drm/i915/dp: Add support for DP tunnel BW allocation

Add support to enable the DP tunnel BW allocation mode. Follow-up
patches will call the required helpers added here to prepare for a
modeset on a link with DP tunnels, the last change in the patchset
actually enabling BWA.

With BWA enabled, the driver will expose the full mode list a display
supports, regardless of any BW limitation on a shared (Thunderbolt)
link. Such BW limits will be checked against only during a modeset, when
the driver has the full knowledge of each display's BW requirement.

If the link BW changes in a way that a connector's modelist may also
change, userspace will get a hotplug notification for all the connectors
sharing the same link (so it can adjust the mode used for a display).

The BW limitation can change at any point, asynchronously to modesets
on a given connector, so a modeset can fail even though the atomic check
for it passed. In such scenarios userspace will get a bad link
notification and in response is supposed to retry the modeset.

v2:
- Fix old vs. new connector state in intel_dp_tunnel_atomic_check_state().
  (Ville)
- Fix propagating the error from
  intel_dp_tunnel_atomic_compute_stream_bw(). (Ville)
- Move tunnel==NULL checks from driver to DRM core helpers. (Ville)
- Simplify return flow from intel_dp_tunnel_detect(). (Ville)
- s/dp_tunnel_state/inherited_dp_tunnels (Ville)
- Simplify struct intel_dp_tunnel_inherited_state. (Ville)
- Unconstify object pointers (vs. states) where possible. (Ville)
- Init crtc_state while declaring it in check_group_state(). (Ville)
- Join obj->base.id, obj->name arg lines in debug prints to reduce LOC.
  (Ville)
- Add/rework intel_dp_tunnel_atomic_alloc_bw() to prepare for moving the
  BW allocation from encoder hooks up to intel_atomic_commit_tail()
  later in the patchset.
- Disable BW alloc mode during system suspend.
- Allocate the required BW for all tunnels during system resume.
- Add intel_dp_tunnel_atomic_clear_stream_bw() instead of the open-coded
  sequence in a follow-up patch.
- Add function documentation to all exported functions.
- Add CONFIG_USB4 dependency to CONFIG_DRM_I915_DP_TUNNEL.

v3:
- Rebase on intel_dp_get_active_pipes() change in previous patch.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240226185246.1276018-4-imre.deak@intel.com

drivers/gpu/drm/i915/Kconfig

@@ -155,6 +155,20 @@ config DRM_I915_PXP
 	  protected session and manage the status of the alive software session,
 	  as well as its life cycle.
 
+config DRM_I915_DP_TUNNEL
+	bool "Enable DP tunnel support"
+	depends on DRM_I915
+	depends on USB4
+	select DRM_DISPLAY_DP_TUNNEL
+	default y
+	help
+	  Choose this option to detect DP tunnels and enable the Bandwidth
+	  Allocation mode for such tunnels. This allows using the maximum
+	  resolution allowed by the link BW on all displays sharing the
+	  link BW, for instance on a Thunderbolt link.
+
+	  If in doubt, say "Y".
+
 menu "drm/i915 Debugging"
 depends on DRM_I915
 depends on EXPERT

drivers/gpu/drm/i915/Kconfig.debug

@@ -28,6 +28,7 @@ config DRM_I915_DEBUG
 	select STACKDEPOT
 	select STACKTRACE
 	select DRM_DP_AUX_CHARDEV
+	select DRM_DISPLAY_DEBUG_DP_TUNNEL_STATE if DRM_I915_DP_TUNNEL
 	select X86_MSR # used by igt/pm_rpm
 	select DRM_VGEM # used by igt/prime_vgem (dmabuf interop checks)
 	select DRM_DEBUG_MM if DRM=y

drivers/gpu/drm/i915/Makefile

@@ -369,6 +369,9 @@ i915-y += \
 	display/vlv_dsi.o \
 	display/vlv_dsi_pll.o
 
+i915-$(CONFIG_DRM_I915_DP_TUNNEL) += \
+	display/intel_dp_tunnel.o
+
 i915-y += \
 	i915_perf.o
 

drivers/gpu/drm/i915/display/intel_atomic.c

@@ -29,6 +29,7 @@
  * See intel_atomic_plane.c for the plane-specific atomic functionality.
  */
 
+#include <drm/display/drm_dp_tunnel.h>
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_fourcc.h>
@@ -38,6 +39,7 @@
 #include "intel_atomic.h"
 #include "intel_cdclk.h"
 #include "intel_display_types.h"
+#include "intel_dp_tunnel.h"
 #include "intel_global_state.h"
 #include "intel_hdcp.h"
 #include "intel_psr.h"

drivers/gpu/drm/i915/display/intel_display_core.h

@@ -524,6 +524,7 @@ struct intel_display {
 	} wq;
 
 	/* Grouping using named structs. Keep sorted. */
+	struct drm_dp_tunnel_mgr *dp_tunnel_mgr;
 	struct intel_audio audio;
 	struct intel_dpll dpll;
 	struct intel_fbc *fbc[I915_MAX_FBCS];

drivers/gpu/drm/i915/display/intel_display_types.h

@@ -33,6 +33,7 @@
 
 #include <drm/display/drm_dp_dual_mode_helper.h>
 #include <drm/display/drm_dp_mst_helper.h>
+#include <drm/display/drm_dp_tunnel.h>
 #include <drm/display/drm_dsc.h>
 #include <drm/drm_atomic.h>
 #include <drm/drm_crtc.h>
@@ -682,6 +683,8 @@ struct intel_atomic_state {
 
 	struct intel_shared_dpll_state shared_dpll[I915_NUM_PLLS];
 
+	struct intel_dp_tunnel_inherited_state *inherited_dp_tunnels;
+
 	/*
 	 * Current watermarks can't be trusted during hardware readout, so
 	 * don't bother calculating intermediate watermarks.
@@ -1379,6 +1382,9 @@ struct intel_crtc_state {
 		struct drm_dsc_config config;
 	} dsc;
 
+	/* DP tunnel used for BW allocation. */
+	struct drm_dp_tunnel_ref dp_tunnel_ref;
+
 	/* HSW+ linetime watermarks */
 	u16 linetime;
 	u16 ips_linetime;
@@ -1789,6 +1795,9 @@ struct intel_dp {
 	/* connector directly attached - won't be use for modeset in mst world */
 	struct intel_connector *attached_connector;
 
+	struct drm_dp_tunnel *tunnel;
+	bool tunnel_suspended:1;
+
 	/* mst connector list */
 	struct intel_dp_mst_encoder *mst_encoders[I915_MAX_PIPES];
 	struct drm_dp_mst_topology_mgr mst_mgr;

drivers/gpu/drm/i915/display/intel_dp_tunnel.c

+// SPDX-License-Identifier: MIT
+/*
+ * Copyright © 2023 Intel Corporation
+ */
+
+#include "i915_drv.h"
+
+#include <drm/display/drm_dp_tunnel.h>
+
+#include "intel_atomic.h"
+#include "intel_display_limits.h"
+#include "intel_display_types.h"
+#include "intel_dp.h"
+#include "intel_dp_link_training.h"
+#include "intel_dp_mst.h"
+#include "intel_dp_tunnel.h"
+#include "intel_link_bw.h"
+
+struct intel_dp_tunnel_inherited_state {
+	struct drm_dp_tunnel_ref ref[I915_MAX_PIPES];
+};
+
+/**
+ * intel_dp_tunnel_disconnect - Disconnect a DP tunnel from a port
+ * @intel_dp: DP port object the tunnel is connected to
+ *
+ * Disconnect a DP tunnel from @intel_dp, destroying any related state. This
+ * should be called after detecting a sink-disconnect event from the port.
+ */
+void intel_dp_tunnel_disconnect(struct intel_dp *intel_dp)
+{
+	drm_dp_tunnel_destroy(intel_dp->tunnel);
+	intel_dp->tunnel = NULL;
+}
+
+/**
+ * intel_dp_tunnel_destroy - Destroy a DP tunnel
+ * @intel_dp: DP port object the tunnel is connected to
+ *
+ * Destroy a DP tunnel connected to @intel_dp, after disabling the BW
+ * allocation mode on the tunnel. This should be called while destroying the
+ * port.
+ */
+void intel_dp_tunnel_destroy(struct intel_dp *intel_dp)
+{
+	if (intel_dp_tunnel_bw_alloc_is_enabled(intel_dp))
+		drm_dp_tunnel_disable_bw_alloc(intel_dp->tunnel);
+
+	intel_dp_tunnel_disconnect(intel_dp);
+}
+
+static int kbytes_to_mbits(int kbytes)
+{
+	return DIV_ROUND_UP(kbytes * 8, 1000);
+}
+
+static int get_current_link_bw(struct intel_dp *intel_dp,
+			       bool *below_dprx_bw)
+{
+	int rate = intel_dp_max_common_rate(intel_dp);
+	int lane_count = intel_dp_max_common_lane_count(intel_dp);
+	int bw;
+
+	bw = intel_dp_max_link_data_rate(intel_dp, rate, lane_count);
+	*below_dprx_bw = bw < drm_dp_max_dprx_data_rate(rate, lane_count);
+
+	return bw;
+}
+
+static int update_tunnel_state(struct intel_dp *intel_dp)
+{
+	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
+	struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;
+	bool old_bw_below_dprx;
+	bool new_bw_below_dprx;
+	int old_bw;
+	int new_bw;
+	int ret;
+
+	old_bw = get_current_link_bw(intel_dp, &old_bw_below_dprx);
+
+	ret = drm_dp_tunnel_update_state(intel_dp->tunnel);
+	if (ret < 0) {
+		drm_dbg_kms(&i915->drm,
+			    "[DPTUN %s][ENCODER:%d:%s] State update failed (err %pe)\n",
+			    drm_dp_tunnel_name(intel_dp->tunnel),
+			    encoder->base.base.id, encoder->base.name,
+			    ERR_PTR(ret));
+
+		return ret;
+	}
+
+	if (ret == 0 ||
+	    !drm_dp_tunnel_bw_alloc_is_enabled(intel_dp->tunnel))
+		return 0;
+
+	intel_dp_update_sink_caps(intel_dp);
+
+	new_bw = get_current_link_bw(intel_dp, &new_bw_below_dprx);
+
+	/* Suppress the notification if the mode list can't change due to bw. */
+	if (old_bw_below_dprx == new_bw_below_dprx &&
+	    !new_bw_below_dprx)
+		return 0;
+
+	drm_dbg_kms(&i915->drm,
+		    "[DPTUN %s][ENCODER:%d:%s] Notify users about BW change: %d -> %d\n",
+		    drm_dp_tunnel_name(intel_dp->tunnel),
+		    encoder->base.base.id, encoder->base.name,
+		    kbytes_to_mbits(old_bw), kbytes_to_mbits(new_bw));
+
+	return 1;
+}
+
+/*
+ * Allocate the BW for a tunnel on a DP connector/port if the connector/port
+ * was already active when detecting the tunnel. The allocated BW must be
+ * freed by the next atomic modeset, storing the BW in the
+ * intel_atomic_state::inherited_dp_tunnels, and calling
+ * intel_dp_tunnel_atomic_free_bw().
+ */
+static int allocate_initial_tunnel_bw_for_pipes(struct intel_dp *intel_dp, u8 pipe_mask)
+{
+	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
+	struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;
+	struct intel_crtc *crtc;
+	int tunnel_bw = 0;
+	int err;
+
+	for_each_intel_crtc_in_pipe_mask(&i915->drm, crtc, pipe_mask) {
+		const struct intel_crtc_state *crtc_state =
+			to_intel_crtc_state(crtc->base.state);
+		int stream_bw = intel_dp_config_required_rate(crtc_state);
+
+		tunnel_bw += stream_bw;
+
+		drm_dbg_kms(&i915->drm,
+			    "[DPTUN %s][ENCODER:%d:%s][CRTC:%d:%s] Initial BW for stream %d: %d/%d Mb/s\n",
+			    drm_dp_tunnel_name(intel_dp->tunnel),
+			    encoder->base.base.id, encoder->base.name,
+			    crtc->base.base.id, crtc->base.name,
+			    crtc->pipe,
+			    kbytes_to_mbits(stream_bw), kbytes_to_mbits(tunnel_bw));
+	}
+
+	err = drm_dp_tunnel_alloc_bw(intel_dp->tunnel, tunnel_bw);
+	if (err) {
+		drm_dbg_kms(&i915->drm,
+			    "[DPTUN %s][ENCODER:%d:%s] Initial BW allocation failed (err %pe)\n",
+			    drm_dp_tunnel_name(intel_dp->tunnel),
+			    encoder->base.base.id, encoder->base.name,
+			    ERR_PTR(err));
+
+		return err;
+	}
+
+	return update_tunnel_state(intel_dp);
+}
+
+static int allocate_initial_tunnel_bw(struct intel_dp *intel_dp,
+				      struct drm_modeset_acquire_ctx *ctx)
+{
+	u8 pipe_mask;
+	int err;
+
+	err = intel_dp_get_active_pipes(intel_dp, ctx, &pipe_mask);
+	if (err)
+		return err;
+
+	return allocate_initial_tunnel_bw_for_pipes(intel_dp, pipe_mask);
+}
+
+static int detect_new_tunnel(struct intel_dp *intel_dp, struct drm_modeset_acquire_ctx *ctx)
+{
+	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
+	struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;
+	struct drm_dp_tunnel *tunnel;
+	int ret;
+
+	tunnel = drm_dp_tunnel_detect(i915->display.dp_tunnel_mgr,
+				      &intel_dp->aux);
+	if (IS_ERR(tunnel))
+		return PTR_ERR(tunnel);
+
+	intel_dp->tunnel = tunnel;
+
+	ret = drm_dp_tunnel_enable_bw_alloc(intel_dp->tunnel);
+	if (ret) {
+		if (ret == -EOPNOTSUPP)
+			return 0;
+
+		drm_dbg_kms(&i915->drm,
+			    "[DPTUN %s][ENCODER:%d:%s] Failed to enable BW allocation mode (ret %pe)\n",
+			    drm_dp_tunnel_name(intel_dp->tunnel),
+			    encoder->base.base.id, encoder->base.name,
+			    ERR_PTR(ret));
+
+		/* Keep the tunnel with BWA disabled */
+		return 0;
+	}
+
+	ret = allocate_initial_tunnel_bw(intel_dp, ctx);
+	if (ret < 0)
+		intel_dp_tunnel_destroy(intel_dp);
+
+	return ret;
+}
+
+/**
+ * intel_dp_tunnel_detect - Detect a DP tunnel on a port
+ * @intel_dp: DP port object
+ * @ctx: lock context acquired by the connector detection handler
+ *
+ * Detect a DP tunnel on the @intel_dp port, enabling the BW allocation mode
+ * on it if supported and allocating the BW required on an already active port.
+ * The BW allocated this way must be freed by the next atomic modeset calling
+ * intel_dp_tunnel_atomic_free_bw().
+ *
+ * If @intel_dp has already a tunnel detected on it, update the tunnel's state
+ * wrt. its support for BW allocation mode and the available BW via the
+ * tunnel. If the tunnel's state change requires this - for instance the
+ * tunnel's group ID has changed - the tunnel will be dropped and recreated.
+ *
+ * Return 0 in case of success - after any tunnel detected and added to
+ * @intel_dp - 1 in case the BW on an already existing tunnel has changed in a
+ * way that requires notifying user space.
+ */
+int intel_dp_tunnel_detect(struct intel_dp *intel_dp, struct drm_modeset_acquire_ctx *ctx)
+{
+	int ret;
+
+	if (intel_dp_is_edp(intel_dp))
+		return 0;
+
+	if (intel_dp->tunnel) {
+		ret = update_tunnel_state(intel_dp);
+		if (ret >= 0)
+			return ret;
+
+		/* Try to recreate the tunnel after an update error. */
+		intel_dp_tunnel_destroy(intel_dp);
+	}
+
+	return detect_new_tunnel(intel_dp, ctx);
+}
+
+/**
+ * intel_dp_tunnel_bw_alloc_is_enabled - Query the BW allocation support on a tunnel
+ * @intel_dp: DP port object
+ *
+ * Query whether a DP tunnel is connected on @intel_dp and the tunnel supports
+ * the BW allocation mode.
+ *
+ * Returns %true if the BW allocation mode is supported on @intel_dp.
+ */
+bool intel_dp_tunnel_bw_alloc_is_enabled(struct intel_dp *intel_dp)
+{
+	return drm_dp_tunnel_bw_alloc_is_enabled(intel_dp->tunnel);
+}
+
+/**
+ * intel_dp_tunnel_suspend - Suspend a DP tunnel connected on a port
+ * @intel_dp: DP port object
+ *
+ * Suspend a DP tunnel on @intel_dp with BW allocation mode enabled on it.
+ */
+void intel_dp_tunnel_suspend(struct intel_dp *intel_dp)
+{
+	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
+	struct intel_connector *connector = intel_dp->attached_connector;
+	struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;
+
+	if (!intel_dp_tunnel_bw_alloc_is_enabled(intel_dp))
+		return;
+
+	drm_dbg_kms(&i915->drm, "[DPTUN %s][CONNECTOR:%d:%s][ENCODER:%d:%s] Suspend\n",
+		    drm_dp_tunnel_name(intel_dp->tunnel),
+		    connector->base.base.id, connector->base.name,
+		    encoder->base.base.id, encoder->base.name);
+
+	drm_dp_tunnel_disable_bw_alloc(intel_dp->tunnel);
+
+	intel_dp->tunnel_suspended = true;
+}
+
+/**
+ * intel_dp_tunnel_resume - Resume a DP tunnel connected on a port
+ * @intel_dp: DP port object
+ * @crtc_state: CRTC state
+ * @dpcd_updated: the DPCD DPRX capabilities got updated during resume
+ *
+ * Resume a DP tunnel on @intel_dp with BW allocation mode enabled on it.
+ */
+void intel_dp_tunnel_resume(struct intel_dp *intel_dp,
+			    const struct intel_crtc_state *crtc_state,
+			    bool dpcd_updated)
+{
+	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
+	struct intel_connector *connector = intel_dp->attached_connector;
+	struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;
+	u8 dpcd[DP_RECEIVER_CAP_SIZE];
+	u8 pipe_mask;
+	int err = 0;
+
+	if (!intel_dp->tunnel_suspended)
+		return;
+
+	intel_dp->tunnel_suspended = false;
+
+	drm_dbg_kms(&i915->drm, "[DPTUN %s][CONNECTOR:%d:%s][ENCODER:%d:%s] Resume\n",
+		    drm_dp_tunnel_name(intel_dp->tunnel),
+		    connector->base.base.id, connector->base.name,
+		    encoder->base.base.id, encoder->base.name);
+
+	/*
+	 * The TBT Connection Manager requires the GFX driver to read out
+	 * the sink's DPRX caps to be able to service any BW requests later.
+	 * During resume overriding the caps in @intel_dp cached before
+	 * suspend must be avoided, so do here only a dummy read, unless the
+	 * capabilities were updated already during resume.
+	 */
+	if (!dpcd_updated) {
+		err = intel_dp_read_dprx_caps(intel_dp, dpcd);
+
+		if (err) {
+			drm_dp_tunnel_set_io_error(intel_dp->tunnel);
+			goto out_err;
+		}
+	}
+
+	err = drm_dp_tunnel_enable_bw_alloc(intel_dp->tunnel);
+	if (err)
+		goto out_err;
+
+	pipe_mask = 0;
+	if (crtc_state) {
+		struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
+
+		/* TODO: Add support for MST */
+		pipe_mask |= BIT(crtc->pipe);
+	}
+
+	err = allocate_initial_tunnel_bw_for_pipes(intel_dp, pipe_mask);
+	if (err < 0)
+		goto out_err;
+
+	return;
+
+out_err:
+	drm_dbg_kms(&i915->drm,
+		    "[DPTUN %s][CONNECTOR:%d:%s][ENCODER:%d:%s] Tunnel can't be resumed, will drop and redect it (err %pe)\n",
+		    drm_dp_tunnel_name(intel_dp->tunnel),
+		    connector->base.base.id, connector->base.name,
+		    encoder->base.base.id, encoder->base.name,
+		    ERR_PTR(err));
+}
+
+static struct drm_dp_tunnel *
+get_inherited_tunnel(struct intel_atomic_state *state, struct intel_crtc *crtc)
+{
+	if (!state->inherited_dp_tunnels)
+		return NULL;
+
+	return state->inherited_dp_tunnels->ref[crtc->pipe].tunnel;
+}
+
+static int
+add_inherited_tunnel(struct intel_atomic_state *state,
+		     struct drm_dp_tunnel *tunnel,
+		     struct intel_crtc *crtc)
+{
+	struct drm_i915_private *i915 = to_i915(state->base.dev);
+	struct drm_dp_tunnel *old_tunnel;
+
+	old_tunnel = get_inherited_tunnel(state, crtc);
+	if (old_tunnel) {
+		drm_WARN_ON(&i915->drm, old_tunnel != tunnel);
+		return 0;
+	}
+
+	if (!state->inherited_dp_tunnels) {
+		state->inherited_dp_tunnels = kzalloc(sizeof(*state->inherited_dp_tunnels),
+						      GFP_KERNEL);
+		if (!state->inherited_dp_tunnels)
+			return -ENOMEM;
+	}
+
+	drm_dp_tunnel_ref_get(tunnel, &state->inherited_dp_tunnels->ref[crtc->pipe]);
+
+	return 0;
+}
+
+static int check_inherited_tunnel_state(struct intel_atomic_state *state,
+					struct intel_dp *intel_dp,
+					const struct intel_digital_connector_state *old_conn_state)
+{
+	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
+	struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;
+	struct intel_connector *connector =
+		to_intel_connector(old_conn_state->base.connector);
+	struct intel_crtc *old_crtc;
+	const struct intel_crtc_state *old_crtc_state;
+
+	/*
+	 * If a BWA tunnel gets detected only after the corresponding
+	 * connector got enabled already without a BWA tunnel, or a different
+	 * BWA tunnel (which was removed meanwhile) the old CRTC state won't
+	 * contain the state of the current tunnel. This tunnel still has a
+	 * reserved BW, which needs to be released, add the state for such
+	 * inherited tunnels separately only to this atomic state.
+	 */
+	if (!intel_dp_tunnel_bw_alloc_is_enabled(intel_dp))
+		return 0;
+
+	if (!old_conn_state->base.crtc)
+		return 0;
+
+	old_crtc = to_intel_crtc(old_conn_state->base.crtc);
+	old_crtc_state = intel_atomic_get_old_crtc_state(state, old_crtc);
+
+	if (!old_crtc_state->hw.active ||
+	    old_crtc_state->dp_tunnel_ref.tunnel == intel_dp->tunnel)
+		return 0;
+
+	drm_dbg_kms(&i915->drm,
+		    "[DPTUN %s][CONNECTOR:%d:%s][ENCODER:%d:%s][CRTC:%d:%s] Adding state for inherited tunnel %p\n",
+		    drm_dp_tunnel_name(intel_dp->tunnel),
+		    connector->base.base.id, connector->base.name,
+		    encoder->base.base.id, encoder->base.name,
+		    old_crtc->base.base.id, old_crtc->base.name,
+		    intel_dp->tunnel);
+
+	return add_inherited_tunnel(state, intel_dp->tunnel, old_crtc);
+}
+
+/**
+ * intel_dp_tunnel_atomic_cleanup_inherited_state - Free any inherited DP tunnel state
+ * @state: Atomic state
+ *
+ * Free the inherited DP tunnel state in @state.
+ */
+void intel_dp_tunnel_atomic_cleanup_inherited_state(struct intel_atomic_state *state)
+{
+	enum pipe pipe;
+
+	if (!state->inherited_dp_tunnels)
+		return;
+
+	for_each_pipe(to_i915(state->base.dev), pipe)
+		if (state->inherited_dp_tunnels->ref[pipe].tunnel)
+			drm_dp_tunnel_ref_put(&state->inherited_dp_tunnels->ref[pipe]);
+
+	kfree(state->inherited_dp_tunnels);
+	state->inherited_dp_tunnels = NULL;
+}
+
+static int intel_dp_tunnel_atomic_add_group_state(struct intel_atomic_state *state,
+						  struct drm_dp_tunnel *tunnel)
+{
+	struct drm_i915_private *i915 = to_i915(state->base.dev);
+	u32 pipe_mask;
+	int err;
+
+	err = drm_dp_tunnel_atomic_get_group_streams_in_state(&state->base,
+							      tunnel, &pipe_mask);
+	if (err)
+		return err;
+
+	drm_WARN_ON(&i915->drm, pipe_mask & ~((1 << I915_MAX_PIPES) - 1));
+
+	return intel_modeset_pipes_in_mask_early(state, "DPTUN", pipe_mask);
+}
+
+/**
+ * intel_dp_tunnel_atomic_add_state_for_crtc - Add CRTC specific DP tunnel state
+ * @state: Atomic state
+ * @crtc: CRTC to add the tunnel state for
+ *
+ * Add the DP tunnel state for @crtc if the CRTC (aka DP tunnel stream) is enabled
+ * via a DP tunnel.
+ *
+ * Return 0 in case of success, a negative error code otherwise.
+ */
+int intel_dp_tunnel_atomic_add_state_for_crtc(struct intel_atomic_state *state,
+					      struct intel_crtc *crtc)
+{
+	const struct intel_crtc_state *new_crtc_state =
+		intel_atomic_get_new_crtc_state(state, crtc);
+	const struct drm_dp_tunnel_state *tunnel_state;
+	struct drm_dp_tunnel *tunnel = new_crtc_state->dp_tunnel_ref.tunnel;
+
+	if (!tunnel)
+		return 0;
+
+	tunnel_state = drm_dp_tunnel_atomic_get_state(&state->base, tunnel);
+	if (IS_ERR(tunnel_state))
+		return PTR_ERR(tunnel_state);
+
+	return 0;
+}
+
+static int check_group_state(struct intel_atomic_state *state,
+			     struct intel_dp *intel_dp,
+			     struct intel_connector *connector,
+			     struct intel_crtc *crtc)
+{
+	struct drm_i915_private *i915 = to_i915(state->base.dev);
+	struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;
+	const struct intel_crtc_state *crtc_state =
+		intel_atomic_get_new_crtc_state(state, crtc);
+
+	if (!crtc_state->dp_tunnel_ref.tunnel)
+		return 0;
+
+	drm_dbg_kms(&i915->drm,
+		    "[DPTUN %s][CONNECTOR:%d:%s][ENCODER:%d:%s][CRTC:%d:%s] Adding group state for tunnel %p\n",
+		    drm_dp_tunnel_name(intel_dp->tunnel),
+		    connector->base.base.id, connector->base.name,
+		    encoder->base.base.id, encoder->base.name,
+		    crtc->base.base.id, crtc->base.name,
+		    crtc_state->dp_tunnel_ref.tunnel);
+
+	return intel_dp_tunnel_atomic_add_group_state(state, crtc_state->dp_tunnel_ref.tunnel);
+}
+
+/**
+ * intel_dp_tunnel_atomic_check_state - Check a connector's DP tunnel specific state
+ * @state: Atomic state
+ * @intel_dp: DP port object
+ * @connector: connector using @intel_dp
+ *
+ * Check and add the DP tunnel atomic state for @intel_dp/@connector to
+ * @state, if there is a DP tunnel detected on @intel_dp with BW allocation
+ * mode enabled on it, or if @intel_dp/@connector was previously enabled via a
+ * DP tunnel.
+ *
+ * Returns 0 in case of success, or a negative error code otherwise.
+ */
+int intel_dp_tunnel_atomic_check_state(struct intel_atomic_state *state,
+				       struct intel_dp *intel_dp,
+				       struct intel_connector *connector)
+{
+	const struct intel_digital_connector_state *old_conn_state =
+		intel_atomic_get_old_connector_state(state, connector);
+	const struct intel_digital_connector_state *new_conn_state =
+		intel_atomic_get_new_connector_state(state, connector);
+	int err;
+
+	if (old_conn_state->base.crtc) {
+		err = check_group_state(state, intel_dp, connector,
+					to_intel_crtc(old_conn_state->base.crtc));
+		if (err)
+			return err;
+	}
+
+	if (new_conn_state->base.crtc &&
+	    new_conn_state->base.crtc != old_conn_state->base.crtc) {
+		err = check_group_state(state, intel_dp, connector,
+					to_intel_crtc(new_conn_state->base.crtc));
+		if (err)
+			return err;
+	}
+
+	return check_inherited_tunnel_state(state, intel_dp, old_conn_state);
+}
+
+/**
+ * intel_dp_tunnel_atomic_compute_stream_bw - Compute the BW required by a DP tunnel stream
+ * @state: Atomic state
+ * @intel_dp: DP object
+ * @connector: connector using @intel_dp
+ * @crtc_state: state of CRTC of the given DP tunnel stream
+ *
+ * Compute the required BW of CRTC (aka DP tunnel stream), storing this BW to
+ * the DP tunnel state containing the stream in @state. Before re-calculating a
+ * BW requirement in the crtc_state state the old BW requirement computed by this
+ * function must be cleared by calling intel_dp_tunnel_atomic_clear_stream_bw().
+ *
+ * Returns 0 in case of success, a negative error code otherwise.
+ */
+int intel_dp_tunnel_atomic_compute_stream_bw(struct intel_atomic_state *state,
+					     struct intel_dp *intel_dp,
+					     const struct intel_connector *connector,
+					     struct intel_crtc_state *crtc_state)
+{
+	struct drm_i915_private *i915 = to_i915(state->base.dev);
+	struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;
+	struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
+	int required_rate = intel_dp_config_required_rate(crtc_state);
+	int ret;
+
+	if (!intel_dp_tunnel_bw_alloc_is_enabled(intel_dp))
+		return 0;
+
+	drm_dbg_kms(&i915->drm,
+		    "[DPTUN %s][CONNECTOR:%d:%s][ENCODER:%d:%s][CRTC:%d:%s] Stream %d required BW %d Mb/s\n",
+		    drm_dp_tunnel_name(intel_dp->tunnel),
+		    connector->base.base.id, connector->base.name,
+		    encoder->base.base.id, encoder->base.name,
+		    crtc->base.base.id, crtc->base.name,
+		    crtc->pipe,
+		    kbytes_to_mbits(required_rate));
+
+	ret = drm_dp_tunnel_atomic_set_stream_bw(&state->base, intel_dp->tunnel,
+						 crtc->pipe, required_rate);
+	if (ret < 0)
+		return ret;
+
+	drm_dp_tunnel_ref_get(intel_dp->tunnel,
+			      &crtc_state->dp_tunnel_ref);
+
+	return 0;
+}
+
+/**
+ * intel_dp_tunnel_atomic_clear_stream_bw - Clear any DP tunnel stream BW requirement
+ * @state: Atomic state
+ * @crtc_state: state of CRTC of the given DP tunnel stream
+ *
+ * Clear any DP tunnel stream BW requirement set by
+ * intel_dp_tunnel_atomic_compute_stream_bw().
+ */
+void intel_dp_tunnel_atomic_clear_stream_bw(struct intel_atomic_state *state,
+					    struct intel_crtc_state *crtc_state)
+{
+	struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
+
+	if (!crtc_state->dp_tunnel_ref.tunnel)
+		return;
+
+	drm_dp_tunnel_atomic_set_stream_bw(&state->base,
+					   crtc_state->dp_tunnel_ref.tunnel,
+					   crtc->pipe, 0);
+	drm_dp_tunnel_ref_put(&crtc_state->dp_tunnel_ref);
+}
+
+/**
+ * intel_dp_tunnel_atomic_check_link - Check the DP tunnel atomic state
+ * @state: intel atomic state
+ * @limits: link BW limits
+ *
+ * Check the link configuration for all DP tunnels in @state. If the
+ * configuration is invalid @limits will be updated if possible to
+ * reduce the total BW, after which the configuration for all CRTCs in
+ * @state must be recomputed with the updated @limits.
+ *
+ * Returns:
+ *   - 0 if the confugration is valid
+ *   - %-EAGAIN, if the configuration is invalid and @limits got updated
+ *     with fallback values with which the configuration of all CRTCs in
+ *     @state must be recomputed
+ *   - Other negative error, if the configuration is invalid without a
+ *     fallback possibility, or the check failed for another reason
+ */
+int intel_dp_tunnel_atomic_check_link(struct intel_atomic_state *state,
+				      struct intel_link_bw_limits *limits)
+{
+	u32 failed_stream_mask;
+	int err;
+
+	err = drm_dp_tunnel_atomic_check_stream_bws(&state->base,
+						    &failed_stream_mask);
+	if (err != -ENOSPC)
+		return err;
+
+	err = intel_link_bw_reduce_bpp(state, limits,
+				       failed_stream_mask, "DP tunnel link BW");
+
+	return err ? : -EAGAIN;
+}
+
+static void atomic_decrease_bw(struct intel_atomic_state *state)
+{
+	struct intel_crtc *crtc;
+	const struct intel_crtc_state *old_crtc_state;
+	const struct intel_crtc_state *new_crtc_state;
+	int i;
+
+	for_each_oldnew_intel_crtc_in_state(state, crtc, old_crtc_state, new_crtc_state, i) {
+		const struct drm_dp_tunnel_state *new_tunnel_state;
+		struct drm_dp_tunnel *tunnel;
+		int old_bw;
+		int new_bw;
+
+		if (!intel_crtc_needs_modeset(new_crtc_state))
+			continue;
+
+		tunnel = get_inherited_tunnel(state, crtc);
+		if (!tunnel)
+			tunnel = old_crtc_state->dp_tunnel_ref.tunnel;
+
+		if (!tunnel)
+			continue;
+
+		old_bw = drm_dp_tunnel_get_allocated_bw(tunnel);
+
+		new_tunnel_state = drm_dp_tunnel_atomic_get_new_state(&state->base, tunnel);
+		new_bw = drm_dp_tunnel_atomic_get_required_bw(new_tunnel_state);
+
+		if (new_bw >= old_bw)
+			continue;
+
+		drm_dp_tunnel_alloc_bw(tunnel, new_bw);
+	}
+}
+
+static void queue_retry_work(struct intel_atomic_state *state,
+			     struct drm_dp_tunnel *tunnel,
+			     const struct intel_crtc_state *crtc_state)
+{
+	struct drm_i915_private *i915 = to_i915(state->base.dev);
+	struct intel_encoder *encoder;
+
+	encoder = intel_get_crtc_new_encoder(state, crtc_state);
+
+	if (!intel_digital_port_connected(encoder))
+		return;
+
+	drm_dbg_kms(&i915->drm,
+		    "[DPTUN %s][ENCODER:%d:%s] BW allocation failed on a connected sink\n",
+		    drm_dp_tunnel_name(tunnel),
+		    encoder->base.base.id,
+		    encoder->base.name);
+
+	intel_dp_queue_modeset_retry_for_link(state, encoder, crtc_state);
+}
+
+static void atomic_increase_bw(struct intel_atomic_state *state)
+{
+	struct intel_crtc *crtc;
+	const struct intel_crtc_state *crtc_state;
+	int i;
+
+	for_each_new_intel_crtc_in_state(state, crtc, crtc_state, i) {
+		struct drm_dp_tunnel_state *tunnel_state;
+		struct drm_dp_tunnel *tunnel = crtc_state->dp_tunnel_ref.tunnel;
+		int bw;
+
+		if (!intel_crtc_needs_modeset(crtc_state))
+			continue;
+
+		if (!tunnel)
+			continue;
+
+		tunnel_state = drm_dp_tunnel_atomic_get_new_state(&state->base, tunnel);
+
+		bw = drm_dp_tunnel_atomic_get_required_bw(tunnel_state);
+
+		if (drm_dp_tunnel_alloc_bw(tunnel, bw) != 0)
+			queue_retry_work(state, tunnel, crtc_state);
+	}
+}
+
+/**
+ * intel_dp_tunnel_atomic_alloc_bw - Allocate the BW for all modeset tunnels
+ * @state: Atomic state
+ *
+ * Allocate the required BW for all tunnels in @state.
+ */
+void intel_dp_tunnel_atomic_alloc_bw(struct intel_atomic_state *state)
+{
+	atomic_decrease_bw(state);
+	atomic_increase_bw(state);
+}
+
+/**
+ * intel_dp_tunnel_mgr_init - Initialize the DP tunnel manager
+ * @i915: i915 device object
+ *
+ * Initialize the DP tunnel manager. The tunnel manager will support the
+ * detection/management of DP tunnels on all DP connectors, so the function
+ * must be called after all these connectors have been registered already.
+ *
+ * Return 0 in case of success, a negative error code otherwise.
+ */
+int intel_dp_tunnel_mgr_init(struct drm_i915_private *i915)
+{
+	struct drm_dp_tunnel_mgr *tunnel_mgr;
+	struct drm_connector_list_iter connector_list_iter;
+	struct intel_connector *connector;
+	int dp_connectors = 0;
+
+	drm_connector_list_iter_begin(&i915->drm, &connector_list_iter);
+	for_each_intel_connector_iter(connector, &connector_list_iter) {
+		if (connector->base.connector_type != DRM_MODE_CONNECTOR_DisplayPort)
+			continue;
+
+		dp_connectors++;
+	}
+	drm_connector_list_iter_end(&connector_list_iter);
+
+	tunnel_mgr = drm_dp_tunnel_mgr_create(&i915->drm, dp_connectors);
+	if (IS_ERR(tunnel_mgr))
+		return PTR_ERR(tunnel_mgr);
+
+	i915->display.dp_tunnel_mgr = tunnel_mgr;
+
+	return 0;
+}
+
+/**
+ * intel_dp_tunnel_mgr_cleanup - Clean up the DP tunnel manager state
+ * @i915: i915 device object
+ *
+ * Clean up the DP tunnel manager state.
+ */
+void intel_dp_tunnel_mgr_cleanup(struct drm_i915_private *i915)
+{
+	drm_dp_tunnel_mgr_destroy(i915->display.dp_tunnel_mgr);
+	i915->display.dp_tunnel_mgr = NULL;
+}

drivers/gpu/drm/i915/display/intel_dp_tunnel.h

+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2023 Intel Corporation
+ */
+
+#ifndef __INTEL_DP_TUNNEL_H__
+#define __INTEL_DP_TUNNEL_H__
+
+#include <linux/errno.h>
+#include <linux/types.h>
+
+struct drm_i915_private;
+struct drm_connector_state;
+struct drm_modeset_acquire_ctx;
+
+struct intel_atomic_state;
+struct intel_connector;
+struct intel_crtc;
+struct intel_crtc_state;
+struct intel_dp;
+struct intel_encoder;
+struct intel_link_bw_limits;
+
+#if defined(CONFIG_DRM_I915_DP_TUNNEL) && defined(I915)
+
+int intel_dp_tunnel_detect(struct intel_dp *intel_dp, struct drm_modeset_acquire_ctx *ctx);
+void intel_dp_tunnel_disconnect(struct intel_dp *intel_dp);
+void intel_dp_tunnel_destroy(struct intel_dp *intel_dp);
+void intel_dp_tunnel_resume(struct intel_dp *intel_dp,
+			    const struct intel_crtc_state *crtc_state,
+			    bool dpcd_updated);
+void intel_dp_tunnel_suspend(struct intel_dp *intel_dp);
+
+bool intel_dp_tunnel_bw_alloc_is_enabled(struct intel_dp *intel_dp);
+
+void
+intel_dp_tunnel_atomic_cleanup_inherited_state(struct intel_atomic_state *state);
+
+int intel_dp_tunnel_atomic_compute_stream_bw(struct intel_atomic_state *state,
+					     struct intel_dp *intel_dp,
+					     const struct intel_connector *connector,
+					     struct intel_crtc_state *crtc_state);
+void intel_dp_tunnel_atomic_clear_stream_bw(struct intel_atomic_state *state,
+					    struct intel_crtc_state *crtc_state);
+
+int intel_dp_tunnel_atomic_add_state_for_crtc(struct intel_atomic_state *state,
+					      struct intel_crtc *crtc);
+int intel_dp_tunnel_atomic_check_link(struct intel_atomic_state *state,
+				      struct intel_link_bw_limits *limits);
+int intel_dp_tunnel_atomic_check_state(struct intel_atomic_state *state,
+				       struct intel_dp *intel_dp,
+				       struct intel_connector *connector);
+
+void intel_dp_tunnel_atomic_alloc_bw(struct intel_atomic_state *state);
+
+int intel_dp_tunnel_mgr_init(struct drm_i915_private *i915);
+void intel_dp_tunnel_mgr_cleanup(struct drm_i915_private *i915);
+
+#else
+
+static inline int
+intel_dp_tunnel_detect(struct intel_dp *intel_dp, struct drm_modeset_acquire_ctx *ctx)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline void intel_dp_tunnel_disconnect(struct intel_dp *intel_dp) {}
+static inline void intel_dp_tunnel_destroy(struct intel_dp *intel_dp) {}
+static inline void intel_dp_tunnel_resume(struct intel_dp *intel_dp,
+					  const struct intel_crtc_state *crtc_state,
+					  bool dpcd_updated) {}
+static inline void intel_dp_tunnel_suspend(struct intel_dp *intel_dp) {}
+
+static inline bool intel_dp_tunnel_bw_alloc_is_enabled(struct intel_dp *intel_dp)
+{
+	return false;
+}
+
+static inline void
+intel_dp_tunnel_atomic_cleanup_inherited_state(struct intel_atomic_state *state) {}
+
+static inline int
+intel_dp_tunnel_atomic_compute_stream_bw(struct intel_atomic_state *state,
+					 struct intel_dp *intel_dp,
+					 const struct intel_connector *connector,
+					 struct intel_crtc_state *crtc_state)
+{
+	return 0;
+}
+
+static inline void
+intel_dp_tunnel_atomic_clear_stream_bw(struct intel_atomic_state *state,
+				       struct intel_crtc_state *crtc_state) {}
+
+static inline int
+intel_dp_tunnel_atomic_add_state_for_crtc(struct intel_atomic_state *state,
+					  struct intel_crtc *crtc)
+{
+	return 0;
+}
+
+static inline int
+intel_dp_tunnel_atomic_check_link(struct intel_atomic_state *state,
+				  struct intel_link_bw_limits *limits)
+{
+	return 0;
+}
+
+static inline int
+intel_dp_tunnel_atomic_check_state(struct intel_atomic_state *state,
+				   struct intel_dp *intel_dp,
+				   struct intel_connector *connector)
+{
+	return 0;
+}
+
+static inline int
+intel_dp_tunnel_atomic_alloc_bw(struct intel_atomic_state *state)
+{
+	return 0;
+}
+
+static inline int
+intel_dp_tunnel_mgr_init(struct drm_i915_private *i915)
+{
+	return 0;
+}
+
+static inline void intel_dp_tunnel_mgr_cleanup(struct drm_i915_private *i915) {}
+
+#endif /* CONFIG_DRM_I915_DP_TUNNEL */
+
+#endif /* __INTEL_DP_TUNNEL_H__ */