linux-kernel - [PATCH 4.9 56/63] drm/i915: Fix not finding the VBT when it overlaps with OPREGION_ASLE

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Message-Id: <20170313083417.744571953@linuxfoundation.org>
Date:   Mon, 13 Mar 2017 16:39:43 +0800
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Hans de Goede <hdegoede@...hat.com>,
        Jani Nikula <jani.nikula@...el.com>
Subject: [PATCH 4.9 56/63] drm/i915: Fix not finding the VBT when it overlaps with OPREGION_ASLE_EXT

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

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

From: Hans de Goede <hdegoede@...hat.com>

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@...hat.com>
Signed-off-by: Jani Nikula <jani.nikula@...el.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1487088758-30050-1-git-send-email-jani.nikula@intel.com
(cherry picked from commit dfb65e71ea2c1d97ac373cc0587dc60b3307581a)
Signed-off-by: Jani Nikula <jani.nikula@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 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;