drm/i915: Skip aux plane stuff when there is no aux plane

when the hardware isn't going to use the aux plane there's no
real point in dealing with the relevant hardware restrictions.
So let's just skip all that when not necessary.

We can now also remove the offset=~0xfff behaviour for unused
color planes. Let's just zero out everyting so as to not leave
stale garbage behind to confuse people debugging the code.

v2: Explicitly set AUX_DIST to zero when there is no aux plane

Reviewed-by: Imre Deak <imre.deak@intel.com> #v1
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201009120028.32422-1-ville.syrjala@linux.intel.com

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

@@ -2001,13 +2001,17 @@ static int ccs_to_main_plane(const struct drm_framebuffer *fb, int ccs_plane)
 	return ccs_plane - fb->format->num_planes / 2;
 }
 
-/* Return either the main plane's CCS or - if not a CCS FB - UV plane */
 int intel_main_to_aux_plane(const struct drm_framebuffer *fb, int main_plane)
 {
+	struct drm_i915_private *i915 = to_i915(fb->dev);
+
 	if (is_ccs_modifier(fb->modifier))
 		return main_to_ccs_plane(fb, main_plane);
-
-	return 1;
+	else if (INTEL_GEN(i915) < 11 &&
+		 intel_format_info_is_yuv_semiplanar(fb->format, fb->modifier))
+		return 1;
+	else
+		return 0;
 }
 
 bool
@@ -3933,7 +3937,7 @@ static int skl_check_main_surface(struct intel_plane_state *plane_state)
 	 * main surface offset, and it must be non-negative. Make
 	 * sure that is what we will get.
 	 */
-	if (offset > aux_offset)
+	if (aux_plane && offset > aux_offset)
 		offset = intel_plane_adjust_aligned_offset(&x, &y, plane_state, 0,
 							   offset, aux_offset & ~(alignment - 1));
 
@@ -4131,7 +4135,7 @@ int skl_check_plane_surface(struct intel_plane_state *plane_state)
 	}
 
 	for (i = fb->format->num_planes; i < ARRAY_SIZE(plane_state->color_plane); i++) {
-		plane_state->color_plane[i].offset = ~0xfff;
+		plane_state->color_plane[i].offset = 0;
 		plane_state->color_plane[i].x = 0;
 		plane_state->color_plane[i].y = 0;
 	}

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

@@ -655,8 +655,6 @@ skl_program_plane(struct intel_plane *plane,
 	u32 stride = skl_plane_stride(plane_state, color_plane);
 	const struct drm_framebuffer *fb = plane_state->hw.fb;
 	int aux_plane = intel_main_to_aux_plane(fb, color_plane);
-	u32 aux_dist = plane_state->color_plane[aux_plane].offset - surf_addr;
-	u32 aux_stride = skl_plane_stride(plane_state, aux_plane);
 	int crtc_x = plane_state->uapi.dst.x1;
 	int crtc_y = plane_state->uapi.dst.y1;
 	u32 x = plane_state->color_plane[color_plane].x;
@@ -664,7 +662,7 @@ skl_program_plane(struct intel_plane *plane,
 	u32 src_w = drm_rect_width(&plane_state->uapi.src) >> 16;
 	u32 src_h = drm_rect_height(&plane_state->uapi.src) >> 16;
 	u8 alpha = plane_state->hw.alpha >> 8;
-	u32 plane_color_ctl = 0;
+	u32 plane_color_ctl = 0, aux_dist = 0;
 	unsigned long irqflags;
 	u32 keymsk, keymax;
 	u32 plane_ctl = plane_state->ctl;
@@ -691,6 +689,13 @@ skl_program_plane(struct intel_plane *plane,
 		crtc_y = 0;
 	}
 
+	if (aux_plane) {
+		aux_dist = plane_state->color_plane[aux_plane].offset - surf_addr;
+
+		if (INTEL_GEN(dev_priv) < 12)
+			aux_dist |= skl_plane_stride(plane_state, aux_plane);
+	}
+
 	spin_lock_irqsave(&dev_priv->uncore.lock, irqflags);
 
 	intel_de_write_fw(dev_priv, PLANE_STRIDE(pipe, plane_id), stride);
@@ -699,8 +704,6 @@ skl_program_plane(struct intel_plane *plane,
 	intel_de_write_fw(dev_priv, PLANE_SIZE(pipe, plane_id),
 			  (src_h << 16) | src_w);
 
-	if (INTEL_GEN(dev_priv) < 12)
-		aux_dist |= aux_stride;
 	intel_de_write_fw(dev_priv, PLANE_AUX_DIST(pipe, plane_id), aux_dist);
 
 	if (icl_is_hdr_plane(dev_priv, plane_id))