You have to use input DNA to normalize your qPCR. As you already did ChIP and if you get same intensity bands in your input samples then take same amount of your input DNA as positive control for qPCR. In input DNA, you have basically the fragmented genome and if the number of cells were same in each sample prior to sonication then theoretically you have same number of fragments of promoter of your interest. Therefore, it can be used as positive control.

Good Luck

There are two ways to analyze CHIP-QPCR data. Here is the details:http://zh.invitrogen.com/site/cn/zh/home/Products-and-Services/Applications/epigenetics-noncoding-rna-research/Chromatin-Remodeling/Chromatin-Immunoprecipitation-ChIP/chip-analysis.html