diff --git a/consensus/clique/clique.go b/consensus/clique/clique.go
index 1b693f75b3..31fe4d905e 100644
--- a/consensus/clique/clique.go
+++ b/consensus/clique/clique.go
@@ -652,7 +652,9 @@ func (c *Clique) Seal(chain consensus.ChainReader, block *types.Block, stop <-ch
 	return block.WithSeal(header), nil
 }
 
-// CalcDifficulty is the difficulty adjustment algorithm. It returns the difficulty that a new block should have.
+// CalcDifficulty is the difficulty adjustment algorithm. It returns the difficulty
+// that a new block should have based on the previous blocks in the chain and the
+// current signer.
 func (c *Clique) CalcDifficulty(chain consensus.ChainReader, time uint64, parent *types.Header) *big.Int {
 	snap, err := c.snapshot(chain, parent.Number.Uint64(), parent.Hash(), nil)
 	if err != nil {
@@ -661,7 +663,9 @@ func (c *Clique) CalcDifficulty(chain consensus.ChainReader, time uint64, parent
 	return CalcDifficulty(snap, c.signer)
 }
 
-// CalcDifficulty returns block difficulty according to local signer is the inturn signer or not.
+// CalcDifficulty is the difficulty adjustment algorithm. It returns the difficulty
+// that a new block should have based on the previous blocks in the chain and the
+// current signer.
 func CalcDifficulty(snap *Snapshot, signer common.Address) *big.Int {
 	if snap.inturn(snap.Number+1, signer) {
 		return new(big.Int).Set(diffInTurn)
diff --git a/consensus/ethash/consensus.go b/consensus/ethash/consensus.go
index 34f73d1f42..ab4acf8ec2 100644
--- a/consensus/ethash/consensus.go
+++ b/consensus/ethash/consensus.go
@@ -291,7 +291,9 @@ func (ethash *Ethash) CalcDifficulty(chain consensus.ChainReader, time uint64, p
 	return CalcDifficulty(chain.Config(), time, parent)
 }
 
-// CalcDifficulty returns block difficulty according to the parent block's time and difficulty.
+// CalcDifficulty is the difficulty adjustment algorithm. It returns
+// the difficulty that a new block should have when created at time
+// given the parent block's time and difficulty.
 func CalcDifficulty(config *params.ChainConfig, time uint64, parent *types.Header) *big.Int {
 	next := new(big.Int).Add(parent.Number, big1)
 	switch {
diff --git a/core/chain_makers.go b/core/chain_makers.go
index d107add59c..0e5e3791e5 100644
--- a/core/chain_makers.go
+++ b/core/chain_makers.go
@@ -164,8 +164,11 @@ func GenerateChain(config *params.ChainConfig, parent *types.Block, engine conse
 	}
 	blocks, receipts := make(types.Blocks, n), make([]types.Receipts, n)
 	genblock := func(i int, parent *types.Block, statedb *state.StateDB) (*types.Block, types.Receipts) {
+		// TODO(karalabe): This is needed for clique, which depends on multiple blocks.
+		// It's nonetheless ugly to spin up a blockchain here. Get rid of this somehow.
 		blockchain, _ := NewBlockChain(db, config, engine, vm.Config{})
 		defer blockchain.Stop()
+
 		b := &BlockGen{i: i, parent: parent, chain: blocks, chainReader: blockchain, statedb: statedb, config: config, engine: engine}
 		b.header = makeHeader(b.chainReader, parent, statedb, b.engine)