[PATCH] drm/{i915, xe}/display: pass parent interface to display probe

[Jani Nikula <jani.nikula@intel.com>]

Let's gradually start calling i915 and xe parent, or core, drivers from
display via function pointers passed at display probe.

For starters, just add a small feature test hook ->has_flat_ccs. While
it's platform specific for platforms supported by i915, the newer
platforms in xe may have it fused off, and need a dynamic check.

Going forward, the struct intel_display_parent_interface is expected to
include const pointers to sub-structs by functionality, for example:

struct intel_display_rpm {
	struct ref_tracker *(*get)(struct drm_device *drm);
	/* ... */
};

struct intel_display_parent_interface {
	/* ... */
	const struct intel_display_rpm *rpm;
};

This is a baby step towards not building display as part of both i915
and xe drivers, but rather making it an independent driver interfacing
with the two.

Cc: Jouni Högander <jouni.hogander@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

---

v1 after RFC [1], with some naming improvements etc.

[1] https://lore.kernel.org/r/20251003092107.2892508-1-jani.nikula@intel.com
---
 .../gpu/drm/i915/display/intel_display_core.h |  4 +++
 .../drm/i915/display/intel_display_device.c   |  5 +++-
 .../drm/i915/display/intel_display_device.h   |  4 ++-
 drivers/gpu/drm/i915/display/intel_fb.c       |  5 ++--
 .../drm/i915/display/skl_universal_plane.c    |  5 ++--
 drivers/gpu/drm/i915/i915_driver.c            | 17 ++++++++++-
 drivers/gpu/drm/i915/i915_driver.h            |  2 ++
 .../gpu/drm/i915/selftests/mock_gem_device.c  |  4 ++-
 .../gpu/drm/xe/compat-i915-headers/i915_drv.h |  2 --
 drivers/gpu/drm/xe/display/xe_display.c       | 12 +++++++-
 include/drm/intel/display_parent_interface.h  | 28 +++++++++++++++++++
 11 files changed, 76 insertions(+), 12 deletions(-)
 create mode 100644 include/drm/intel/display_parent_interface.h

diff --git a/drivers/gpu/drm/i915/display/intel_display_core.h b/drivers/gpu/drm/i915/display/intel_display_core.h
index df4da52cbdb3..ebbfcd5efe84 100644
--- a/drivers/gpu/drm/i915/display/intel_display_core.h
+++ b/drivers/gpu/drm/i915/display/intel_display_core.h
@@ -41,6 +41,7 @@ struct intel_cdclk_vals;
 struct intel_color_funcs;
 struct intel_crtc;
 struct intel_crtc_state;
+struct intel_display_parent_interface;
 struct intel_dmc;
 struct intel_dpll_global_funcs;
 struct intel_dpll_mgr;
@@ -291,6 +292,9 @@ struct intel_display {
 	/* Intel PCH: where the south display engine lives */
 	enum intel_pch pch_type;
 
+	/* Parent, or core, driver functions exposed to display */
+	const struct intel_display_parent_interface *parent;
+
 	/* Display functions */
 	struct {
 		/* Top level crtc-ish functions */
diff --git a/drivers/gpu/drm/i915/display/intel_display_device.c b/drivers/gpu/drm/i915/display/intel_display_device.c
index f3f1f25b0f38..328447a5e5e8 100644
--- a/drivers/gpu/drm/i915/display/intel_display_device.c
+++ b/drivers/gpu/drm/i915/display/intel_display_device.c
@@ -1647,7 +1647,8 @@ static void display_platforms_or(struct intel_display_platforms *dst,
 	bitmap_or(dst->bitmap, dst->bitmap, src->bitmap, display_platforms_num_bits());
 }
 
-struct intel_display *intel_display_device_probe(struct pci_dev *pdev)
+struct intel_display *intel_display_device_probe(struct pci_dev *pdev,
+						 const struct intel_display_parent_interface *parent)
 {
 	struct intel_display *display;
 	const struct intel_display_device_info *info;
@@ -1663,6 +1664,8 @@ struct intel_display *intel_display_device_probe(struct pci_dev *pdev)
 	/* Add drm device backpointer as early as possible. */
 	display->drm = pci_get_drvdata(pdev);
 
+	display->parent = parent;
+
 	intel_display_params_copy(&display->params);
 
 	if (has_no_display(pdev)) {
diff --git a/drivers/gpu/drm/i915/display/intel_display_device.h b/drivers/gpu/drm/i915/display/intel_display_device.h
index 0e062753cf9b..c570c177a8e1 100644
--- a/drivers/gpu/drm/i915/display/intel_display_device.h
+++ b/drivers/gpu/drm/i915/display/intel_display_device.h
@@ -13,6 +13,7 @@
 
 struct drm_printer;
 struct intel_display;
+struct intel_display_parent_interface;
 struct pci_dev;
 
 /*
@@ -310,7 +311,8 @@ struct intel_display_device_info {
 
 bool intel_display_device_present(struct intel_display *display);
 bool intel_display_device_enabled(struct intel_display *display);
-struct intel_display *intel_display_device_probe(struct pci_dev *pdev);
+struct intel_display *intel_display_device_probe(struct pci_dev *pdev,
+						 const struct intel_display_parent_interface *parent);
 void intel_display_device_remove(struct intel_display *display);
 void intel_display_device_info_runtime_init(struct intel_display *display);
 
diff --git a/drivers/gpu/drm/i915/display/intel_fb.c b/drivers/gpu/drm/i915/display/intel_fb.c
index 69237dabdae8..957416b69fa1 100644
--- a/drivers/gpu/drm/i915/display/intel_fb.c
+++ b/drivers/gpu/drm/i915/display/intel_fb.c
@@ -9,6 +9,7 @@
 #include <drm/drm_blend.h>
 #include <drm/drm_gem.h>
 #include <drm/drm_modeset_helper.h>
+#include <drm/intel/display_parent_interface.h>
 
 #include "i915_drv.h"
 #include "i915_utils.h"
@@ -547,8 +548,6 @@ static bool plane_has_modifier(struct intel_display *display,
 			       u8 plane_caps,
 			       const struct intel_modifier_desc *md)
 {
-	struct drm_i915_private *i915 = to_i915(display->drm);
-
 	if (!IS_DISPLAY_VER(display, md->display_ver.from, md->display_ver.until))
 		return false;
 
@@ -560,7 +559,7 @@ static bool plane_has_modifier(struct intel_display *display,
 	 * where supported.
 	 */
 	if (intel_fb_is_ccs_modifier(md->modifier) &&
-	    HAS_FLAT_CCS(i915) != !md->ccs.packed_aux_planes)
+	    display->parent->has_flat_ccs(display->drm) != !md->ccs.packed_aux_planes)
 		return false;
 
 	if (md->modifier == I915_FORMAT_MOD_4_TILED_BMG_CCS &&
diff --git a/drivers/gpu/drm/i915/display/skl_universal_plane.c b/drivers/gpu/drm/i915/display/skl_universal_plane.c
index e13fb781e7b2..1c78165839ed 100644
--- a/drivers/gpu/drm/i915/display/skl_universal_plane.c
+++ b/drivers/gpu/drm/i915/display/skl_universal_plane.c
@@ -7,6 +7,7 @@
 #include <drm/drm_blend.h>
 #include <drm/drm_damage_helper.h>
 #include <drm/drm_fourcc.h>
+#include <drm/intel/display_parent_interface.h>
 
 #include "pxp/intel_pxp.h"
 #include "i915_drv.h"
@@ -1572,7 +1573,7 @@ icl_plane_update_noarm(struct intel_dsb *dsb,
 	}
 
 	/* FLAT CCS doesn't need to program AUX_DIST */
-	if (!HAS_FLAT_CCS(to_i915(display->drm)) && DISPLAY_VER(display) < 20)
+	if (!display->parent->has_flat_ccs(display->drm) && DISPLAY_VER(display) < 20)
 		intel_de_write_dsb(display, dsb, PLANE_AUX_DIST(pipe, plane_id),
 				   skl_plane_aux_dist(plane_state, color_plane));
 
@@ -2930,7 +2931,7 @@ skl_universal_plane_create(struct intel_display *display,
 		caps = skl_plane_caps(display, pipe, plane_id);
 
 	/* FIXME: xe has problems with AUX */
-	if (!IS_ENABLED(I915) && !HAS_FLAT_CCS(to_i915(display->drm)))
+	if (!IS_ENABLED(I915) && !display->parent->has_flat_ccs(display->drm))
 		caps &= ~(INTEL_PLANE_CAP_CCS_RC |
 			  INTEL_PLANE_CAP_CCS_RC_CC |
 			  INTEL_PLANE_CAP_CCS_MC);
diff --git a/drivers/gpu/drm/i915/i915_driver.c b/drivers/gpu/drm/i915/i915_driver.c
index b46cb54ef5dc..a314799e4748 100644
--- a/drivers/gpu/drm/i915/i915_driver.c
+++ b/drivers/gpu/drm/i915/i915_driver.c
@@ -47,6 +47,7 @@
 #include <drm/drm_managed.h>
 #include <drm/drm_probe_helper.h>
 #include <drm/intel/display_member.h>
+#include <drm/intel/display_parent_interface.h>
 
 #include "display/i9xx_display_sr.h"
 #include "display/intel_bw.h"
@@ -738,6 +739,20 @@ static void i915_welcome_messages(struct drm_i915_private *dev_priv)
 			 "DRM_I915_DEBUG_RUNTIME_PM enabled\n");
 }
 
+static bool has_flat_ccs(struct drm_device *drm)
+{
+	return HAS_FLAT_CCS(to_i915(drm));
+}
+
+static const struct intel_display_parent_interface parent = {
+	.has_flat_ccs = has_flat_ccs,
+};
+
+const struct intel_display_parent_interface *i915_driver_parent_interface(void)
+{
+	return &parent;
+}
+
 /* Ensure drm and display members are placed properly. */
 INTEL_DISPLAY_MEMBER_STATIC_ASSERT(struct drm_i915_private, drm, display);
 
@@ -762,7 +777,7 @@ i915_driver_create(struct pci_dev *pdev, const struct pci_device_id *ent)
 	/* Set up device info and initial runtime info. */
 	intel_device_info_driver_create(i915, pdev->device, match_info);
 
-	display = intel_display_device_probe(pdev);
+	display = intel_display_device_probe(pdev, &parent);
 	if (IS_ERR(display))
 		return ERR_CAST(display);
 
diff --git a/drivers/gpu/drm/i915/i915_driver.h b/drivers/gpu/drm/i915/i915_driver.h
index 1e95ecb2a163..9551519ab429 100644
--- a/drivers/gpu/drm/i915/i915_driver.h
+++ b/drivers/gpu/drm/i915/i915_driver.h
@@ -12,6 +12,7 @@ struct pci_dev;
 struct pci_device_id;
 struct drm_i915_private;
 struct drm_printer;
+struct intel_display_parent_interface;
 
 #define DRIVER_NAME		"i915"
 #define DRIVER_DESC		"Intel Graphics"
@@ -24,6 +25,7 @@ void i915_driver_shutdown(struct drm_i915_private *i915);
 
 int i915_driver_resume_switcheroo(struct drm_i915_private *i915);
 int i915_driver_suspend_switcheroo(struct drm_i915_private *i915, pm_message_t state);
+const struct intel_display_parent_interface *i915_driver_parent_interface(void);
 
 void
 i915_print_iommu_status(struct drm_i915_private *i915, struct drm_printer *p);
diff --git a/drivers/gpu/drm/i915/selftests/mock_gem_device.c b/drivers/gpu/drm/i915/selftests/mock_gem_device.c
index fb8751bd5df0..b59626c4994c 100644
--- a/drivers/gpu/drm/i915/selftests/mock_gem_device.c
+++ b/drivers/gpu/drm/i915/selftests/mock_gem_device.c
@@ -33,6 +33,7 @@
 #include "gt/intel_gt.h"
 #include "gt/intel_gt_requests.h"
 #include "gt/mock_engine.h"
+#include "i915_driver.h"
 #include "intel_memory_region.h"
 #include "intel_region_ttm.h"
 
@@ -183,7 +184,8 @@ struct drm_i915_private *mock_gem_device(void)
 	/* Set up device info and initial runtime info. */
 	intel_device_info_driver_create(i915, pdev->device, &mock_info);
 
-	display = intel_display_device_probe(pdev);
+	/* FIXME: Can we run selftests using a mock device without display? */
+	display = intel_display_device_probe(pdev, i915_driver_parent_interface());
 	if (IS_ERR(display))
 		goto err_device;
 
diff --git a/drivers/gpu/drm/xe/compat-i915-headers/i915_drv.h b/drivers/gpu/drm/xe/compat-i915-headers/i915_drv.h
index b8269391bc69..a0311926b50b 100644
--- a/drivers/gpu/drm/xe/compat-i915-headers/i915_drv.h
+++ b/drivers/gpu/drm/xe/compat-i915-headers/i915_drv.h
@@ -12,7 +12,6 @@
 
 #include <drm/drm_drv.h>
 
-#include "xe_device.h" /* for xe_device_has_flat_ccs() */
 #include "xe_device_types.h"
 
 static inline struct drm_i915_private *to_i915(const struct drm_device *dev)
@@ -35,7 +34,6 @@ static inline struct drm_i915_private *to_i915(const struct drm_device *dev)
 
 #define IS_MOBILE(xe) (xe && 0)
 
-#define HAS_FLAT_CCS(xe) (xe_device_has_flat_ccs(xe))
 #define HAS_128_BYTE_Y_TILING(xe) (xe || 1)
 
 #endif
diff --git a/drivers/gpu/drm/xe/display/xe_display.c b/drivers/gpu/drm/xe/display/xe_display.c
index 5f4044e63185..f44ef8836a8f 100644
--- a/drivers/gpu/drm/xe/display/xe_display.c
+++ b/drivers/gpu/drm/xe/display/xe_display.c
@@ -14,6 +14,7 @@
 #include <drm/drm_managed.h>
 #include <drm/drm_probe_helper.h>
 #include <drm/intel/display_member.h>
+#include <drm/intel/display_parent_interface.h>
 #include <uapi/drm/xe_drm.h>
 
 #include "soc/intel_dram.h"
@@ -515,6 +516,15 @@ static void display_device_remove(struct drm_device *dev, void *arg)
 	intel_display_device_remove(display);
 }
 
+static bool has_flat_ccs(struct drm_device *drm)
+{
+	return xe_device_has_flat_ccs(to_xe_device(drm));
+}
+
+static const struct intel_display_parent_interface parent = {
+	.has_flat_ccs = has_flat_ccs,
+};
+
 /**
  * xe_display_probe - probe display and create display struct
  * @xe: XE device instance
@@ -535,7 +545,7 @@ int xe_display_probe(struct xe_device *xe)
 	if (!xe->info.probe_display)
 		goto no_display;
 
-	display = intel_display_device_probe(pdev);
+	display = intel_display_device_probe(pdev, &parent);
 	if (IS_ERR(display))
 		return PTR_ERR(display);
 
diff --git a/include/drm/intel/display_parent_interface.h b/include/drm/intel/display_parent_interface.h
new file mode 100644
index 000000000000..ef03b7e45405
--- /dev/null
+++ b/include/drm/intel/display_parent_interface.h
@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: MIT */
+/* Copyright © 2025 Intel Corporation x*/
+
+#ifndef __DISPLAY_PARENT_INTERFACE_H__
+#define __DISPLAY_PARENT_INTERFACE_H__
+
+#include <linux/types.h>
+
+struct drm_device;
+
+/**
+ * struct intel_display_parent_interface - services parent driver provides to display
+ *
+ * The parent, or core, driver provides a pointer to this structure to display
+ * driver when calling intel_display_device_probe(). The display driver uses it
+ * to access services provided by the parent driver. The structure may contain
+ * sub-struct pointers to group function pointers by functionality.
+ *
+ * All function and sub-struct pointers must be initialized and callable unless
+ * explicitly marked as "optional" below. The display driver will only NULL
+ * check the optional pointers.
+ */
+struct intel_display_parent_interface {
+	/** @has_flat_ccs: does the device support flat CCS */
+	bool (*has_flat_ccs)(struct drm_device *drm);
+};
+
+#endif
-- 
2.47.3