1. A method comprising: receiving, by a generic row decoder unit, soft information regarding a codeword at an iterative parity check decoder that operates according to a parity check matrix arranged as a plurality of ordered rows, each ordered row corresponding to a parity constraint, and the plurality of ordered rows grouped into a plurality of subsets; performing updates of soft information at the iterative parity check decoder for a particular iteration by sequentially updating the plurality of subsets, one subset at a time using results based on previous subset updates of the particular iteration, each parity constraint in a subset being updated in parallel with the other parity constraints in the same subset; and converging on the codeword after the particular iteration.