[PATCH] drm/i915: Fix not finding the VBT when it overlaps with OPREGION_ASLE_EXT

[Hans de Goede]

If there is no OPREGION_ASLE_EXT then a VBT stored in mailbox #4 may
use the ASLE_EXT parts of the opregion. Adjust the vbt_size calculation
for a vbt in mailbox #4 for this.

This fixes the driver not finding the VBT on a jumper ezpad mini3
cherrytrail tablet.

Cc: stable at vger.kernel.org
Signed-off-by: Hans de Goede <hdegoede at redhat.com>
---
Note even with this fixed the panel still does not work with 4.9,
but it does with drm-intel-next-queued :) I believe the missing bit in
4.9 is the "drm/915: Parsing the missed out DTD fields from the VBT"
commit, but I've not verified this.
---
 drivers/gpu/drm/i915/intel_opregion.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_opregion.c b/drivers/gpu/drm/i915/intel_opregion.c
index f4429f6..eff35ae 100644
--- a/drivers/gpu/drm/i915/intel_opregion.c
+++ b/drivers/gpu/drm/i915/intel_opregion.c
@@ -982,7 +982,9 @@ int intel_opregion_setup(struct drm_i915_private *dev_priv)
 			opregion->vbt_size = vbt_size;
 		} else {
 			vbt = base + OPREGION_VBT_OFFSET;
-			vbt_size = OPREGION_ASLE_EXT_OFFSET - OPREGION_VBT_OFFSET;
+			vbt_size = (mboxes & MBOX_ASLE_EXT) ?
+				OPREGION_ASLE_EXT_OFFSET : OPREGION_SIZE;
+			vbt_size -= OPREGION_VBT_OFFSET;
 			if (intel_bios_is_valid_vbt(vbt, vbt_size)) {
 				DRM_DEBUG_KMS("Found valid VBT in ACPI OpRegion (Mailbox #4)\n");
 				opregion->vbt = vbt;
-- 
2.9.3