From: Ville Syrjälä <[email protected]>

Let's switch the pipe into interlaced mode and switch off
the TV encoder vertical filter if the pipe vdisplay
matches the TV YSIZE exactly.

While I didn't measure it I presume this might reduce
the power consumption a little bit, and the pixel rate
is halved as the pipe will now fetching in interlaced
mode rather than in progressive mode (effectively the
same difference as between IF-ID vs. PF-ID pfit modes
on more modern hardware) so a bit easier on the memory
bandwidth.

Cc: Imre Deak <[email protected]>
Signed-off-by: Ville Syrjälä <[email protected]>
---
 drivers/gpu/drm/i915/intel_tv.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_tv.c b/drivers/gpu/drm/i915/intel_tv.c
index 3a5682f44e55..3924c4944e1f 100644
--- a/drivers/gpu/drm/i915/intel_tv.c
+++ b/drivers/gpu/drm/i915/intel_tv.c
@@ -1159,6 +1159,22 @@ intel_tv_get_config(struct intel_encoder *encoder,
                        I915_MODE_FLAG_USE_SCANLINE_COUNTER;
 }
 
+static bool intel_tv_source_too_wide(struct drm_i915_private *dev_priv,
+                                    int hdisplay)
+{
+       return IS_GEN(dev_priv, 3) && hdisplay > 1024;
+}
+
+static bool intel_tv_vert_scaling(const struct drm_display_mode *tv_mode,
+                                 const struct drm_connector_state *conn_state,
+                                 int vdisplay)
+{
+       return tv_mode->crtc_vdisplay -
+               conn_state->tv.margins.top -
+               conn_state->tv.margins.bottom !=
+               vdisplay;
+}
+
 static int
 intel_tv_compute_config(struct intel_encoder *encoder,
                        struct intel_crtc_state *pipe_config,
@@ -1189,7 +1205,8 @@ intel_tv_compute_config(struct intel_encoder *encoder,
        intel_tv_mode_to_mode(adjusted_mode, tv_mode);
        drm_mode_set_crtcinfo(adjusted_mode, 0);
 
-       if (IS_GEN(dev_priv, 3) && hdisplay > 1024) {
+       if (intel_tv_source_too_wide(dev_priv, hdisplay) ||
+           !intel_tv_vert_scaling(adjusted_mode, conn_state, vdisplay)) {
                int extra, top, bottom;
 
                extra = adjusted_mode->crtc_vdisplay - vdisplay;
-- 
2.19.2

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