drm/i915: Don't look at unrelated PIPECONF bits for interlaced readout

Since HSW the PIPECONF progressive vs. interlaced selection is done
with just two bits instead of the earlier three. Let's not look at the
extra bit on HSW+. Also gen2 doesn't support interlaced displays at all.

This is actually fine as is currently because the extra bit is mbz (as
are all three bits on gen2). But just to avoid mishaps in the future
if the bits get reused let's only look at what's properly defined.

v2: constify crtc_state
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190718145053.25808-8-ville.syrjala@linux.intel.comReviewed-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>

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

@@ -8203,6 +8203,21 @@ static void intel_set_pipe_src_size(const struct intel_crtc_state *crtc_state)
 		   (crtc_state->pipe_src_h - 1));
 }
 
+static bool intel_pipe_is_interlaced(const struct intel_crtc_state *crtc_state)
+{
+	struct drm_i915_private *dev_priv = to_i915(crtc_state->base.crtc->dev);
+	enum transcoder cpu_transcoder = crtc_state->cpu_transcoder;
+
+	if (IS_GEN(dev_priv, 2))
+		return false;
+
+	if (INTEL_GEN(dev_priv) >= 9 ||
+	    IS_BROADWELL(dev_priv) || IS_HASWELL(dev_priv))
+		return I915_READ(PIPECONF(cpu_transcoder)) & PIPECONF_INTERLACE_MASK_HSW;
+	else
+		return I915_READ(PIPECONF(cpu_transcoder)) & PIPECONF_INTERLACE_MASK;
+}
+
 static void intel_get_pipe_timings(struct intel_crtc *crtc,
 				   struct intel_crtc_state *pipe_config)
 {
@@ -8241,7 +8256,7 @@ static void intel_get_pipe_timings(struct intel_crtc *crtc,
 	pipe_config->base.adjusted_mode.crtc_vsync_start = (tmp & 0xffff) + 1;
 	pipe_config->base.adjusted_mode.crtc_vsync_end = ((tmp >> 16) & 0xffff) + 1;
 
-	if (I915_READ(PIPECONF(cpu_transcoder)) & PIPECONF_INTERLACE_MASK) {
+	if (intel_pipe_is_interlaced(pipe_config)) {
 		pipe_config->base.adjusted_mode.flags |= DRM_MODE_FLAG_INTERLACE;
 		pipe_config->base.adjusted_mode.crtc_vtotal += 1;
 		pipe_config->base.adjusted_mode.crtc_vblank_end += 1;