding a new
parameter bool dsc. When this parameter is true, treat the
bpp parameter as having units not of bits per pixel, but
1/16 of a bit per pixel

v2: Don't add separate function for this

Change-Id: I33ef6f53c44dc32aa869aa9741ba0339aaf5e54f
Cc: amd-gfx@lists.freedesktop.org
Cc: nouveau@lists.freedesktop.org
Cc: intel-gfx@lists.freedesktop.org
Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: David Francis <David.Francis@amd.com>
Signed-off-by: Mikita Lipski <mikita.lipski@amd.com>
---
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c    |  8 +++++++-
 .../amd/display/amdgpu_dm/amdgpu_dm_helpers.c    |  2 +-
 drivers/gpu/drm/drm_dp_mst_topology.c            | 16 ++++++++++++----
 drivers/gpu/drm/i915/intel_dp_mst.c              |  3 ++-
 drivers/gpu/drm/nouveau/dispnv50/disp.c          |  3 ++-
 drivers/gpu/drm/radeon/radeon_dp_mst.c           |  2 +-
 include/drm/drm_dp_mst_helper.h                  |  3 +--
 7 files changed, 26 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 39c239a08633..1130298c6930 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -4482,7 +4482,13 @@ static int dm_encoder_helper_atomic_check(struct drm_encoder *encoder,
 
 	bpp *= 3;
 	clock = adjusted_mode->clock;
-	pbn = drm_dp_calc_pbn_mode(clock, bpp);
+#ifdef CONFIG_DRM_AMD_DC_DSC_SUPPORT
+	if (aconnector->dc_sink &&
+	    aconnector->dc_sink->sink_dsc_caps.dsc_dec_caps.is_dsc_supported)
+		pbn = drm_dp_calc_pbn_mode(clock, bpp, true);
+	else
+#endif
+		pbn = drm_dp_calc_pbn_mode(clock, bpp, false);
 	slots = drm_dp_atomic_find_vcpi_slots(state,
 						mst_mgr,
 						mst_port,
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
index 555af4a8c0ef..b151a5a51a94 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
@@ -235,7 +235,7 @@ bool dm_helpers_dp_mst_write_payload_allocation_table(
 
 		/* TODO need to know link rate */
 
-		pbn = drm_dp_calc_pbn_mode(clock, bpp);
+		pbn = drm_dp_calc_pbn_mode(clock, bpp, false);
 
 		slots = drm_dp_find_vcpi_slots(mst_mgr, pbn);
 		ret = drm_dp_mst_allocate_vcpi(mst_mgr, mst_port, pbn, slots);
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 398e7314ea8b..659099366f8b 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -3531,10 +3531,11 @@ EXPORT_SYMBOL(drm_dp_check_act_status);
  * drm_dp_calc_pbn_mode() - Calculate the PBN for a mode.
  * @clock: dot clock for the mode
  * @bpp: bpp for the mode.
+ * @dsc: DSC mode. If true, bpp has units of 1/16 of a bit per pixel
  *
  * This uses the formula in the spec to calculate the PBN value for a mode.
  */
-int drm_dp_calc_pbn_mode(int clock, int bpp)
+int drm_dp_calc_pbn_mode(int clock, int bpp, bool dsc)
 {
 	u64 kbps;
 	s64 peak_kbps;
@@ -3552,11 +3553,18 @@ int drm_dp_calc_pbn_mode(int clock, int bpp)
 	 * peak_kbps *= (1006/1000)
 	 * peak_kbps *= (64/54)
 	 * peak_kbps *= 8    convert to bytes
+	 *
+	 * If the bpp is in units of 1/16, further divide by 16. Put this
+	 * factor in the numerator rather than the denominator to avoid
+	 * integer overflow
 	 */
 
 	numerator = 64 * 1006;
 	denominator = 54 * 8 * 1000 * 1000;
 
+	if (dsc)
+		numerator /= 16;
+
 	kbps *= numerator;
 	peak_kbps = drm_fixp_from_fraction(kbps, denominator);
 
@@ -3567,19 +3575,19 @@ EXPORT_SYMBOL(drm_dp_calc_pbn_mode);
 static int test_calc_pbn_mode(void)
 {
 	int ret;
-	ret = drm_dp_calc_pbn_mode(154000, 30);
+	ret = drm_dp_calc_pbn_mode(154000, 30, false);
 	if (ret != 689) {
 		DRM_ERROR("PBN calculation test failed - clock %d, bpp %d, expected PBN %d, actual PBN %d.\n",
 				154000, 30, 689, ret);
 		return -EINVAL;
 	}
-	ret = drm_dp_calc_pbn_mode(234000, 30);
+	ret = drm_dp_calc_pbn_mode(234000, 30, false);
 	if (ret != 1047) {
 		DRM_ERROR("PBN calculation test failed - clock %d, bpp %d, expected PBN %d, actual PBN %d.\n",
 				234000, 30, 1047, ret);
 		return -EINVAL;
 	}
-	ret = drm_dp_calc_pbn_mode(297000, 24);
+	ret = drm_dp_calc_pbn_mode(297000, 24, false);
 	if (ret != 1063) {
 		DRM_ERROR("PBN calculation test failed - clock %d, bpp %d, expected PBN %d, actual PBN %d.\n",
 				297000, 24, 1063, ret);
diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c
index 8839eaea8371..2a692c2141bf 100644
--- a/drivers/gpu/drm/i915/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/intel_dp_mst.c
@@ -58,7 +58,8 @@ static int intel_dp_mst_compute_link_config(struct intel_encoder *encoder,
 		crtc_state->pipe_bpp = bpp;
 
 		crtc_state->pbn = drm_dp_calc_pbn_mode(adjusted_mode->crtc_clock,
-						       crtc_state->pipe_bpp);
+						       crtc_state->pipe_bpp,
+						       false);
 
 		slots = drm_dp_atomic_find_vcpi_slots(state, &intel_dp->mst_mgr,
 						      port, crtc_state->pbn);
diff --git a/drivers/gpu/drm/nouveau/dispnv50/disp.c b/drivers/gpu/drm/nouveau/dispnv50/disp.c
index 4b1650f51955..ec8bb491e576 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
@@ -773,7 +773,8 @@ nv50_msto_atomic_check(struct drm_encoder *encoder,
 	if (!state->duplicated)
 		asyh->dp.pbn =
 			drm_dp_calc_pbn_mode(crtc_state->adjusted_mode.clock,
-					     connector->display_info.bpc * 3);
+					     connector->display_info.bpc * 3,
+					     false);
 
 	if (drm_atomic_crtc_needs_modeset(crtc_state)) {
 		slots = drm_dp_atomic_find_vcpi_slots(state, &mstm->mgr,
diff --git a/drivers/gpu/drm/radeon/radeon_dp_mst.c b/drivers/gpu/drm/radeon/radeon_dp_mst.c
index 8d85540bbb43..384d0c9373c4 100644
--- a/drivers/gpu/drm/radeon/radeon_dp_mst.c
+++ b/drivers/gpu/drm/radeon/radeon_dp_mst.c
@@ -513,7 +513,7 @@ static bool radeon_mst_mode_fixup(struct drm_encoder *encoder,
 
 	mst_enc = radeon_encoder->enc_priv;
 
-	mst_enc->pbn = drm_dp_calc_pbn_mode(adjusted_mode->clock, bpp);
+	mst_enc->pbn = drm_dp_calc_pbn_mode(adjusted_mode->clock, bpp, false);
 
 	mst_enc->primary->active_device = mst_enc->primary->devices & mst_enc->connector->devices;
 	DRM_DEBUG_KMS("setting active device to %08x from %08x %08x for encoder %d\n",
diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
index 2ba6253ea6d3..9116b2c95239 100644
--- a/include/drm/drm_dp_mst_helper.h
+++ b/include/drm/drm_dp_mst_helper.h
@@ -610,8 +610,7 @@ bool drm_dp_mst_port_has_audio(struct drm_dp_mst_topology_mgr *mgr,
 struct edid *drm_dp_mst_get_edid(struct drm_connector *connector, struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port);
 
 
-int drm_dp_calc_pbn_mode(int clock, int bpp);
-
+int drm_dp_calc_pbn_mode(int clock, int bpp, bool dsc);
 
 bool drm_dp_mst_allocate_vcpi(struct drm_dp_mst_topology_mgr *mgr,
 			      struct drm_dp_mst_port *port, int pbn, int slots);
-- 
2.17.1

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[PATCH 05/15] drm/dp_mst: Parse FEC capability on MST ports

[mikita.lipski-5C7GfCeVMHo]

From: David Francis <David.Francis@amd.com>

As of DP1.4, ENUM_PATH_RESOURCES returns a bit indicating
if FEC can be supported up to that point in the MST network.

The bit is the first byte of the ENUM_PATH_RESOURCES ack reply,
bottom-most bit (refer to section 2.11.9.4 of DP standard,
v1.4)

That value is needed for FEC and DSC support

Store it on drm_dp_mst_port

Signed-off-by: David Francis <David.Francis@amd.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 2 ++
 include/drm/drm_dp_mst_helper.h       | 3 +++
 2 files changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 659099366f8b..c1a7ddfdc4bd 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -552,6 +552,7 @@ static bool drm_dp_sideband_parse_enum_path_resources_ack(struct drm_dp_sideband
 {
 	int idx = 1;
 	repmsg->u.path_resources.port_number = (raw->msg[idx] >> 4) & 0xf;
+	repmsg->u.path_resources.fec_capable = raw->msg[idx] & 0x1;
 	idx++;
 	if (idx > raw->curlen)
 		goto fail_len;
@@ -2180,6 +2181,7 @@ static int drm_dp_send_enum_path_resources(struct drm_dp_mst_topology_mgr *mgr,
 			DRM_DEBUG_KMS("enum path resources %d: %d %d\n", txmsg->reply.u.path_resources.port_number, txmsg->reply.u.path_resources.full_payload_bw_number,
 			       txmsg->reply.u.path_resources.avail_payload_bw_number);
 			port->available_pbn = txmsg->reply.u.path_resources.avail_payload_bw_number;
+			port->fec_capable = txmsg->reply.u.path_resources.fec_capable;
 		}
 	}
 
diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
index 9116b2c95239..f113ae04fa88 100644
--- a/include/drm/drm_dp_mst_helper.h
+++ b/include/drm/drm_dp_mst_helper.h
@@ -108,6 +108,8 @@ struct drm_dp_mst_port {
 	 * audio-capable.
 	 */
 	bool has_audio;
+
+	bool fec_capable;
 };
 
 /**
@@ -312,6 +314,7 @@ struct drm_dp_port_number_req {
 
 struct drm_dp_enum_path_resources_ack_reply {
 	u8 port_number;
+	bool fec_capable;
 	u16 full_payload_bw_number;
 	u16 avail_payload_bw_number;
 };
-- 
2.17.1

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[PATCH 06/15] drm/dp_mst: Add MST support to DP DPCD R/W functions

[mikita.lipski-5C7GfCeVMHo]

From: David Francis <David.Francis@amd.com>

Instead of having drm_dp_dpcd_read/write and
drm_dp_mst_dpcd_read/write as entry points into the
aux code, have drm_dp_dpcd_read/write handle both.

This means that DRM drivers can make MST DPCD read/writes.

v2: Fix spacing
v3: Dump dpcd access on MST read/writes

Reviewed-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: David Francis <David.Francis@amd.com>
---
 drivers/gpu/drm/drm_dp_aux_dev.c | 12 ++----------
 drivers/gpu/drm/drm_dp_helper.c  | 30 ++++++++++++++++++++----------
 2 files changed, 22 insertions(+), 20 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_aux_dev.c b/drivers/gpu/drm/drm_dp_aux_dev.c
index 00610bd8d6c1..0780fc358389 100644
--- a/drivers/gpu/drm/drm_dp_aux_dev.c
+++ b/drivers/gpu/drm/drm_dp_aux_dev.c
@@ -162,11 +162,7 @@ static ssize_t auxdev_read_iter(struct kiocb *iocb, struct iov_iter *to)
 			break;
 		}
 
-		if (aux_dev->aux->is_remote)
-			res = drm_dp_mst_dpcd_read(aux_dev->aux, pos, buf,
-						   todo);
-		else
-			res = drm_dp_dpcd_read(aux_dev->aux, pos, buf, todo);
+		res = drm_dp_dpcd_read(aux_dev->aux, pos, buf, todo);
 
 		if (res <= 0)
 			break;
@@ -214,11 +210,7 @@ static ssize_t auxdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
 			break;
 		}
 
-		if (aux_dev->aux->is_remote)
-			res = drm_dp_mst_dpcd_write(aux_dev->aux, pos, buf,
-						    todo);
-		else
-			res = drm_dp_dpcd_write(aux_dev->aux, pos, buf, todo);
+		res = drm_dp_mst_dpcd_write(aux_dev->aux, pos, buf, todo);
 
 		if (res <= 0)
 			break;
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 54a6414c5d96..0cbf10727bd6 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -29,6 +29,7 @@
 #include <linux/i2c.h>
 #include <linux/seq_file.h>
 #include <drm/drm_dp_helper.h>
+#include <drm/drm_dp_mst_helper.h>
 #include <drm/drmP.h>
 
 #include "drm_crtc_helper_internal.h"
@@ -272,7 +273,7 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request,
 
 /**
  * drm_dp_dpcd_read() - read a series of bytes from the DPCD
- * @aux: DisplayPort AUX channel
+ * @aux: DisplayPort AUX channel (SST or MST)
  * @offset: address of the (first) register to read
  * @buffer: buffer to store the register values
  * @size: number of bytes in @buffer
@@ -301,13 +302,18 @@ ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,
 	 * We just have to do it before any DPCD access and hope that the
 	 * monitor doesn't power down exactly after the throw away read.
 	 */
-	ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, DP_DPCD_REV, buffer,
-				 1);
-	if (ret != 1)
-		goto out;
+	if (!aux->is_remote) {
+		ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, DP_DPCD_REV,
+					 buffer, 1);
+		if (ret != 1)
+			goto out;
+	}
 
-	ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, offset, buffer,
-				 size);
+	if (aux->is_remote)
+		ret = drm_dp_mst_dpcd_read(aux, offset, buffer, size);
+	else
+		ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, offset,
+					 buffer, size);
 
 out:
 	drm_dp_dump_access(aux, DP_AUX_NATIVE_READ, offset, buffer, ret);
@@ -317,7 +323,7 @@ EXPORT_SYMBOL(drm_dp_dpcd_read);
 
 /**
  * drm_dp_dpcd_write() - write a series of bytes to the DPCD
- * @aux: DisplayPort AUX channel
+ * @aux: DisplayPort AUX channel (SST or MST)
  * @offset: address of the (first) register to write
  * @buffer: buffer containing the values to write
  * @size: number of bytes in @buffer
@@ -334,8 +340,12 @@ ssize_t drm_dp_dpcd_write(struct drm_dp_aux *aux, unsigned int offset,
 {
 	int ret;
 
-	ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_WRITE, offset, buffer,
-				 size);
+	if (aux->is_remote)
+		ret = drm_dp_mst_dpcd_write(aux, offset, buffer, size);
+	else
+		ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_WRITE, offset,
+					 buffer, size);
+
 	drm_dp_dump_access(aux, DP_AUX_NATIVE_WRITE, offset, buffer, ret);
 	return ret;
 }
-- 
2.17.1

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[PATCH 07/15] drm/dp_mst: Fill branch->num_ports

[mikita.lipski-5C7GfCeVMHo]

From: David Francis <David.Francis@amd.com>

This field on drm_dp_mst_branch was never filled

It is initialized to zero when the port is kzallocced.
When a port is added to the list, increment num_ports,
and when a port is removed from the list, decrement num_ports.

v2: remember to decrement on port removal
v3: don't explicitly init to 0

Signed-off-by: David Francis <David.Francis@amd.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index c1a7ddfdc4bd..ae2f986d76a2 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -1670,6 +1670,7 @@ static void drm_dp_add_port(struct drm_dp_mst_branch *mstb,
 		mutex_lock(&mstb->mgr->lock);
 		drm_dp_mst_topology_get_port(port);
 		list_add(&port->next, &mstb->ports);
+		mstb->num_ports++;
 		mutex_unlock(&mstb->mgr->lock);
 	}
 
@@ -1704,6 +1705,7 @@ static void drm_dp_add_port(struct drm_dp_mst_branch *mstb,
 			/* remove it from the port list */
 			mutex_lock(&mstb->mgr->lock);
 			list_del(&port->next);
+			mstb->num_ports--;
 			mutex_unlock(&mstb->mgr->lock);
 			/* drop port list reference */
 			drm_dp_mst_topology_put_port(port);
-- 
2.17.1

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[PATCH 09/15] drm/dp_mst: Add new quirk for Synaptics MST hubs

[mikita.lipski-5C7GfCeVMHo]

From: David Francis <David.Francis@amd.com>

Synaptics DP1.4 hubs (BRANCH_ID 0x90CC24) do not
support virtual DPCD registers, but do support DSC.
The DSC caps can be read from the physical aux,
like in SST DSC. These hubs have many different
DEVICE_IDs.  Add a new quirk to detect this case.

Change-Id: I9d332f273dfca0cfbced111e62f5a06c5c312893
Cc: Lyude Paul <lyude@redhat.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com>
Signed-off-by: David Francis <David.Francis@amd.com>
---
 drivers/gpu/drm/drm_dp_helper.c       |  4 +++-
 drivers/gpu/drm/drm_dp_mst_topology.c | 27 +++++++++++++++++++++++++++
 include/drm/drm_dp_helper.h           |  7 +++++++
 3 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 0cbf10727bd6..c3e1da78e442 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -1288,7 +1288,9 @@ static const struct dpcd_quirk dpcd_quirk_list[] = {
 	/* LG LP140WF6-SPM1 eDP panel */
 	{ OUI(0x00, 0x22, 0xb9), DEVICE_ID('s', 'i', 'v', 'a', 'r', 'T'), false, BIT(DP_DPCD_QUIRK_CONSTANT_N) },
 	/* Apple panels need some additional handling to support PSR */
-	{ OUI(0x00, 0x10, 0xfa), DEVICE_ID_ANY, false, BIT(DP_DPCD_QUIRK_NO_PSR) }
+	{ OUI(0x00, 0x10, 0xfa), DEVICE_ID_ANY, false, BIT(DP_DPCD_QUIRK_NO_PSR) },
+	/* Synaptics DP1.4 MST hubs can support DSC without virtual DPCD */
+	{ OUI(0x90, 0xCC, 0x24), DEVICE_ID_ANY, true, BIT(DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD) },
 };
 
 #undef OUI
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index dd2ca065cc92..4e493d8af288 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -4219,6 +4219,7 @@ struct drm_dp_aux *drm_dp_mst_dsc_aux_for_port(struct drm_dp_mst_port *port)
 {
 	struct drm_dp_mst_port *immediate_upstream_port;
 	struct drm_dp_mst_port *fec_port;
+	struct drm_dp_desc desc = { 0 };
 
 	if (!port)
 		return NULL;
@@ -4271,6 +4272,32 @@ struct drm_dp_aux *drm_dp_mst_dsc_aux_for_port(struct drm_dp_mst_port *port)
 	if (drm_dp_mst_is_virtual_dpcd(port))
 		return &port->aux;
 
+	/*
+	 * Synaptics quirk
+	 * Applies to ports for which:
+	 * - Physical aux has Synaptics OUI
+	 * - DPv1.4 or higher
+	 * - Port is on primary branch device
+	 * - Not a VGA adapter (DP_DWN_STRM_PORT_TYPE_ANALOG)
+	 */
+	if (!drm_dp_read_desc(port->mgr->aux, &desc, true))
+		return NULL;
+
+	if (drm_dp_has_quirk(&desc, DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD) &&
+	    port->mgr->dpcd[DP_DPCD_REV] >= DP_DPCD_REV_14 &&
+	    port->parent == port->mgr->mst_primary) {
+		u8 downstreamport;
+
+		if (drm_dp_dpcd_read(&port->aux, DP_DOWNSTREAMPORT_PRESENT,
+				     &downstreamport, 1) < 0)
+			return NULL;
+
+		if ((downstreamport & DP_DWN_STRM_PORT_PRESENT) &&
+		   ((downstreamport & DP_DWN_STRM_PORT_TYPE_MASK)
+		     != DP_DWN_STRM_PORT_TYPE_ANALOG))
+			return port->mgr->aux;
+	}
+
 	return NULL;
 }
 EXPORT_SYMBOL(drm_dp_mst_dsc_aux_for_port);
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index 6ae1a6765f63..919ad940bfb1 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -1414,6 +1414,13 @@ enum drm_dp_quirk {
 	 * driver still need to implement proper handling for such device.
 	 */
 	DP_DPCD_QUIRK_NO_PSR,
+	/**
+	 * @DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD:
+	 *
+	 * The device supports MST DSC despite not supporting Virtual DPCD.
+	 * The DSC caps can be read from the physical aux instead.
+	 */
+	DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD,
 };
 
 /**
-- 
2.17.1

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Re: [PATCH 09/15] drm/dp_mst: Add new quirk for Synaptics MST hubs

[Lyude Paul]

Great work!

Reviewed-by: Lyude Paul <lyude@redhat.com>

On Wed, 2019-09-18 at 16:26 -0400, mikita.lipski@amd.com wrote:
> From: David Francis <David.Francis@amd.com>
> 
> Synaptics DP1.4 hubs (BRANCH_ID 0x90CC24) do not
> support virtual DPCD registers, but do support DSC.
> The DSC caps can be read from the physical aux,
> like in SST DSC. These hubs have many different
> DEVICE_IDs.  Add a new quirk to detect this case.
> 
> Change-Id: I9d332f273dfca0cfbced111e62f5a06c5c312893
> Cc: Lyude Paul <lyude@redhat.com>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Harry Wentland <harry.wentland@amd.com>
> Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com>
> Signed-off-by: David Francis <David.Francis@amd.com>
> ---
>  drivers/gpu/drm/drm_dp_helper.c       |  4 +++-
>  drivers/gpu/drm/drm_dp_mst_topology.c | 27 +++++++++++++++++++++++++++
>  include/drm/drm_dp_helper.h           |  7 +++++++
>  3 files changed, 37 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_dp_helper.c
> b/drivers/gpu/drm/drm_dp_helper.c
> index 0cbf10727bd6..c3e1da78e442 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -1288,7 +1288,9 @@ static const struct dpcd_quirk dpcd_quirk_list[] = {
>  	/* LG LP140WF6-SPM1 eDP panel */
>  	{ OUI(0x00, 0x22, 0xb9), DEVICE_ID('s', 'i', 'v', 'a', 'r', 'T'),
> false, BIT(DP_DPCD_QUIRK_CONSTANT_N) },
>  	/* Apple panels need some additional handling to support PSR */
> -	{ OUI(0x00, 0x10, 0xfa), DEVICE_ID_ANY, false,
> BIT(DP_DPCD_QUIRK_NO_PSR) }
> +	{ OUI(0x00, 0x10, 0xfa), DEVICE_ID_ANY, false,
> BIT(DP_DPCD_QUIRK_NO_PSR) },
> +	/* Synaptics DP1.4 MST hubs can support DSC without virtual DPCD */
> +	{ OUI(0x90, 0xCC, 0x24), DEVICE_ID_ANY, true,
> BIT(DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD) },
>  };
>  
>  #undef OUI
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c
> b/drivers/gpu/drm/drm_dp_mst_topology.c
> index dd2ca065cc92..4e493d8af288 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -4219,6 +4219,7 @@ struct drm_dp_aux *drm_dp_mst_dsc_aux_for_port(struct
> drm_dp_mst_port *port)
>  {
>  	struct drm_dp_mst_port *immediate_upstream_port;
>  	struct drm_dp_mst_port *fec_port;
> +	struct drm_dp_desc desc = { 0 };
>  
>  	if (!port)
>  		return NULL;
> @@ -4271,6 +4272,32 @@ struct drm_dp_aux *drm_dp_mst_dsc_aux_for_port(struct
> drm_dp_mst_port *port)
>  	if (drm_dp_mst_is_virtual_dpcd(port))
>  		return &port->aux;
>  
> +	/*
> +	 * Synaptics quirk
> +	 * Applies to ports for which:
> +	 * - Physical aux has Synaptics OUI
> +	 * - DPv1.4 or higher
> +	 * - Port is on primary branch device
> +	 * - Not a VGA adapter (DP_DWN_STRM_PORT_TYPE_ANALOG)
> +	 */
> +	if (!drm_dp_read_desc(port->mgr->aux, &desc, true))
> +		return NULL;
> +
> +	if (drm_dp_has_quirk(&desc, DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD) &&
> +	    port->mgr->dpcd[DP_DPCD_REV] >= DP_DPCD_REV_14 &&
> +	    port->parent == port->mgr->mst_primary) {
> +		u8 downstreamport;
> +
> +		if (drm_dp_dpcd_read(&port->aux, DP_DOWNSTREAMPORT_PRESENT,
> +				     &downstreamport, 1) < 0)
> +			return NULL;
> +
> +		if ((downstreamport & DP_DWN_STRM_PORT_PRESENT) &&
> +		   ((downstreamport & DP_DWN_STRM_PORT_TYPE_MASK)
> +		     != DP_DWN_STRM_PORT_TYPE_ANALOG))
> +			return port->mgr->aux;
> +	}
> +
>  	return NULL;
>  }
>  EXPORT_SYMBOL(drm_dp_mst_dsc_aux_for_port);
> diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
> index 6ae1a6765f63..919ad940bfb1 100644
> --- a/include/drm/drm_dp_helper.h
> +++ b/include/drm/drm_dp_helper.h
> @@ -1414,6 +1414,13 @@ enum drm_dp_quirk {
>  	 * driver still need to implement proper handling for such device.
>  	 */
>  	DP_DPCD_QUIRK_NO_PSR,
> +	/**
> +	 * @DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD:
> +	 *
> +	 * The device supports MST DSC despite not supporting Virtual DPCD.
> +	 * The DSC caps can be read from the physical aux instead.
> +	 */
> +	DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD,
>  };
>  
>  /**
-- 
Cheers,
	Lyude Paul

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[PATCH 11/15] drm/amd/display: Initialize DSC PPS variables to 0

[mikita.lipski-5C7GfCeVMHo]

From: David Francis <David.Francis@amd.com>

For DSC MST, sometimes monitors would break out
in full-screen static. The issue traced back to the
PPS generation code, where these variables were being used
uninitialized and were picking up garbage.

memset to 0 to avoid this

Signed-off-by: David Francis <David.Francis@amd.com>
Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
---
 drivers/gpu/drm/amd/display/dc/core/dc_link_hwss.c | 3 +++
 drivers/gpu/drm/amd/display/dc/dcn20/dcn20_dsc.c   | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_hwss.c b/drivers/gpu/drm/amd/display/dc/core/dc_link_hwss.c
index a519dbc5ecb6..5d6cbaebebc0 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link_hwss.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_hwss.c
@@ -496,6 +496,9 @@ bool dp_set_dsc_pps_sdp(struct pipe_ctx *pipe_ctx, bool enable)
 		struct dsc_config dsc_cfg;
 		uint8_t dsc_packed_pps[128];
 
+		memset(&dsc_cfg, 0, sizeof(dsc_cfg));
+		memset(dsc_packed_pps, 0, 128);
+
 		/* Enable DSC hw block */
 		dsc_cfg.pic_width = stream->timing.h_addressable + stream->timing.h_border_left + stream->timing.h_border_right;
 		dsc_cfg.pic_height = stream->timing.v_addressable + stream->timing.v_border_top + stream->timing.v_border_bottom;
diff --git a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_dsc.c b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_dsc.c
index 63eb377ed9c0..296eeff00296 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_dsc.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_dsc.c
@@ -207,6 +207,9 @@ static bool dsc2_get_packed_pps(struct display_stream_compressor *dsc, const str
 	struct dsc_reg_values dsc_reg_vals;
 	struct dsc_optc_config dsc_optc_cfg;
 
+	memset(&dsc_reg_vals, 0, sizeof(dsc_reg_vals));
+	memset(&dsc_optc_cfg, 0, sizeof(dsc_optc_cfg));
+
 	DC_LOG_DSC("Getting packed DSC PPS for DSC Config:");
 	dsc_config_log(dsc, dsc_cfg);
 	DC_LOG_DSC("DSC Picture Parameter Set (PPS):");
-- 
2.17.1

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[PATCH 13/15] drm/amd/display: Write DSC enable to MST DPCD

[mikita.lipski-5C7GfCeVMHo]

From: David Francis <David.Francis@amd.com>

Rework the dm_helpers_write_dsc_enable callback to
handle the MST case.

Use the cached dsc_aux field.

Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com>
Signed-off-by: David Francis <David.Francis@amd.com>
---
 .../amd/display/amdgpu_dm/amdgpu_dm_helpers.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
index aaf3158534ab..a83d7da259fe 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
@@ -38,6 +38,7 @@
 #include "dc.h"
 #include "amdgpu_dm.h"
 #include "amdgpu_dm_irq.h"
+#include "amdgpu_dm_mst_types.h"
 
 #include "dm_helpers.h"
 
@@ -557,8 +558,24 @@ bool dm_helpers_dp_write_dsc_enable(
 )
 {
 	uint8_t enable_dsc = enable ? 1 : 0;
+	struct amdgpu_dm_connector *aconnector;
+
+	if (!stream)
+		return false;
+
+	if (stream->signal == SIGNAL_TYPE_DISPLAY_PORT_MST) {
+		aconnector = (struct amdgpu_dm_connector *)stream->dm_stream_context;
+
+		if (!aconnector->dsc_aux)
+			return false;
+
+		return (drm_dp_dpcd_write(aconnector->dsc_aux, DP_DSC_ENABLE, &enable_dsc, 1) >= 0);
+	}
+
+	if (stream->signal == SIGNAL_TYPE_DISPLAY_PORT)
+		return dm_helpers_dp_write_dpcd(ctx, stream->link, DP_DSC_ENABLE, &enable_dsc, 1);
 
-	return dm_helpers_dp_write_dpcd(ctx, stream->sink->link, DP_DSC_ENABLE, &enable_dsc, 1);
+	return false;
 }
 #endif
 
-- 
2.17.1

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[PATCH 14/15] drm/amd/display: MST DSC compute fair share

[mikita.lipski-5C7GfCeVMHo]

From: David Francis <David.Francis@amd.com>

If there is limited link bandwidth on a MST network,
it must be divided fairly between the streams on that network

Implement an algorithm to determine the correct DSC config
for each stream

The algorithm:
This
     [                   ]          ( )
represents the range of bandwidths possible for a given stream.
The [] area represents the range of DSC configs, and the ()
represents no DSC. The bandwidth used increases from left to right.

First, try disabling DSC on all streams
     [                  ]          (|)
     [                     ]            (|)
Check this against the bandwidth limits of the link and each branch
(including each endpoint). If it passes, the job is done

Second, try maximum DSC compression on all streams
that support DSC
     [|         ]        ( )
     [|                ]         ( )
If this does not pass, then enabling this combination of streams
is impossible

Otherwise, divide the remaining bandwidth evenly amongst the streams
     [        |  ]         ( )
     [        |      ]        ( )

If one or more of the streams reach minimum compression, evenly
divide the reamining bandwidth amongst the remaining streams
     [    |] ( )
     [       |]   ( )
     [                 |   ]               ( )
     [                 |      ]                  ( )

If all streams can reach minimum compression, disable compression
greedily
     [      |]  ( )
     [        |]    ( )
     [                 ]                                (|)

Perform this algorithm on each full update, on each MST link
with at least one DSC stream on it

After the configs are computed, call
dcn20_add_dsc_to_stream_resource on each stream with DSC enabled.
It is only after all streams are created that we can know which
of them will need DSC.

Do all of this at the end of amdgpu atomic check.  If it fails,
fail check; This combination of timings cannot be supported.

Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com>
Signed-off-by: David Francis <David.Francis@amd.com>
---
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |   4 +
 .../display/amdgpu_dm/amdgpu_dm_mst_types.c   | 386 ++++++++++++++++++
 .../display/amdgpu_dm/amdgpu_dm_mst_types.h   |   4 +
 .../drm/amd/display/dc/dcn20/dcn20_resource.c |   7 +-
 .../drm/amd/display/dc/dcn20/dcn20_resource.h |   1 +
 5 files changed, 400 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 1130298c6930..ba017e6bf0b4 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -7564,6 +7564,10 @@ static int amdgpu_dm_atomic_check(struct drm_device *dev,
 		if (ret)
 			goto fail;
 
+#ifdef CONFIG_DRM_AMD_DC_DSC_SUPPORT
+		if (!compute_mst_dsc_configs_for_state(dm_state->context))
+			goto fail;
+#endif
 		if (dc_validate_global_state(dc, dm_state->context, false) != DC_OK) {
 			ret = -EINVAL;
 			goto fail;
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
index 379bc5f388f7..0356688c5ebf 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
@@ -38,6 +38,8 @@
 
 #include "i2caux_interface.h"
 
+#include "dc/dcn20/dcn20_resource.h"
+
 /* #define TRACE_DPCD */
 
 #ifdef TRACE_DPCD
@@ -490,3 +492,387 @@ void amdgpu_dm_initialize_dp_connector(struct amdgpu_display_manager *dm,
 		aconnector->connector_id);
 }
 
+#ifdef CONFIG_DRM_AMD_DC_DSC_SUPPORT
+struct dsc_mst_fairness_params {
+	struct dc_crtc_timing *timing;
+	struct dc_sink *sink;
+	struct dc_dsc_bw_range bw_range;
+	bool compression_possible;
+	struct drm_dp_mst_port *port;
+};
+
+struct dsc_mst_fairness_vars {
+	int pbn;
+	bool dsc_enabled;
+	int bpp_x16;
+};
+
+static bool port_downstream_of_branch(struct drm_dp_mst_port *port,
+		struct drm_dp_mst_branch *branch)
+{
+	while (port->parent) {
+		if (port->parent == branch)
+			return true;
+
+		if (port->parent->port_parent)
+			port = port->parent->port_parent;
+		else
+			break;
+	}
+	return false;
+}
+
+static bool check_pbn_limit_on_branch(struct drm_dp_mst_branch *branch,
+		struct dsc_mst_fairness_params *params,
+		struct dsc_mst_fairness_vars *vars, int count)
+{
+	struct drm_dp_mst_port *port;
+	int i;
+	int pbn_limit = 0;
+	int pbn_used = 0;
+
+	list_for_each_entry(port, &branch->ports, next) {
+		if (port->mstb)
+			if (!check_pbn_limit_on_branch(port->mstb, params, vars, count))
+				return false;
+
+		if (port->available_pbn > 0)
+			pbn_limit = port->available_pbn;
+	}
+
+	for (i = 0; i < count; i++) {
+		if (port_downstream_of_branch(params[i].port, branch))
+			pbn_used += vars[i].pbn;
+	}
+
+	if (pbn_used > pbn_limit)
+		return false;
+
+	return true;
+}
+
+static bool check_bandwidth_limits(struct dc_link *dc_link,
+		struct dsc_mst_fairness_params *params,
+		struct dsc_mst_fairness_vars *vars,
+		int count)
+{
+	int link_timeslot_limit = 63;
+	int link_timeslots_used = 0;
+	int pbn_per_timeslot;
+	int i;
+	struct drm_dp_mst_topology_mgr *mst_mgr;
+
+	/* kbits to pbn, dividing by 64 */
+	pbn_per_timeslot = dc_link_bandwidth_kbps(dc_link,
+			dc_link_get_link_cap(dc_link)) / (8 * 1000 * 54);
+
+	/* Check link bandwidth limit */
+	for (i = 0; i < count; i++)
+		link_timeslots_used += DIV_ROUND_UP(vars[i].pbn, pbn_per_timeslot);
+
+	if (link_timeslots_used > link_timeslot_limit)
+		return false;
+
+	/* Check branch bandwidth limit for each port on each branch */
+	mst_mgr = params[0].port->mgr;
+	if (!check_pbn_limit_on_branch(mst_mgr->mst_primary, params, vars, count))
+		return false;
+
+	return true;
+}
+
+static int kbps_to_peak_pbn(int kbps)
+{
+	u64 peak_kbps = kbps;
+
+	peak_kbps *= 1006;
+	peak_kbps /= 1000;
+	return (int) DIV_ROUND_UP(peak_kbps * 64, (54 * 8 * 1000));
+}
+
+static void set_dsc_configs_from_fairness_vars(struct dsc_mst_fairness_params *params,
+		struct dsc_mst_fairness_vars *vars,
+		int count)
+{
+	int i;
+
+	for (i = 0; i < count; i++) {
+		memset(&params[i].timing->dsc_cfg, 0, sizeof(params[i].timing->dsc_cfg));
+		if (vars[i].dsc_enabled && dc_dsc_compute_config(
+					params[i].sink->ctx->dc->res_pool->dscs[0],
+					&params[i].sink->sink_dsc_caps.dsc_dec_caps,
+					params[i].sink->ctx->dc->debug.dsc_min_slice_height_override,
+					0,
+					params[i].timing,
+					&params[i].timing->dsc_cfg)) {
+			params[i].timing->flags.DSC = 1;
+			params[i].timing->dsc_cfg.bits_per_pixel = vars[i].bpp_x16;
+		} else {
+			params[i].timing->flags.DSC = 0;
+		}
+
+	}
+
+}
+
+static int bpp_x16_from_pbn(struct dsc_mst_fairness_params param, int pbn)
+{
+	struct dc_dsc_config dsc_config;
+	u64 kbps;
+
+	kbps = (u64)pbn * 994 * 8 * 54 / 64;
+	dc_dsc_compute_config(
+			param.sink->ctx->dc->res_pool->dscs[0],
+			&param.sink->sink_dsc_caps.dsc_dec_caps,
+			param.sink->ctx->dc->debug.dsc_min_slice_height_override,
+			(int) kbps, param.timing, &dsc_config);
+
+	return dsc_config.bits_per_pixel;
+}
+
+static void increase_dsc_bpp(struct dc_link *dc_link,
+		struct dsc_mst_fairness_params *params,
+		struct dsc_mst_fairness_vars *vars,
+		int count)
+{
+	int i;
+	bool bpp_increased[MAX_PIPES];
+	int initial_slack[MAX_PIPES];
+	int min_initial_slack;
+	int next_index;
+	int remaining_to_increase = 0;
+	int pbn_per_timeslot;
+	int link_timeslots_used;
+	int fair_pbn_alloc;
+
+	for (i = 0; i < count; i++) {
+		if (vars[i].dsc_enabled) {
+			initial_slack[i] = kbps_to_peak_pbn(params[i].bw_range.max_kbps) - vars[i].pbn;
+			bpp_increased[i] = false;
+			remaining_to_increase += 1;
+		} else {
+			initial_slack[i] = 0;
+			bpp_increased[i] = true;
+		}
+	}
+
+	pbn_per_timeslot = dc_link_bandwidth_kbps(dc_link,
+			dc_link_get_link_cap(dc_link)) / (8 * 1000 * 54);
+
+	while (remaining_to_increase) {
+		next_index = -1;
+		min_initial_slack = -1;
+		for (i = 0; i < count; i++) {
+			if (!bpp_increased[i]) {
+				if (min_initial_slack == -1 || min_initial_slack > initial_slack[i]) {
+					min_initial_slack = initial_slack[i];
+					next_index = i;
+				}
+			}
+		}
+
+		if (next_index == -1)
+			break;
+
+		link_timeslots_used = 0;
+
+		for (i = 0; i < count; i++)
+			link_timeslots_used += DIV_ROUND_UP(vars[i].pbn, pbn_per_timeslot);
+
+		fair_pbn_alloc = (63 - link_timeslots_used) / remaining_to_increase * pbn_per_timeslot;
+
+		if (initial_slack[next_index] > fair_pbn_alloc) {
+			vars[next_index].pbn += fair_pbn_alloc;
+			if (check_bandwidth_limits(dc_link, params, vars, count))
+				vars[next_index].bpp_x16 = bpp_x16_from_pbn(params[next_index], vars[next_index].pbn);
+			else
+				vars[next_index].pbn -= fair_pbn_alloc;
+		} else {
+			vars[next_index].pbn += initial_slack[next_index];
+			if (check_bandwidth_limits(dc_link, params, vars, count))
+				vars[next_index].bpp_x16 = params[next_index].bw_range.max_target_bpp_x16;
+			else
+				vars[next_index].pbn -= initial_slack[next_index];
+		}
+
+		bpp_increased[next_index] = true;
+		remaining_to_increase--;
+	}
+}
+
+static void try_disable_dsc(struct dc_link *dc_link,
+		struct dsc_mst_fairness_params *params,
+		struct dsc_mst_fairness_vars *vars,
+		int count)
+{
+	int i;
+	bool tried[MAX_PIPES];
+	int kbps_increase[MAX_PIPES];
+	int max_kbps_increase;
+	int next_index;
+	int remaining_to_try = 0;
+
+	for (i = 0; i < count; i++) {
+		if (vars[i].dsc_enabled && vars[i].bpp_x16 == params[i].bw_range.max_target_bpp_x16) {
+			kbps_increase[i] = params[i].bw_range.stream_kbps - params[i].bw_range.max_kbps;
+			tried[i] = false;
+			remaining_to_try += 1;
+		} else {
+			kbps_increase[i] = 0;
+			tried[i] = true;
+		}
+	}
+
+	while (remaining_to_try) {
+		next_index = -1;
+		max_kbps_increase = -1;
+		for (i = 0; i < count; i++) {
+			if (!tried[i]) {
+				if (max_kbps_increase == -1 || max_kbps_increase < kbps_increase[i]) {
+					max_kbps_increase = kbps_increase[i];
+					next_index = i;
+				}
+			}
+		}
+
+		if (next_index == -1)
+			break;
+
+		vars[next_index].pbn = kbps_to_peak_pbn(params[next_index].bw_range.stream_kbps);
+
+		if (check_bandwidth_limits(dc_link, params, vars, count)) {
+			vars[next_index].dsc_enabled = false;
+			vars[next_index].bpp_x16 = 0;
+		} else {
+			vars[next_index].pbn = kbps_to_peak_pbn(params[next_index].bw_range.max_kbps);
+		}
+
+		tried[next_index] = true;
+		remaining_to_try--;
+	}
+}
+
+static bool compute_mst_dsc_configs_for_link(struct dc_state *dc_state, struct dc_link *dc_link)
+{
+	int i;
+	struct dc_stream_state *stream;
+	struct dsc_mst_fairness_params params[MAX_PIPES];
+	struct dsc_mst_fairness_vars vars[MAX_PIPES];
+	struct amdgpu_dm_connector *aconnector;
+	int count = 0;
+
+	memset(params, 0, sizeof(params));
+
+	/* Set up params */
+	for (i = 0; i < dc_state->stream_count; i++) {
+		stream = dc_state->streams[i];
+
+		if (stream->link != dc_link)
+			continue;
+
+		stream->timing.flags.DSC = 0;
+
+		params[count].timing = &stream->timing;
+		params[count].sink = stream->sink;
+		aconnector = (struct amdgpu_dm_connector *)stream->dm_stream_context;
+		params[count].port = aconnector->port;
+		params[count].compression_possible = stream->sink->sink_dsc_caps.dsc_dec_caps.is_dsc_supported;
+		if (!dc_dsc_compute_bandwidth_range(
+				stream->sink->ctx->dc->res_pool->dscs[0],
+				stream->sink->ctx->dc->debug.dsc_min_slice_height_override,
+				8, 16,
+				&stream->sink->sink_dsc_caps.dsc_dec_caps,
+				&stream->timing, &params[count].bw_range))
+			params[count].bw_range.stream_kbps = dc_bandwidth_in_kbps_from_timing(&stream->timing);
+
+		count++;
+	}
+
+	/* Try no compression */
+	for (i = 0; i < count; i++) {
+		vars[i].pbn = kbps_to_peak_pbn(params[i].bw_range.stream_kbps);
+		vars[i].dsc_enabled = false;
+		vars[i].bpp_x16 = 0;
+	}
+
+	if (check_bandwidth_limits(dc_link, params, vars, count)) {
+		set_dsc_configs_from_fairness_vars(params, vars, count);
+		return true;
+	}
+
+	/* Try max compression */
+	for (i = 0; i < count; i++) {
+		if (params[i].compression_possible) {
+			vars[i].pbn = kbps_to_peak_pbn(params[i].bw_range.min_kbps);
+			vars[i].dsc_enabled = true;
+			vars[i].bpp_x16 = params[i].bw_range.min_target_bpp_x16;
+		} else {
+			vars[i].pbn = kbps_to_peak_pbn(params[i].bw_range.stream_kbps);
+			vars[i].dsc_enabled = false;
+			vars[i].bpp_x16 = 0;
+		}
+	}
+
+	if (!check_bandwidth_limits(dc_link, params, vars, count))
+		return false;
+
+	/* Optimize degree of compression */
+	increase_dsc_bpp(dc_link, params, vars, count);
+
+	try_disable_dsc(dc_link, params, vars, count);
+
+	set_dsc_configs_from_fairness_vars(params, vars, count);
+
+	return true;
+}
+
+bool compute_mst_dsc_configs_for_state(struct dc_state *dc_state)
+{
+	int i, j;
+	struct dc_stream_state *stream;
+	bool computed_streams[MAX_PIPES];
+	struct amdgpu_dm_connector *aconnector;
+
+	for (i = 0; i < dc_state->stream_count; i++)
+		computed_streams[i] = false;
+
+	for (i = 0; i < dc_state->stream_count; i++) {
+		stream = dc_state->streams[i];
+
+		if (stream->signal != SIGNAL_TYPE_DISPLAY_PORT_MST)
+			continue;
+
+		aconnector = (struct amdgpu_dm_connector *)stream->dm_stream_context;
+
+		if (!aconnector || !aconnector->dc_sink)
+			continue;
+
+		if (!aconnector->dc_sink->sink_dsc_caps.dsc_dec_caps.is_dsc_supported)
+			continue;
+
+		if (computed_streams[i])
+			continue;
+
+		mutex_lock(&aconnector->mst_mgr.lock);
+		if (!compute_mst_dsc_configs_for_link(dc_state, stream->link)) {
+			mutex_unlock(&aconnector->mst_mgr.lock);
+			return false;
+		}
+		mutex_unlock(&aconnector->mst_mgr.lock);
+
+		for (j = 0; j < dc_state->stream_count; j++) {
+			if (dc_state->streams[j]->link == stream->link)
+				computed_streams[j] = true;
+		}
+	}
+
+	for (i = 0; i < dc_state->stream_count; i++) {
+		stream = dc_state->streams[i];
+
+		if (stream->timing.flags.DSC == 1)
+			dcn20_add_dsc_to_stream_resource(stream->ctx->dc, dc_state, stream);
+	}
+
+	return true;
+}
+#endif
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
index 2da851b40042..da957611214a 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
@@ -32,4 +32,8 @@ struct amdgpu_dm_connector;
 void amdgpu_dm_initialize_dp_connector(struct amdgpu_display_manager *dm,
 				       struct amdgpu_dm_connector *aconnector);
 
+
+#ifdef CONFIG_DRM_AMD_DC_DSC_SUPPORT
+bool compute_mst_dsc_configs_for_state(struct dc_state *dc_state);
+#endif
 #endif
diff --git a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c
index 8d81c65157d4..027933a24bb1 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c
@@ -1445,7 +1445,7 @@ static void release_dsc(struct resource_context *res_ctx,
 
 
 #ifdef CONFIG_DRM_AMD_DC_DSC_SUPPORT
-static enum dc_status add_dsc_to_stream_resource(struct dc *dc,
+enum dc_status dcn20_add_dsc_to_stream_resource(struct dc *dc,
 		struct dc_state *dc_ctx,
 		struct dc_stream_state *dc_stream)
 {
@@ -1460,6 +1460,9 @@ static enum dc_status add_dsc_to_stream_resource(struct dc *dc,
 		if (pipe_ctx->stream != dc_stream)
 			continue;
 
+		if (pipe_ctx->stream_res.dsc)
+			continue;
+
 		acquire_dsc(&dc_ctx->res_ctx, pool, &pipe_ctx->stream_res.dsc);
 
 		/* The number of DSCs can be less than the number of pipes */
@@ -1511,7 +1514,7 @@ enum dc_status dcn20_add_stream_to_ctx(struct dc *dc, struct dc_state *new_ctx,
 #ifdef CONFIG_DRM_AMD_DC_DSC_SUPPORT
 	/* Get a DSC if required and available */
 	if (result == DC_OK && dc_stream->timing.flags.DSC)
-		result = add_dsc_to_stream_resource(dc, new_ctx, dc_stream);
+		result = dcn20_add_dsc_to_stream_resource(dc, new_ctx, dc_stream);
 #endif
 
 	if (result == DC_OK)
diff --git a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.h b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.h
index 44f95aa0d61e..2209ebda6ef6 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.h
+++ b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.h
@@ -131,6 +131,7 @@ void dcn20_calculate_dlg_params(
 
 enum dc_status dcn20_build_mapped_resource(const struct dc *dc, struct dc_state *context, struct dc_stream_state *stream);
 enum dc_status dcn20_add_stream_to_ctx(struct dc *dc, struct dc_state *new_ctx, struct dc_stream_state *dc_stream);
+enum dc_status dcn20_add_dsc_to_stream_resource(struct dc *dc, struct dc_state *dc_ctx, struct dc_stream_state *dc_stream);
 enum dc_status dcn20_remove_stream_from_ctx(struct dc *dc, struct dc_state *new_ctx, struct dc_stream_state *dc_stream);
 enum dc_status dcn20_get_default_swizzle_mode(struct dc_plane_state *plane_state);
 
-- 
2.17.1

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[PATCH 15/15] drm/amd/display: Trigger modesets on MST DSC connectors

[mikita.lipski-5C7GfCeVMHo]

From: David Francis <David.Francis@amd.com>

Whenever a connector on an MST network is attached, detached, or
undergoes a modeset, the DSC configs for each stream on that
topology will be recalculated. This can change their required
bandwidth, requiring a full reprogramming, as though a modeset
was performed, even if that stream did not change timing.

Therefore, whenever a crtc has drm_atomic_crtc_needs_modeset,
for each crtc that shares a MST topology with that stream and
supports DSC, add that crtc (and all affected connectors and
planes) to the atomic state and set mode_changed on its state

v2: Do this check only on Navi and before adding connectors
and planes on modesetting crtcs

Cc: Leo Li <sunpeng.li@amd.com>
Cc: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Cc: Lyude Paul <lyude@redhat.com>
Signed-off-by: David Francis <David.Francis@amd.com>
---
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 79 +++++++++++++++++++
 1 file changed, 79 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index ba017e6bf0b4..f65326e85b86 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -6704,6 +6704,74 @@ static int do_aquire_global_lock(struct drm_device *dev,
 	return ret < 0 ? ret : 0;
 }
 
+#ifdef CONFIG_DRM_AMD_DC_DSC_SUPPORT
+/*
+ * TODO: This logic should at some point be moved into DRM
+ */
+static int add_affected_mst_dsc_crtcs(struct drm_atomic_state *state, struct drm_crtc *crtc)
+{
+	struct drm_connector *connector;
+	struct drm_connector_state *conn_state;
+	struct drm_connector_list_iter conn_iter;
+	struct drm_crtc_state *new_crtc_state;
+	struct amdgpu_dm_connector *aconnector = NULL, *aconnector_to_add;
+	int i, j;
+	struct drm_crtc *crtcs_affected[AMDGPU_MAX_CRTCS] = { 0 };
+
+	for_each_new_connector_in_state(state, connector, conn_state, i) {
+		if (conn_state->crtc != crtc)
+			continue;
+
+		aconnector = to_amdgpu_dm_connector(connector);
+		if (!aconnector->port)
+			aconnector = NULL;
+		else
+			break;
+	}
+
+	if (!aconnector)
+		return 0;
+
+	i = 0;
+	drm_connector_list_iter_begin(state->dev, &conn_iter);
+	drm_for_each_connector_iter(connector, &conn_iter) {
+		if (!connector->state || !connector->state->crtc)
+			continue;
+
+		aconnector_to_add = to_amdgpu_dm_connector(connector);
+		if (!aconnector_to_add->port)
+			continue;
+
+		if (aconnector_to_add->port->mgr != aconnector->port->mgr)
+			continue;
+
+		if (!aconnector_to_add->dc_sink)
+			continue;
+
+		if (!aconnector_to_add->dc_sink->sink_dsc_caps.dsc_dec_caps.is_dsc_supported)
+			continue;
+
+		if (i >= AMDGPU_MAX_CRTCS)
+			continue;
+
+		crtcs_affected[i] = connector->state->crtc;
+		i++;
+	}
+	drm_connector_list_iter_end(&conn_iter);
+
+	for (j = 0; j < i; j++) {
+		new_crtc_state = drm_atomic_get_crtc_state(state, crtcs_affected[j]);
+		if (IS_ERR(new_crtc_state))
+			return PTR_ERR(new_crtc_state);
+
+		new_crtc_state->mode_changed = true;
+	}
+
+	return 0;
+
+}
+#endif
+
 static void get_freesync_config_for_crtc(
 	struct dm_crtc_state *new_crtc_state,
 	struct dm_connector_state *new_con_state)
@@ -7388,6 +7456,17 @@ static int amdgpu_dm_atomic_check(struct drm_device *dev,
 	if (ret)
 		goto fail;
 
+#ifdef CONFIG_DRM_AMD_DC_DSC_SUPPORT
+	if (adev->asic_type >= CHIP_NAVI10) {
+		for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state, new_crtc_state, i) {
+			if (drm_atomic_crtc_needs_modeset(new_crtc_state)) {
+				ret = add_affected_mst_dsc_crtcs(state, crtc);
+				if (ret)
+					goto fail;
+			}
+		}
+	}
+#endif
 	for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state, new_crtc_state, i) {
 		if (!drm_atomic_crtc_needs_modeset(new_crtc_state) &&
 		    !new_crtc_state->color_mgmt_changed &&
-- 
2.17.1

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Re: [PATCH 15/15] drm/amd/display: Trigger modesets on MST DSC connectors

[Lyude Paul]

This still needs to be moved into an atomic helper so it can be reused by
other drivers
...
...

however, I've had this patch series on my mind for a while and something
occurred to me that would be a lot easier. Why exactly are we not just
enabling DSC wherever it's supported, regardless of whether or not it's
actually needed to fit into bandwidth constraints? The reason I mention this
is while only enabling DSC when needed makes perfect sense for SST, since I'd
assume non-DSC consumes less power, it doesn't quite make sense for MST.

See: currently with MST (at least this is the case with i915, but I plan on
making it the case with nouveau as well), we always default to link training
at the maximum link rate/lane count. i915 does the opposite with SST for
optimization, but we maximize for MST because maximizing the amount of
bandwidth we have to work with means that we can enable new displays and
disable displays without having to potentially update the rest of the topology
with new PBN/VCPI allocations (unless the bandwidth restrictions get lowered
later, of course).

An abstract example: Let's say a user has a hub setup with two displays,
without DSC enabled. The user plugs in a third display, but this display won't
fit into the available bandwidth without enabling DSC. But assuming enabling
DSC causes us to need to recalculate the bandwidth for the other two displays,
we end up having to do a modeset on all three displays.

Alternatively: the user has two displays again. This time though we started
off by using DSC from the start, so adding a new display can be done without
performing a modeset on the other two displays.

Taking this into consideration, wouldn't we be able to just get rid of this
whole function by enabling DSC by default instead of as-needed? And get a
nicer result?

On Wed, 2019-09-18 at 16:26 -0400, mikita.lipski@amd.com wrote:
> From: David Francis <David.Francis@amd.com>
> 
> Whenever a connector on an MST network is attached, detached, or
> undergoes a modeset, the DSC configs for each stream on that
> topology will be recalculated. This can change their required
> bandwidth, requiring a full reprogramming, as though a modeset
> was performed, even if that stream did not change timing.
> 
> Therefore, whenever a crtc has drm_atomic_crtc_needs_modeset,
> for each crtc that shares a MST topology with that stream and
> supports DSC, add that crtc (and all affected connectors and
> planes) to the atomic state and set mode_changed on its state
> 
> v2: Do this check only on Navi and before adding connectors
> and planes on modesetting crtcs
> 
> Cc: Leo Li <sunpeng.li@amd.com>
> Cc: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
> Cc: Lyude Paul <lyude@redhat.com>
> Signed-off-by: David Francis <David.Francis@amd.com>
> ---
>  .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 79 +++++++++++++++++++
>  1 file changed, 79 insertions(+)
> 
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index ba017e6bf0b4..f65326e85b86 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -6704,6 +6704,74 @@ static int do_aquire_global_lock(struct drm_device
> *dev,
>  	return ret < 0 ? ret : 0;
>  }
>  
> +#ifdef CONFIG_DRM_AMD_DC_DSC_SUPPORT
> +/*
> + * TODO: This logic should at some point be moved into DRM
> + */
> +static int add_affected_mst_dsc_crtcs(struct drm_atomic_state *state,
> struct drm_crtc *crtc)
> +{
> +	struct drm_connector *connector;
> +	struct drm_connector_state *conn_state;
> +	struct drm_connector_list_iter conn_iter;
> +	struct drm_crtc_state *new_crtc_state;
> +	struct amdgpu_dm_connector *aconnector = NULL, *aconnector_to_add;
> +	int i, j;
> +	struct drm_crtc *crtcs_affected[AMDGPU_MAX_CRTCS] = { 0 };
> +
> +	for_each_new_connector_in_state(state, connector, conn_state, i) {
> +		if (conn_state->crtc != crtc)
> +			continue;
> +
> +		aconnector = to_amdgpu_dm_connector(connector);
> +		if (!aconnector->port)
> +			aconnector = NULL;
> +		else
> +			break;
> +	}
> +
> +	if (!aconnector)
> +		return 0;
> +
> +	i = 0;
> +	drm_connector_list_iter_begin(state->dev, &conn_iter);
> +	drm_for_each_connector_iter(connector, &conn_iter) {
> +		if (!connector->state || !connector->state->crtc)
> +			continue;
> +
> +		aconnector_to_add = to_amdgpu_dm_connector(connector);
> +		if (!aconnector_to_add->port)
> +			continue;
> +
> +		if (aconnector_to_add->port->mgr != aconnector->port->mgr)
> +			continue;
> +
> +		if (!aconnector_to_add->dc_sink)
> +			continue;
> +
> +		if (!aconnector_to_add->dc_sink-
> >sink_dsc_caps.dsc_dec_caps.is_dsc_supported)
> +			continue;
> +
> +		if (i >= AMDGPU_MAX_CRTCS)
> +			continue;
> +
> +		crtcs_affected[i] = connector->state->crtc;
> +		i++;
> +	}
> +	drm_connector_list_iter_end(&conn_iter);
> +
> +	for (j = 0; j < i; j++) {
> +		new_crtc_state = drm_atomic_get_crtc_state(state,
> crtcs_affected[j]);
> +		if (IS_ERR(new_crtc_state))
> +			return PTR_ERR(new_crtc_state);
> +
> +		new_crtc_state->mode_changed = true;
> +	}
> +
> +	return 0;
> +
> +}
> +#endif
> +
>  static void get_freesync_config_for_crtc(
>  	struct dm_crtc_state *new_crtc_state,
>  	struct dm_connector_state *new_con_state)
> @@ -7388,6 +7456,17 @@ static int amdgpu_dm_atomic_check(struct drm_device
> *dev,
>  	if (ret)
>  		goto fail;
>  
> +#ifdef CONFIG_DRM_AMD_DC_DSC_SUPPORT
> +	if (adev->asic_type >= CHIP_NAVI10) {
> +		for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state,
> new_crtc_state, i) {
> +			if (drm_atomic_crtc_needs_modeset(new_crtc_state)) {
> +				ret = add_affected_mst_dsc_crtcs(state, crtc);
> +				if (ret)
> +					goto fail;
> +			}
> +		}
> +	}
> +#endif
>  	for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state,
> new_crtc_state, i) {
>  		if (!drm_atomic_crtc_needs_modeset(new_crtc_state) &&
>  		    !new_crtc_state->color_mgmt_changed &&
-- 
Cheers,
	Lyude Paul

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Re: [PATCH 15/15] drm/amd/display: Trigger modesets on MST DSC connectors

[Mikita Lipski]

On 19.09.2019 20:08, Lyude Paul wrote:
> This still needs to be moved into an atomic helper so it can be reused by
> other drivers

It would be a future to move the implementation to a contained atomic 
helper.

> ...
> ...
> 
> however, I've had this patch series on my mind for a while and something
> occurred to me that would be a lot easier. Why exactly are we not just
> enabling DSC wherever it's supported, regardless of whether or not it's
> actually needed to fit into bandwidth constraints? The reason I mention this
> is while only enabling DSC when needed makes perfect sense for SST, since I'd
> assume non-DSC consumes less power, it doesn't quite make sense for MST.
> 
> See: currently with MST (at least this is the case with i915, but I plan on
> making it the case with nouveau as well), we always default to link training
> at the maximum link rate/lane count. i915 does the opposite with SST for
> optimization, but we maximize for MST because maximizing the amount of
> bandwidth we have to work with means that we can enable new displays and
> disable displays without having to potentially update the rest of the topology
> with new PBN/VCPI allocations (unless the bandwidth restrictions get lowered
> later, of course).
> 
> An abstract example: Let's say a user has a hub setup with two displays,
> without DSC enabled. The user plugs in a third display, but this display won't
> fit into the available bandwidth without enabling DSC. But assuming enabling
> DSC causes us to need to recalculate the bandwidth for the other two displays,
> we end up having to do a modeset on all three displays.
> 
> Alternatively: the user has two displays again. This time though we started
> off by using DSC from the start, so adding a new display can be done without
> performing a modeset on the other two displays.
> 
> Taking this into consideration, wouldn't we be able to just get rid of this
> whole function by enabling DSC by default instead of as-needed? And get a
> nicer result?
The idea of enabling DSC from the beginning does sound appealing, but 
DSC is a lossy compression and we think it is better to enable it only 
when we need it, not to degrade picture quality. The greedy algorithm 
developed by David Francis in his patch "MST DSC compute fair share" 
tries to minimize compression and enable maximum number of streams 
without it, so they won't lose the picture quality.

That being said,  I agree, the implementation of DSC code would be much 
simpler if we would just enable DSC from the beginning, but again we do 
not want to compromise the picture quality.

> 
> On Wed, 2019-09-18 at 16:26 -0400, mikita.lipski@amd.com wrote:
>> From: David Francis <David.Francis@amd.com>
>>
>> Whenever a connector on an MST network is attached, detached, or
>> undergoes a modeset, the DSC configs for each stream on that
>> topology will be recalculated. This can change their required
>> bandwidth, requiring a full reprogramming, as though a modeset
>> was performed, even if that stream did not change timing.
>>
>> Therefore, whenever a crtc has drm_atomic_crtc_needs_modeset,
>> for each crtc that shares a MST topology with that stream and
>> supports DSC, add that crtc (and all affected connectors and
>> planes) to the atomic state and set mode_changed on its state
>>
>> v2: Do this check only on Navi and before adding connectors
>> and planes on modesetting crtcs
>>
>> Cc: Leo Li <sunpeng.li@amd.com>
>> Cc: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
>> Cc: Lyude Paul <lyude@redhat.com>
>> Signed-off-by: David Francis <David.Francis@amd.com>
>> ---
>>   .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 79 +++++++++++++++++++
>>   1 file changed, 79 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> index ba017e6bf0b4..f65326e85b86 100644
>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> @@ -6704,6 +6704,74 @@ static int do_aquire_global_lock(struct drm_device
>> *dev,
>>   	return ret < 0 ? ret : 0;
>>   }
>>   
>> +#ifdef CONFIG_DRM_AMD_DC_DSC_SUPPORT
>> +/*
>> + * TODO: This logic should at some point be moved into DRM
>> + */
>> +static int add_affected_mst_dsc_crtcs(struct drm_atomic_state *state,
>> struct drm_crtc *crtc)
>> +{
>> +	struct drm_connector *connector;
>> +	struct drm_connector_state *conn_state;
>> +	struct drm_connector_list_iter conn_iter;
>> +	struct drm_crtc_state *new_crtc_state;
>> +	struct amdgpu_dm_connector *aconnector = NULL, *aconnector_to_add;
>> +	int i, j;
>> +	struct drm_crtc *crtcs_affected[AMDGPU_MAX_CRTCS] = { 0 };
>> +
>> +	for_each_new_connector_in_state(state, connector, conn_state, i) {
>> +		if (conn_state->crtc != crtc)
>> +			continue;
>> +
>> +		aconnector = to_amdgpu_dm_connector(connector);
>> +		if (!aconnector->port)
>> +			aconnector = NULL;
>> +		else
>> +			break;
>> +	}
>> +
>> +	if (!aconnector)
>> +		return 0;
>> +
>> +	i = 0;
>> +	drm_connector_list_iter_begin(state->dev, &conn_iter);
>> +	drm_for_each_connector_iter(connector, &conn_iter) {
>> +		if (!connector->state || !connector->state->crtc)
>> +			continue;
>> +
>> +		aconnector_to_add = to_amdgpu_dm_connector(connector);
>> +		if (!aconnector_to_add->port)
>> +			continue;
>> +
>> +		if (aconnector_to_add->port->mgr != aconnector->port->mgr)
>> +			continue;
>> +
>> +		if (!aconnector_to_add->dc_sink)
>> +			continue;
>> +
>> +		if (!aconnector_to_add->dc_sink-
>>> sink_dsc_caps.dsc_dec_caps.is_dsc_supported)
>> +			continue;
>> +
>> +		if (i >= AMDGPU_MAX_CRTCS)
>> +			continue;
>> +
>> +		crtcs_affected[i] = connector->state->crtc;
>> +		i++;
>> +	}
>> +	drm_connector_list_iter_end(&conn_iter);
>> +
>> +	for (j = 0; j < i; j++) {
>> +		new_crtc_state = drm_atomic_get_crtc_state(state,
>> crtcs_affected[j]);
>> +		if (IS_ERR(new_crtc_state))
>> +			return PTR_ERR(new_crtc_state);
>> +
>> +		new_crtc_state->mode_changed = true;
>> +	}
>> +
>> +	return 0;
>> +
>> +}
>> +#endif
>> +
>>   static void get_freesync_config_for_crtc(
>>   	struct dm_crtc_state *new_crtc_state,
>>   	struct dm_connector_state *new_con_state)
>> @@ -7388,6 +7456,17 @@ static int amdgpu_dm_atomic_check(struct drm_device
>> *dev,
>>   	if (ret)
>>   		goto fail;
>>   
>> +#ifdef CONFIG_DRM_AMD_DC_DSC_SUPPORT
>> +	if (adev->asic_type >= CHIP_NAVI10) {
>> +		for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state,
>> new_crtc_state, i) {
>> +			if (drm_atomic_crtc_needs_modeset(new_crtc_state)) {
>> +				ret = add_affected_mst_dsc_crtcs(state, crtc);
>> +				if (ret)
>> +					goto fail;
>> +			}
>> +		}
>> +	}
>> +#endif
>>   	for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state,
>> new_crtc_state, i) {
>>   		if (!drm_atomic_crtc_needs_modeset(new_crtc_state) &&
>>   		    !new_crtc_state->color_mgmt_changed &&

-- 
Thanks,
Mikita Lipski
Software Engineer 2, AMD
mikita.lipski@amd.com
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