From f202e8f3c3f0874a219bf90c8c5cb9caf631be7e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= <ville.syrjala@linux.intel.com>
Date: Wed, 15 Jun 2022 18:14:44 +0300
Subject: drm/i915/bios: Don't parse the DPS panel type when the VBT does not
have it
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Git-commit: 5c9016b2ddb375662aff802d25c96f5483a4e024
Patch-mainline: v6.0-rc1
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225 jsc#PED-2849
Older VBTs don't have all the stuff we've defined for the
LVDS options block (40). In particular we're currently parsing
the DPS panel type bits even though they may not exist, which
could mean we end up flagging the machine as supporting static
DRRS when the VBT declared no such thing.
We don't actually have a clear idea which VBT versions have
which bits so we rely on the block size instead.
Here's a quick list from my VBT stash:
mgm version 108 -> 4 bytes
alv version 120 -> 4 bytes
cst version 134 -> 14 bytes
pnv version 144 -> 14 bytes
cl version 142 -> 16 bytes
ctg version 155 -> 24 bytes
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220615151445.8531-2-ville.syrjala@linux.intel.com
Acked-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
drivers/gpu/drm/i915/display/intel_bios.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c
index ce9731d7059c..f5d360da681d 100644
--- a/drivers/gpu/drm/i915/display/intel_bios.c
+++ b/drivers/gpu/drm/i915/display/intel_bios.c
@@ -759,6 +759,14 @@ parse_panel_options(struct drm_i915_private *i915,
panel->vbt.lvds_dither = lvds_options->pixel_dither;
+ /*
+ * Empirical evidence indicates the block size can be
+ * either 4,14,16,24+ bytes. For older VBTs no clear
+ * relationship between the block size vs. BDB version.
+ */
+ if (get_blocksize(lvds_options) < 16)
+ return;
+
drrs_mode = (lvds_options->dps_panel_type_bits
>> (panel_type * 2)) & MODE_MASK;
/*
--
2.38.1