  We investigate an inflationary model involving a gauge singlet scalar and
fermionic dark matter. The mixing between the singlet scalar and the Higgs
boson provides a portal to dark matter. The inflaton could either be the Higgs
boson or the singlet scalar, and slow roll inflation is realized via its
non-minimal coupling to gravity. In this setup, the effective scalar potential
is stabilized by the mixing between two scalars and coupling with dark matter.
We study constraints from collider searches, relic density and direct
detection, and find that dark matter mass should be around half the mass of
either the Higgs boson or singlet scalar. Using the renormalization group
equation improved scalar potential and putting all the constraints together, we
show that the inflationary observables $n_s-r$ are consistent with current
Planck data.
