I am having a concern about a rule. When looking at Falling damage (p. 303 DMG) it says

Falling Damage: The basic rule is simple: 1d6 points of damage per 10 feet fallen, to a maximum of 20d6.

then there is this sentence:

If a character deliberately jumps instead of merely slipping or falling, the damage is the same but the first 1d6 is nonlethal dam- age.

So, after this you go into the PHB for clarifications on jump and jump (p. 77, PHB) has 4 ways to use its skill: long jump, high jump, hop up and jump down. In the jump down section states the same as in DMG.

If you intentionally jump from a height, you take less damage than you would if you just fell. The DC to jump down from a height is 15 [...] If you succeed on the check, you take falling damage as if you had dropped 10 fewer feet than you actually did. Thus, if you jump down from a height of just 10 feet, you take no damage. If you jump down from a height of 20 feet, you take damage as if you had fallen 10 feet.

Then there is the long jump rule

Long Jump: A long jump is a horizontal jump, made across a gap like a chasm or stream. At the midpoint of the jump, you attain a vertical height equal to one-quarter of the horizontal distance.

Now, the way I understand the rule, you have to fall or jump down to receive falling damage as it is "per 10' fallen" and if you jump down. If you happens to have a really high jump bonus due to skill ranks, feats, magic and speed, you might end up making a long jump that will propel you up to 20' in the air. The way the rule is written doesn't say that long jump attained height is a falling distance. But I would like to get confirmation as it is not as clear as it should be. You could of course consider making a tumble check to reduce by 10' (or more if you roll very high on tumble) this fall but since you do not jump down, you can't reduce it of another 10'.