5 QSPI code supports single, dual, quad lanes.
6 also supports both SDR and DDR modes.
8 * <https://bitbucket.org/casl/c-class/src/3fba75dfbd0c64815eb8ec6dc965666812c44bae/src/peripherals/qspi/?at=master>
9 * <https://gitlab.raptorengineering.com/kestrel-collaboration/kestrel-litex/litex-boards/-/blob/a9ed41b6068236de7ce5b5ad0e80353be22817ca/litex_boards/targets/versa_ecp5.py#L43>