4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Hans de Goede <hdegoede@xxxxxxxxxx> commit 998d75730b40afc218c059d811869abe9676b305 upstream. 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. Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx> Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx> Link: http://patchwork.freedesktop.org/patch/msgid/1487088758-30050-1-git-send-email-jani.nikula@xxxxxxxxx (cherry picked from commit dfb65e71ea2c1d97ac373cc0587dc60b3307581a) Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/gpu/drm/i915/intel_opregion.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) --- a/drivers/gpu/drm/i915/intel_opregion.c +++ b/drivers/gpu/drm/i915/intel_opregion.c @@ -1031,7 +1031,18 @@ int intel_opregion_setup(struct drm_i915 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;