drm/i915: Add support for interlaced display.

This doesn't change the clock limits (minimums), i.e. it won't make it
output 720x576 PAL nor 720x480 NTSC, but it will work with modes like
1080i etc. (including GLX and textured Xvideo, not sure about the
overlay).

Tested on i915 + analog VGA, it would be worth checking if newer chips
(and which ones) still support interlaced mode.

Signed-off-by: Krzysztof Halasa <khc@pm.waw.pl>
Signed-off-by: Eric Anholt <eric@anholt.net>

2 files changed, 15 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/intel_crt.c b/drivers/gpu/drm/i915/intel_crt.c
index e16ac5a28c3c..d5c130202396 100644
--- a/drivers/gpu/drm/i915/intel_crt.c
+++ b/drivers/gpu/drm/i915/intel_crt.c
@@ -569,7 +569,7 @@ void intel_crt_init(struct drm_device *dev)
                                    (1 << INTEL_ANALOG_CLONE_BIT) |
                                    (1 << INTEL_SDVO_LVDS_CLONE_BIT);
         intel_encoder->crtc_mask = (1 << 0) | (1 << 1);
-        connector->interlace_allowed = 0;
+        connector->interlace_allowed = 1;
         connector->doublescan_allowed = 0;
 
         drm_encoder_helper_add(&intel_encoder->enc, &intel_crt_helper_funcs);
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 36afe9409964..4c7c151114f7 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -2354,6 +2354,8 @@ static bool intel_crtc_mode_fixup(struct drm_crtc *crtc,
                 if (mode->clock * 3 > 27000 * 4)
                         return MODE_CLOCK_HIGH;
         }
+
+        drm_mode_set_crtcinfo(adjusted_mode, 0);
         return true;
 }
 
@@ -3781,6 +3783,18 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
                 }
         }
 
+        if (adjusted_mode->flags & DRM_MODE_FLAG_INTERLACE) {
+                pipeconf |= PIPECONF_INTERLACE_W_FIELD_INDICATION;
+                /* the chip adds 2 halflines automatically */
+                adjusted_mode->crtc_vdisplay -= 1;
+                adjusted_mode->crtc_vtotal -= 1;
+                adjusted_mode->crtc_vblank_start -= 1;
+                adjusted_mode->crtc_vblank_end -= 1;
+                adjusted_mode->crtc_vsync_end -= 1;
+                adjusted_mode->crtc_vsync_start -= 1;
+        } else
+                pipeconf &= ~PIPECONF_INTERLACE_W_FIELD_INDICATION; /* progressive */
+
         I915_WRITE(htot_reg, (adjusted_mode->crtc_hdisplay - 1) |
                    ((adjusted_mode->crtc_htotal - 1) << 16));
         I915_WRITE(hblank_reg, (adjusted_mode->crtc_hblank_start - 1) |