drm/i915/bios: Fix parsing backlight BDB data

Starting BDB version 239, hdr_dpcd_refresh_timeout is introduced to
backlight BDB data. Commit 70003456 ("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 for BDB version 191 or newer.
Tested on Chromebooks using Jasperlake SoC (reports bdb->version = 236).
Tested on Chromebooks using Raptorlake SoC (reports bdb->version = 251).

v2: removed checking the block size of the backlight BDB data
    [vsyrjala: this is completely safe thanks to commit e163cfb4
     ("drm/i915/bios: Make copies of VBT data blocks")]

Fixes: 70003456 ("drm/i915/bios: Define more BDB contents")
Cc: stable@vger.kernel.org
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Karthikeyan Ramasubramanian <kramasub@chromium.org>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240221180622.v2.1.I0690aa3e96a83a43b3fc33f50395d334b2981826@changeidSigned-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

drivers/gpu/drm/i915/display/intel_bios.c

@@ -1037,23 +1037,12 @@ 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 >= 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;
 	}
-	}
 
 	panel->vbt.backlight.pwm_freq_hz = entry->pwm_freq_hz;
 	panel->vbt.backlight.active_low_pwm = entry->active_low_pwm;

drivers/gpu/drm/i915/display/intel_vbt_defs.h

@@ -899,11 +899,6 @@ struct lfp_brightness_level {
 	u16 reserved;
 } __packed;
 
-#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;
 	struct lfp_backlight_data_entry data[16];