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

Author: ideak

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;