drm: Implement timings adjustments for frame packing

When using the frame packing and a single big framebuffer, some hardware
requires that we do everything like if we were scanning out the big
buffer itself. Let's instrument drm_mode_set_crtcinfo() to be able to do
this adjustement if the driver is asking for it.

v2: Use crtc_vtotal and multiply the clock by 2 instead of
    reconstructing it (Ville Syrjälä)

Suggested-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Acked-by: Dave Airlie <airlied@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/drm_modes.c

@@ -707,12 +707,18 @@ EXPORT_SYMBOL(drm_mode_vrefresh);
 /**
  * drm_mode_set_crtcinfo - set CRTC modesetting parameters
  * @p: mode
- * @adjust_flags: unused? (FIXME)
+ * @adjust_flags: a combination of adjustment flags
  *
  * LOCKING:
  * None.
  *
  * Setup the CRTC modesetting parameters for @p, adjusting if necessary.
+ *
+ * - The CRTC_INTERLACE_HALVE_V flag can be used to halve vertical timings of
+ *   interlaced modes.
+ * - The CRTC_STEREO_DOUBLE flag can be used to compute the timings for
+ *   buffers containing two eyes (only adjust the timings when needed, eg. for
+ *   "frame packing" or "side by side full").
  */
 void drm_mode_set_crtcinfo(struct drm_display_mode *p, int adjust_flags)
 {
@@ -753,6 +759,20 @@ void drm_mode_set_crtcinfo(struct drm_display_mode *p, int adjust_flags)
 		p->crtc_vtotal *= p->vscan;
 	}
 
+	if (adjust_flags & CRTC_STEREO_DOUBLE) {
+		unsigned int layout = p->flags & DRM_MODE_FLAG_3D_MASK;
+
+		switch (layout) {
+		case DRM_MODE_FLAG_3D_FRAME_PACKING:
+			p->crtc_clock *= 2;
+			p->crtc_vdisplay += p->crtc_vtotal;
+			p->crtc_vsync_start += p->crtc_vtotal;
+			p->crtc_vsync_end += p->crtc_vtotal;
+			p->crtc_vtotal += p->crtc_vtotal;
+			break;
+		}
+	}
+
 	p->crtc_vblank_start = min(p->crtc_vsync_start, p->crtc_vdisplay);
 	p->crtc_vblank_end = max(p->crtc_vsync_end, p->crtc_vtotal);
 	p->crtc_hblank_start = min(p->crtc_hsync_start, p->crtc_hdisplay);

include/drm/drm_crtc.h

@@ -125,7 +125,8 @@ enum drm_mode_status {
 	.vscan = (vs), .flags = (f), \
 	.base.type = DRM_MODE_OBJECT_MODE
 
-#define CRTC_INTERLACE_HALVE_V 0x1 /* halve V values for interlacing */
+#define CRTC_INTERLACE_HALVE_V	(1 << 0) /* halve V values for interlacing */
+#define CRTC_STEREO_DOUBLE	(1 << 1) /* adjust timings for stereo modes */
 
 struct drm_display_mode {
 	/* Header */