drm/i915/dvo: implement get_hw_state

Similar to the sdvo code we poke the dvo encoder whether the output is
active. Safe that dvo encoders are not standardized, so this requires
a new callback into the dvo chip driver.

Hence implement that for all 6 dvo drivers.

v2: With the newly added ns2501 we now have 6 dvo drivers instead of
just 5 ...

Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/dvo_ch7xxx.c

@@ -297,6 +297,18 @@ static void ch7xxx_dpms(struct intel_dvo_device *dvo, bool enable)
 		ch7xxx_writeb(dvo, CH7xxx_PM, CH7xxx_PM_FPD);
 }
 
+static bool ch7xxx_get_hw_state(struct intel_dvo_device *dvo)
+{
+	u8 val;
+
+	ch7xxx_readb(dvo, CH7xxx_PM, &val);
+
+	if (val & CH7xxx_PM_FPD)
+		return false;
+	else
+		return true;
+}
+
 static void ch7xxx_dump_regs(struct intel_dvo_device *dvo)
 {
 	int i;
@@ -326,6 +338,7 @@ struct intel_dvo_dev_ops ch7xxx_ops = {
 	.mode_valid = ch7xxx_mode_valid,
 	.mode_set = ch7xxx_mode_set,
 	.dpms = ch7xxx_dpms,
+	.get_hw_state = ch7xxx_get_hw_state,
 	.dump_regs = ch7xxx_dump_regs,
 	.destroy = ch7xxx_destroy,
 };