From: Hans de Goede <hdegoede@xxxxxxxxxx>
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 and on a ACER SW5_017 machine.
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
---
Hans, I'm resending because for some reason our CI didn't pick this
up. Fixed a s/one/on/ typo in the comment while at it.
---
drivers/gpu/drm/i915/intel_opregion.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/intel_opregion.c b/drivers/gpu/drm/i915/intel_opregion.c
index f4429f67a4e3..4a862a358c70 100644
--- a/drivers/gpu/drm/i915/intel_opregion.c
+++ b/drivers/gpu/drm/i915/intel_opregion.c
@@ -982,7 +982,18 @@ 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;
+ /*
+ * The VBT specification says that if the ASLE ext
+ * mailbox is not used its area is reserved, but
+ * on some CHT boards the VBT extends into the
+ * ASLE ext area. Allow this even though it is
+ * against the spec, so we do not end up rejecting
+ * the VBT on those boards (and end up not finding the
+ * LCD panel because of this).
+ */
+ 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;
--
2.1.4
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