drm/i915/cnp: Ignore VBT request for know invalid DDC pin.

Let's ignore VBT request if the pin is clearly wrong.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104139
Cc: Kai Heng Feng <kai.heng.feng@canonical.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180123174050.4261-1-rodrigo.vivi@intel.com
Reviewed-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
(cherry picked from commit a8e6f3888b05c1e7b685800a3371ce050720368f)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

1 files changed, 8 insertions, 3 deletions

diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
index 51108ffc28d1..7c6391459d8f 100644
--- a/drivers/gpu/drm/i915/intel_bios.c
+++ b/drivers/gpu/drm/i915/intel_bios.c
@@ -1115,9 +1115,14 @@ static const u8 cnp_ddc_pin_map[] = {
 
 static u8 map_ddc_pin(struct drm_i915_private *dev_priv, u8 vbt_pin)
 {
-        if (HAS_PCH_CNP(dev_priv) &&
-            vbt_pin > 0 && vbt_pin < ARRAY_SIZE(cnp_ddc_pin_map))
-                return cnp_ddc_pin_map[vbt_pin];
+        if (HAS_PCH_CNP(dev_priv)) {
+                if (vbt_pin > 0 && vbt_pin < ARRAY_SIZE(cnp_ddc_pin_map))
+                        return cnp_ddc_pin_map[vbt_pin];
+                if (vbt_pin > GMBUS_PIN_4_CNP) {
+                        DRM_DEBUG_KMS("Ignoring alternate pin: VBT claims DDC pin %d, which is not valid for this platform\n", vbt_pin);
+                        return 0;
+                }
+        }
 
         return vbt_pin;
 }