[PATCH 4.15 107/168] drm/i915/cnp: Ignore VBT request for know invalid DDC pin.

[Greg Kroah-Hartman]

4.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>

commit f24c606c21a8cb6f75adc20edcd80b6d851991bf upstream.

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@xxxxxxxxxxxxx>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20180123174050.4261-1-rodrigo.vivi@xxxxxxxxx
Reviewed-by: Radhakrishna Sripada <radhakrishna.sripada@xxxxxxxxx>
(cherry picked from commit a8e6f3888b05c1e7b685800a3371ce050720368f)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/gpu/drm/i915/intel_bios.c |   11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

--- 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;
 }