drm/i915: LPT:LP needs port A HPD enabled in both north and south

If the CPU and PCH are on the same package we must enabled the port A
HPD also in the south hotplug register. To identify the package type
we simply look at the PCH type: LPT-H means separate package, and
LPT-LP means multi chip package (MCP).

v2: Add comment and pimp commit message
Reviewed-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_irq.c

@@ -3131,6 +3131,12 @@ static void ibx_hpd_irq_setup(struct drm_device *dev)
 	hotplug |= PORTD_HOTPLUG_ENABLE | PORTD_PULSE_DURATION_2ms;
 	hotplug |= PORTC_HOTPLUG_ENABLE | PORTC_PULSE_DURATION_2ms;
 	hotplug |= PORTB_HOTPLUG_ENABLE | PORTB_PULSE_DURATION_2ms;
+	/*
+	 * When CPU and PCH are on the same package, port A
+	 * HPD must be enabled in both north and south.
+	 */
+	if (HAS_PCH_LPT_LP(dev))
+		hotplug |= PORTA_HOTPLUG_ENABLE;
 	I915_WRITE(PCH_PORT_HOTPLUG, hotplug);
 }