VLV_BLC_PWM_CTL2
ctl2 = intel_de_read(display, VLV_BLC_PWM_CTL2(pipe));
intel_de_rmw(display, VLV_BLC_PWM_CTL2(pipe), BLM_PWM_ENABLE, 0);
ctl2 = intel_de_read(display, VLV_BLC_PWM_CTL2(pipe));
intel_de_write(display, VLV_BLC_PWM_CTL2(pipe), ctl2);
intel_de_write(display, VLV_BLC_PWM_CTL2(pipe), ctl2);
intel_de_posting_read(display, VLV_BLC_PWM_CTL2(pipe));
intel_de_write(display, VLV_BLC_PWM_CTL2(pipe), ctl2 | BLM_PWM_ENABLE);