VLV_BLC_PWM_CTL2
ctl2 = I915_READ(VLV_BLC_PWM_CTL2(pipe));
tmp = I915_READ(VLV_BLC_PWM_CTL2(pipe));
I915_WRITE(VLV_BLC_PWM_CTL2(pipe), tmp & ~BLM_PWM_ENABLE);
ctl2 = I915_READ(VLV_BLC_PWM_CTL2(pipe));
I915_WRITE(VLV_BLC_PWM_CTL2(pipe), ctl2);
I915_WRITE(VLV_BLC_PWM_CTL2(pipe), ctl2);
POSTING_READ(VLV_BLC_PWM_CTL2(pipe));
I915_WRITE(VLV_BLC_PWM_CTL2(pipe), ctl2 | BLM_PWM_ENABLE);