How to do a stacked waterfall chart

I have 2 columns one column P with P1&P2 values and another with values mi 

p    | mi    |

-----------|

P1  | null  |

P2  |null   |

P1  |mi     |

P2  |mi     |

P1  |null   |

P2  |mi     |

P1  |mi     |

..................... so on

and i want it to be like P1+P2 as a single lengend and mi as another legend for waterfall chart

I want to create a stacked waterfall chart using these two column with count values in y axis and P1, P2 ,Total in x axis

Mi to be stacked on top of P1 and P2 in waterfall chart

Do i have to merge p and mi and create a new column to create a waterfall chart