here is the code I used:
mxc_request_iomux(MX31_PIN_CSI_D12, OUTPUTCONFIG_GPIO, INPUTCONFIG_GPIO);
mxc_iomux_set_pad(MX31_PIN_CSI_D12,
(PAD_CTL_PKE_NONE | PAD_CTL_SRE_SLOW));
mxc_set_gpio_direction(MX31_PIN_CSI_D12, 0);
mxc_set_gpio_dataout(MX31_PIN_CSI_D12, 0);
the important stuff was setting the direction, then the dataout.