Wilford Woodruff reports Joseph teaching that the Father was a Saviour on a previous earth like Jesus is for our earth.
Discourse, January 30, 1842, The Joseph Smith Papers website, accessed April 9, 2022
Jan 30[th] [1842] Joseph the Seer taught the following principles that the God & father of our Lord Jesus Christ was once the same as the Son or Holy Ghost bothaving [both having] redeemed a world became the eternal God of that world he had a son Jesus Christ who redeemed this earth the same as his father had a world which made them equal & the Holy Ghost would do the same in his turn & so would all the Saint