How to set values.yaml of subchart in helmfile

I have created a helmfile to install helm chart of loki-stack and trying to pass values.yaml but I am not able to do so. The following is my helmfile

repositories:
  - name: loki 
    url: https://grafana.github.io/loki/charts

releases:
  - name: loki
    namespace: logs
    chart: loki/loki-stack
    values:
    - "./loki-stack/charts/loki/values.yaml"

The problem might have occurred because Loki is a sub chart of Loki-chart. I have changed the ingress in the above and it does not work. Is there any way so that I can pass the file for variables?