drm/i915/display: Add drm_panic support for 4-tiling with DPT

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 <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Maarten Lankhorst <[email protected]>

Author: Jocelyn Falempe

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

@@ -1298,6 +1298,25 @@ static unsigned int intel_ytile_get_offset(unsigned int width, unsigned int x, u
 	return offset;
 }
 
+static unsigned int intel_4tile_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 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;
+	return offset;
+}
+
 static void intel_panic_flush(struct drm_plane *plane)
 {
 	struct intel_plane_state *plane_state = to_intel_plane_state(plane->state);
@@ -1341,6 +1360,7 @@ static unsigned int (*intel_get_tiling_func(u64 fb_modifier))(unsigned int width
 	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_get_offset;
 	case I915_FORMAT_MOD_X_TILED:
 	case I915_FORMAT_MOD_Yf_TILED:
 	case I915_FORMAT_MOD_Yf_TILED_CCS: