drm/i915/display: Add drm_panic support for Y-tiling with DPT

On Alder Lake and later, it's not possible to disable tiling when DPT
is enabled.
So this commit implements Y-Tiling support, to still be able to draw
the panic screen.

Signed-off-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://lore.kernel.org/r/20250624091501.257661-10-jfalempe@redhat.com
Signed-off-by: Maarten Lankhorst <dev@lankhorst.se>

Author: Jocelyn Falempe

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

@@ -146,6 +146,8 @@ struct intel_framebuffer {
 
 	unsigned int min_alignment;
 	unsigned int vtd_guard;
+
+	unsigned int (*panic_tiling)(unsigned int x, unsigned int y, unsigned int width);
 };
 
 enum intel_hotplug_state {

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

@@ -1272,6 +1272,32 @@ intel_cleanup_plane_fb(struct drm_plane *plane,
 	intel_plane_unpin_fb(old_plane_state);
 }
 
+/* Handle Y-tiling, only if DPT is enabled (otherwise disabling tiling is easier)
+ * All DPT hardware have 128-bytes width tiling, so Y-tile dimension is 32x32
+ * pixels for 32bits pixels.
+ */
+#define YTILE_WIDTH	32
+#define YTILE_HEIGHT	32
+#define YTILE_SIZE (YTILE_WIDTH * YTILE_HEIGHT * 4)
+
+static unsigned int intel_ytile_get_offset(unsigned int width, unsigned int x, unsigned int y)
+{
+	u32 offset;
+	unsigned int swizzle;
+	unsigned int width_in_blocks = DIV_ROUND_UP(width, 32);
+
+	/* Block offset */
+	offset = ((y / YTILE_HEIGHT) * width_in_blocks + (x / YTILE_WIDTH)) * YTILE_SIZE;
+
+	x = x % YTILE_WIDTH;
+	y = y % YTILE_HEIGHT;
+
+	/* bit order inside a block is x4 x3 x2 y4 y3 y2 y1 y0 x1 x0 */
+	swizzle = (x & 3) | ((y & 0x1f) << 2) | ((x & 0x1c) << 5);
+	offset += swizzle * 4;
+	return offset;
+}
+
 static void intel_panic_flush(struct drm_plane *plane)
 {
 	struct intel_plane_state *plane_state = to_intel_plane_state(plane->state);
@@ -1295,6 +1321,35 @@ static void intel_panic_flush(struct drm_plane *plane)
 		iplane->disable_tiling(iplane);
 }
 
+static unsigned int (*intel_get_tiling_func(u64 fb_modifier))(unsigned int width,
+							      unsigned int x,
+							      unsigned int y)
+{
+	switch (fb_modifier) {
+	case I915_FORMAT_MOD_Y_TILED:
+	case I915_FORMAT_MOD_Y_TILED_CCS:
+	case I915_FORMAT_MOD_Y_TILED_GEN12_RC_CCS_CC:
+	case I915_FORMAT_MOD_Y_TILED_GEN12_RC_CCS:
+	case I915_FORMAT_MOD_Y_TILED_GEN12_MC_CCS:
+		return intel_ytile_get_offset;
+	case I915_FORMAT_MOD_4_TILED:
+	case I915_FORMAT_MOD_4_TILED_DG2_RC_CCS:
+	case I915_FORMAT_MOD_4_TILED_DG2_MC_CCS:
+	case I915_FORMAT_MOD_4_TILED_DG2_RC_CCS_CC:
+	case I915_FORMAT_MOD_4_TILED_MTL_RC_CCS:
+	case I915_FORMAT_MOD_4_TILED_MTL_RC_CCS_CC:
+	case I915_FORMAT_MOD_4_TILED_MTL_MC_CCS:
+	case I915_FORMAT_MOD_4_TILED_BMG_CCS:
+	case I915_FORMAT_MOD_4_TILED_LNL_CCS:
+	case I915_FORMAT_MOD_X_TILED:
+	case I915_FORMAT_MOD_Yf_TILED:
+	case I915_FORMAT_MOD_Yf_TILED_CCS:
+	default:
+	/* Not supported yet */
+		return NULL;
+	}
+}
+
 static int intel_get_scanout_buffer(struct drm_plane *plane,
 				    struct drm_scanout_buffer *sb)
 {
@@ -1320,8 +1375,13 @@ static int intel_get_scanout_buffer(struct drm_plane *plane,
 	} else {
 		int ret;
 		/* Can't disable tiling if DPT is in use */
-		if (intel_fb_uses_dpt(fb))
-			return -EOPNOTSUPP;
+		if (intel_fb_uses_dpt(fb)) {
+			if (fb->format->cpp[0] != 4)
+				return -EOPNOTSUPP;
+			intel_fb->panic_tiling = intel_get_tiling_func(fb->modifier);
+			if (!intel_fb->panic_tiling)
+				return -EOPNOTSUPP;
+		}
 		sb->private = intel_fb;
 		ret = intel_bo_panic_setup(sb);
 		if (ret)

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

@@ -2795,15 +2795,22 @@ static void skl_disable_tiling(struct intel_plane *plane)
 {
 	struct intel_plane_state *state = to_intel_plane_state(plane->base.state);
 	struct intel_display *display = to_intel_display(plane);
-	u32 stride = state->view.color_plane[0].scanout_stride / 64;
+	const struct drm_framebuffer *fb = state->hw.fb;
 	u32 plane_ctl;
 
 	plane_ctl = intel_de_read(display, PLANE_CTL(plane->pipe, plane->id));
-	plane_ctl &= ~PLANE_CTL_TILED_MASK;
 
-	intel_de_write_fw(display, PLANE_STRIDE(plane->pipe, plane->id),
-			  PLANE_STRIDE_(stride));
+	if (intel_fb_uses_dpt(fb)) {
+		/* if DPT is enabled, keep tiling, but disable compression */
+		plane_ctl &= ~PLANE_CTL_RENDER_DECOMPRESSION_ENABLE;
+	} else {
+		/* if DPT is not supported, disable tiling, and update stride */
+		u32 stride = state->view.color_plane[0].scanout_stride / 64;
 
+		plane_ctl &= ~PLANE_CTL_TILED_MASK;
+		intel_de_write_fw(display, PLANE_STRIDE(plane->pipe, plane->id),
+				  PLANE_STRIDE_(stride));
+	}
 	intel_de_write_fw(display, PLANE_CTL(plane->pipe, plane->id), plane_ctl);
 
 	intel_de_write_fw(display, PLANE_SURF(plane->pipe, plane->id),

drivers/gpu/drm/i915/gem/i915_gem_pages.c

@@ -400,6 +400,15 @@ static struct page **i915_gem_object_panic_pages(struct drm_i915_gem_object *obj
 	return pages;
 }
 
+static void i915_gem_object_panic_map_set_pixel(struct drm_scanout_buffer *sb, unsigned int x,
+						unsigned int y, u32 color)
+{
+	struct intel_framebuffer *fb = (struct intel_framebuffer *)sb->private;
+	unsigned int offset = fb->panic_tiling(sb->width, x, y);
+
+	iosys_map_wr(&sb->map[0], offset, u32, color);
+}
+
 /*
  * The scanout buffer pages are not mapped, so for each pixel,
  * use kmap_local_page_try_from_panic() to map the page, and write the pixel.
@@ -413,7 +422,10 @@ static void i915_gem_object_panic_page_set_pixel(struct drm_scanout_buffer *sb,
 	struct intel_framebuffer *fb = (struct intel_framebuffer *)sb->private;
 	struct i915_panic_data *panic = to_i915_panic_data(fb);
 
-	offset = y * sb->pitch[0] + x * sb->format->cpp[0];
+	if (fb->panic_tiling)
+		offset = fb->panic_tiling(sb->width, x, y);
+	else
+		offset = y * sb->pitch[0] + x * sb->format->cpp[0];
 
 	new_page = offset >> PAGE_SHIFT;
 	offset = offset % PAGE_SIZE;
@@ -459,6 +471,8 @@ int i915_gem_object_panic_setup(struct drm_scanout_buffer *sb)
 		else
 			iosys_map_set_vaddr(&sb->map[0], ptr);
 
+		if (fb->panic_tiling)
+			sb->set_pixel = i915_gem_object_panic_map_set_pixel;
 		return 0;
 	}
 	if (i915_gem_object_has_struct_page(obj)) {

drivers/gpu/drm/xe/display/intel_bo.c

@@ -104,7 +104,10 @@ static void xe_panic_page_set_pixel(struct drm_scanout_buffer *sb, unsigned int
 	unsigned int new_page;
 	unsigned int offset;
 
-	offset = y * sb->pitch[0] + x * sb->format->cpp[0];
+	if (fb->panic_tiling)
+		offset = fb->panic_tiling(sb->width, x, y);
+	else
+		offset = y * sb->pitch[0] + x * sb->format->cpp[0];
 
 	new_page = offset >> PAGE_SHIFT;
 	offset = offset % PAGE_SIZE;