The back porch timings were correct, only the sync offset was wrong.
Correct timing is now reported for 1080i and 576i, but the h offset is
incorrect for 480i for non-obvious reasons.
Fixes: fb10dc451c0f ("drm/vc4: hdmi: Correct HDMI timing registers for interlaced modes")
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Link: https://lore.kernel.org/r/20221207-rpi-hvs-crtc-misc-v1-14-1f8e0770798b@cerno.tech
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
                     VC4_SET_FIELD(mode->crtc_vdisplay, VC5_HDMI_VERTA_VAL));
        u32 vertb = (VC4_SET_FIELD(mode->htotal >> (2 - pixel_rep),
                                   VC5_HDMI_VERTB_VSPO) |
-                    VC4_SET_FIELD(mode->crtc_vtotal - mode->crtc_vsync_end,
+                    VC4_SET_FIELD(mode->crtc_vtotal - mode->crtc_vsync_end +
+                                  interlaced,
                                   VC4_HDMI_VERTB_VBP));
        u32 vertb_even = (VC4_SET_FIELD(0, VC5_HDMI_VERTB_VSPO) |
                          VC4_SET_FIELD(mode->crtc_vtotal -
-                                       mode->crtc_vsync_end - interlaced,
+                                       mode->crtc_vsync_end,
                                        VC4_HDMI_VERTB_VBP));
        unsigned long flags;
        unsigned char gcp;