Implement struct drm_crtc_funcs.get_vblank_timestamp with the DRM
helper drm_crtc_vblank_helper_get_vblank_timestamp() with its helper
get_scanout_position. Read the scanout position from the MGAREG_VCOUNT
register.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240718104551.575912-8-tzimmermann@suse.de