drm: add helper to get crtc timings (v5)

We need to get hdisplay and vdisplay in a few places so create a
helper to make our job easier.

Note that drm_crtc_check_viewport() and intel_modeset_pipe_config() were
previously making adjustments for doublescan modes and vscan > 1 modes,
which was incorrect.  Using our new helper fixes this mistake.

v2 (by Matt): Use new stereo doubling function (suggested by Ville)

v3 (by Matt):
 - Add missing kerneldoc (Daniel)
 - Use drm_mode_copy() (Jani)

v4 (by Matt):
 - Drop stereo doubling function again; add 'stereo only' flag
   to drm_mode_set_crtcinfo() instead (Ville)

v5 (by Matt):
 - Note behavioral change in drm_crtc_check_viewport() and
   intel_modeset_pipe_config(). (Ander)
 - Describe new adjustment flags in drm_mode_set_crtcinfo()'s
   kerneldoc. (Ander)

Cc: dri-devel@lists.freedesktop.org
Suggested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Acked-by: Dave Airlie <airlied@gmail.com>
Reviewed-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 3a088c0..9eee2c9 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -10322,9 +10322,9 @@
 	 * computation to clearly distinguish it from the adjusted mode, which
 	 * can be changed by the connectors in the below retry loop.
 	 */
-	drm_mode_set_crtcinfo(&pipe_config->requested_mode, CRTC_STEREO_DOUBLE);
-	pipe_config->pipe_src_w = pipe_config->requested_mode.crtc_hdisplay;
-	pipe_config->pipe_src_h = pipe_config->requested_mode.crtc_vdisplay;
+	drm_crtc_get_hv_timing(&pipe_config->requested_mode,
+			       &pipe_config->pipe_src_w,
+			       &pipe_config->pipe_src_h);
 
 encoder_retry:
 	/* Ensure the port clock defaults are reset when retrying. */