\begin{tikzpicture}[trim axis left, trim axis right]
  \begin{axis}[
    semithick,
    width = 12cm,
    height = 4cm,
    xmode=log,
    %ymin = 0,
    % scaled y ticks=base 10:0,
    xlabel = fixed point tolerance,
    ylabel style={align=center}, ylabel = multigrid\\iterations, % (multigrid steps)
    extra x ticks       = 1e-5,
    extra x tick labels = { time-stepping\\tolerance },
    extra x tick style  = { align=center, grid = major, ticklabel pos=right }
    ]
    \addplot[mark=+] table[col sep=comma, y=mg] {generated/fpi-data.csv};
  \end{axis}
\end{tikzpicture}