drm/i915/dsi: Assert that vfp+vsync+vbp == vtotal on BXT/GLK

Windows code seems to do some dodgy looking +/-1 adjustments
to some of the vertical timings. Not sure if that's correct
or not, but let's at least cross check some of the values
we got from the hardware to double check whether the GOP
did the same or not.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250314150136.22564-3-ville.syrjala@linux.intel.com
Acked-by: Jani Nikula <jani.nikula@intel.com>

Author: vsyrjala

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

@@ -1019,7 +1019,7 @@ static void bxt_dsi_get_pipe_config(struct intel_encoder *encoder,
 	unsigned int lane_count = intel_dsi->lane_count;
 	unsigned int bpp, fmt;
 	enum port port;
-	u16 hactive, hfp, hsync, hbp, vfp, vsync;
+	u16 hactive, hfp, hsync, hbp, vfp, vsync, vbp;
 	u16 hfp_sw, hsync_sw, hbp_sw;
 	u16 crtc_htotal_sw, crtc_hsync_start_sw, crtc_hsync_end_sw,
 				crtc_hblank_start_sw, crtc_hblank_end_sw;
@@ -1083,6 +1083,7 @@ static void bxt_dsi_get_pipe_config(struct intel_encoder *encoder,
 
 	/* vertical values are in terms of lines */
 	vfp = intel_de_read(display, MIPI_VFP_COUNT(display, port));
+	vbp = intel_de_read(display, MIPI_VBP_COUNT(display, port));
 	vsync = intel_de_read(display, MIPI_VSYNC_PADDING_COUNT(display, port));
 
 	adjusted_mode->crtc_htotal = hactive + hfp + hsync + hbp;
@@ -1091,6 +1092,8 @@ static void bxt_dsi_get_pipe_config(struct intel_encoder *encoder,
 	adjusted_mode->crtc_hblank_start = adjusted_mode->crtc_hdisplay;
 	adjusted_mode->crtc_hblank_end = adjusted_mode->crtc_htotal;
 
+	drm_WARN_ON(display->drm, adjusted_mode->crtc_vdisplay +
+		    vfp + vsync + vbp != adjusted_mode->crtc_vtotal);
 	adjusted_mode->crtc_vsync_start = vfp + adjusted_mode->crtc_vdisplay;
 	adjusted_mode->crtc_vsync_end = vsync + adjusted_mode->crtc_vsync_start;
 	adjusted_mode->crtc_vblank_start = adjusted_mode->crtc_vdisplay;