Tone, of course, is an author's attitude toward his subject. In this case the poem is written by John Donne. The tone is one of both exasperation about human love and peace felt within God's love.
The author, John Donne, definitely feels like human love is a two-edged sword. There is anguish involved, philosophically. The lover in the poem wants it "all," which means he wants sexual gratification from his lover. However, through the midst of the poem, the speaker also learns that once this is given to him, that there will be no more growth in the feeling of love. Wanting the fulfillment and yet knowing that growth of the feeling has an end is quite exasperating for the speaker. John Donne, as the author, already knows this. He is sharing it with the reader.
By the end of the poem, the speaker understands that there is an irony in the feeling of love. This brings the author's tone to an even greater level of anguish. You see, even by giving total and complete sexual gratification, one cannot sustain that feeling.
The ultimate revelation of this poem is that God's love is bigger and better than any other human love, even the most fantastic sexual form of love that humans can share.
In conclusion, it is important to note that John Donne does use a bit of humor in expressing the tone of anguish in human love and peace in God's love. You can see the humor in the puns found within the poem. However, that doesn't change the tone of the author's feeling of anguish in regards to the feeling of erotic love and peace in regards to the feeling of God's agape love.