The calculation of the frac variable is based solely on integers and therefore results in the fractional part being either 0 or 1. In the original code from RaspberryPi this is mitigated by casting the nominator to a double. This works for most cases, but fails when q is very small because of the quantization introduced by item being an integer. Fix both issues by doing the full calculation in double and remove the should_fail tag. Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>