[PATCH v6 8/8] drm/i915/display: Add drm_panic support for 4-tiling with DPT

[Jocelyn Falempe <jfalempe@redhat.com>]

On Alder Lake and later, it's not possible to disable tiling when DPT
is enabled.
So this commit implements 4-Tiling support, to still be able to draw
the panic screen.

Signed-off-by: Jocelyn Falempe <jfalempe@redhat.com>
---
 .../gpu/drm/i915/display/intel_atomic_plane.c | 22 ++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_atomic_plane.c b/drivers/gpu/drm/i915/display/intel_atomic_plane.c
index 76c10555c10e..68deffe3aa9a 100644
--- a/drivers/gpu/drm/i915/display/intel_atomic_plane.c
+++ b/drivers/gpu/drm/i915/display/intel_atomic_plane.c
@@ -1289,6 +1289,25 @@ static void intel_ytile_set_pixel(struct drm_scanout_buffer *sb, unsigned int x,
 	iosys_map_wr(&sb->map[0], offset, u32, color);
 }
 
+static void intel_4tile_set_pixel(struct drm_scanout_buffer *sb, unsigned int x, unsigned int y,
+				  u32 color)
+{
+	u32 offset;
+	unsigned int swizzle;
+	unsigned int width_in_blocks = DIV_ROUND_UP(sb->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 y4 y3 x4 y2 x3 x2 y1 y0 x1 x0 */
+	swizzle = (x & 3) | ((y & 3) << 2) | ((x & 0xc) << 2) | (y & 4) << 4 | ((x & 0x10) << 3) | ((y & 0x18) << 5);
+	offset += swizzle * 4;
+	iosys_map_wr(&sb->map[0], offset, u32, color);
+}
+
 static void intel_panic_flush(struct drm_plane *plane)
 {
 	struct intel_plane_state *plane_state = to_intel_plane_state(plane->state);
@@ -1323,7 +1342,6 @@ static void (*intel_get_tiling_func(u64 fb_modifier))(struct drm_scanout_buffer
 	case I915_FORMAT_MOD_Y_TILED_GEN12_RC_CCS:
 	case I915_FORMAT_MOD_Y_TILED_GEN12_MC_CCS:
 		return intel_ytile_set_pixel;
-	case I915_FORMAT_MOD_X_TILED:
 	case I915_FORMAT_MOD_4_TILED:
 	case I915_FORMAT_MOD_4_TILED_DG2_RC_CCS:
 	case I915_FORMAT_MOD_4_TILED_DG2_MC_CCS:
@@ -1333,6 +1351,8 @@ static void (*intel_get_tiling_func(u64 fb_modifier))(struct drm_scanout_buffer
 	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:
+		return intel_4tile_set_pixel;
+	case I915_FORMAT_MOD_X_TILED:
 	case I915_FORMAT_MOD_Yf_TILED:
 	case I915_FORMAT_MOD_Yf_TILED_CCS:
 	default:
-- 
2.49.0