[PATCH v1] drivers/i915/intel_bios: Fix parsing backlight BDB data

[Karthikeyan Ramasubramanian]

Starting BDB version 239, hdr_dpcd_refresh_timeout is introduced to
backlight BDB data. Commit 700034566d68 ("drm/i915/bios: Define more BDB
contents") updated the backlight BDB data accordingly. This broke the
parsing of backlight BDB data in VBT for versions 236 - 238 (both
inclusive) and hence the backlight controls are not responding on units
with the concerned BDB version.

backlight_control information has been present in backlight BDB data
from at least BDB version 191 onwards, if not before. Hence this patch
extracts the backlight_control information if the block size of
backlight BDB is >= version 191 backlight BDB block size.
Tested on Chromebooks using Jasperlake SoC (reports bdb->version = 236).
Tested on Chromebooks using Raptorlake SoC (reports bdb->version = 251).

Fixes: 700034566d68 ("drm/i915/bios: Define more BDB contents")
Cc: stable at vger.kernel.org
Cc: Jani Nikula <jani.nikula at intel.com>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Signed-off-by: Karthikeyan Ramasubramanian <kramasub at chromium.org>
---

 drivers/gpu/drm/i915/display/intel_bios.c     | 22 +++++--------------
 drivers/gpu/drm/i915/display/intel_vbt_defs.h |  2 --
 2 files changed, 6 insertions(+), 18 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c
index aa169b0055e97..4ec50903b9e64 100644
--- a/drivers/gpu/drm/i915/display/intel_bios.c
+++ b/drivers/gpu/drm/i915/display/intel_bios.c
@@ -1041,23 +1041,13 @@ parse_lfp_backlight(struct drm_i915_private *i915,
 
 	panel->vbt.backlight.type = INTEL_BACKLIGHT_DISPLAY_DDI;
 	panel->vbt.backlight.controller = 0;
-	if (i915->display.vbt.version >= 191) {
-		size_t exp_size;
+	if (i915->display.vbt.version >= 191 &&
+	    get_blocksize(backlight_data) >= EXP_BDB_LFP_BL_DATA_SIZE_REV_191) {
+		const struct lfp_backlight_control_method *method;
 
-		if (i915->display.vbt.version >= 236)
-			exp_size = sizeof(struct bdb_lfp_backlight_data);
-		else if (i915->display.vbt.version >= 234)
-			exp_size = EXP_BDB_LFP_BL_DATA_SIZE_REV_234;
-		else
-			exp_size = EXP_BDB_LFP_BL_DATA_SIZE_REV_191;
-
-		if (get_blocksize(backlight_data) >= exp_size) {
-			const struct lfp_backlight_control_method *method;
-
-			method = &backlight_data->backlight_control[panel_type];
-			panel->vbt.backlight.type = method->type;
-			panel->vbt.backlight.controller = method->controller;
-		}
+		method = &backlight_data->backlight_control[panel_type];
+		panel->vbt.backlight.type = method->type;
+		panel->vbt.backlight.controller = method->controller;
 	}
 
 	panel->vbt.backlight.pwm_freq_hz = entry->pwm_freq_hz;
diff --git a/drivers/gpu/drm/i915/display/intel_vbt_defs.h b/drivers/gpu/drm/i915/display/intel_vbt_defs.h
index a9f44abfc9fc2..aeea5635a37ff 100644
--- a/drivers/gpu/drm/i915/display/intel_vbt_defs.h
+++ b/drivers/gpu/drm/i915/display/intel_vbt_defs.h
@@ -899,8 +899,6 @@ struct lfp_brightness_level {
 
 #define EXP_BDB_LFP_BL_DATA_SIZE_REV_191 \
 	offsetof(struct bdb_lfp_backlight_data, brightness_level)
-#define EXP_BDB_LFP_BL_DATA_SIZE_REV_234 \
-	offsetof(struct bdb_lfp_backlight_data, brightness_precision_bits)
 
 struct bdb_lfp_backlight_data {
 	u8 entry_size;
-- 
2.44.0.rc0.258.g7320e95886-goog