VLV_BLC_PWM_CTL
ctl = intel_de_read(display, VLV_BLC_PWM_CTL(pipe));
return intel_de_read(display, VLV_BLC_PWM_CTL(pipe)) & BACKLIGHT_DUTY_CYCLE_MASK;
tmp = intel_de_read(display, VLV_BLC_PWM_CTL(pipe)) & ~BACKLIGHT_DUTY_CYCLE_MASK;
intel_de_write(display, VLV_BLC_PWM_CTL(pipe), tmp | level);
intel_de_write(display, VLV_BLC_PWM_CTL(pipe), ctl);