drivers/gpu/drm/i915/intel_bios.c

/*
 * Copyright © 2006 Intel Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 * Authors:
 *    Eric Anholt <eric@anholt.net>
 *
 */

#include <drm/drm_dp_helper.h>
#include <drm/drmP.h>
#include <drm/i915_drm.h>
#include "i915_drv.h"
#include "intel_bios.h"

/**
 * DOC: Video BIOS Table (VBT)
 *
 * The Video BIOS Table, or VBT, provides platform and board specific
 * configuration information to the driver that is not discoverable or available
 * through other means. The configuration is mostly related to display
 * hardware. The VBT is available via the ACPI OpRegion or, on older systems, in
 * the PCI ROM.
 *
 * The VBT consists of a VBT Header (defined as &struct vbt_header), a BDB
 * Header (&struct bdb_header), and a number of BIOS Data Blocks (BDB) that
 * contain the actual configuration information. The VBT Header, and thus the
 * VBT, begins with "$VBT" signature. The VBT Header contains the offset of the
 * BDB Header. The data blocks are concatenated after the BDB Header. The data
 * blocks have a 1-byte Block ID, 2-byte Block Size, and Block Size bytes of
 * data. (Block 53, the MIPI Sequence Block is an exception.)
 *
 * The driver parses the VBT during load. The relevant information is stored in
 * driver private data for ease of use, and the actual VBT is not read after
 * that.
 */

#define	SLAVE_ADDR1	0x70
#define	SLAVE_ADDR2	0x72

static int panel_type;

/* Get BDB block size given a pointer to Block ID. */
static u32 _get_blocksize(const u8 *block_base)
{
	/* The MIPI Sequence Block v3+ has a separate size field. */
	if (*block_base == BDB_MIPI_SEQUENCE && *(block_base + 3) >= 3)
		return *((const u32 *)(block_base + 4));
	else
		return *((const u16 *)(block_base + 1));
}

/* Get BDB block size give a pointer to data after Block ID and Block Size. */
static u32 get_blocksize(const void *block_data)
{
	return _get_blocksize(block_data - 3);
}

static const void *
find_section(const void *_bdb, int section_id)
{
	const struct bdb_header *bdb = _bdb;
	const u8 *base = _bdb;
	int index = 0;
	u32 total, current_size;
	u8 current_id;

	/* skip to first section */
	index += bdb->header_size;
	total = bdb->bdb_size;

	/* walk the sections looking for section_id */
	while (index + 3 < total) {
		current_id = *(base + index);
		current_size = _get_blocksize(base + index);
		index += 3;

		if (index + current_size > total)
			return NULL;

		if (current_id == section_id)
			return base + index;

		index += current_size;
	}

	return NULL;
}

static void
fill_detail_timing_data(struct drm_display_mode *panel_fixed_mode,
			const struct lvds_dvo_timing *dvo_timing)
{
	panel_fixed_mode->hdisplay = (dvo_timing->hactive_hi << 8) |
		dvo_timing->hactive_lo;
	panel_fixed_mode->hsync_start = panel_fixed_mode->hdisplay +
		((dvo_timing->hsync_off_hi << 8) | dvo_timing->hsync_off_lo);
	panel_fixed_mode->hsync_end = panel_fixed_mode->hsync_start +
		dvo_timing->hsync_pulse_width;
	panel_fixed_mode->htotal = panel_fixed_mode->hdisplay +
		((dvo_timing->hblank_hi << 8) | dvo_timing->hblank_lo);

	panel_fixed_mode->vdisplay = (dvo_timing->vactive_hi << 8) |
		dvo_timing->vactive_lo;
	panel_fixed_mode->vsync_start = panel_fixed_mode->vdisplay +
		dvo_timing->vsync_off;
	panel_fixed_mode->vsync_end = panel_fixed_mode->vsync_start +
		dvo_timing->vsync_pulse_width;
	panel_fixed_mode->vtotal = panel_fixed_mode->vdisplay +
		((dvo_timing->vblank_hi << 8) | dvo_timing->vblank_lo);
	panel_fixed_mode->clock = dvo_timing->clock * 10;
	panel_fixed_mode->type = DRM_MODE_TYPE_PREFERRED;

	if (dvo_timing->hsync_positive)
		panel_fixed_mode->flags |= DRM_MODE_FLAG_PHSYNC;
	else
		panel_fixed_mode->flags |= DRM_MODE_FLAG_NHSYNC;

	if (dvo_timing->vsync_positive)
		panel_fixed_mode->flags |= DRM_MODE_FLAG_PVSYNC;
	else
		panel_fixed_mode->flags |= DRM_MODE_FLAG_NVSYNC;

	/* Some VBTs have bogus h/vtotal values */
	if (panel_fixed_mode->hsync_end > panel_fixed_mode->htotal)
		panel_fixed_mode->htotal = panel_fixed_mode->hsync_end + 1;
	if (panel_fixed_mode->vsync_end > panel_fixed_mode->vtotal)
		panel_fixed_mode->vtotal = panel_fixed_mode->vsync_end + 1;

	drm_mode_set_name(panel_fixed_mode);
}

static const struct lvds_dvo_timing *
get_lvds_dvo_timing(const struct bdb_lvds_lfp_data *lvds_lfp_data,
		    const struct bdb_lvds_lfp_data_ptrs *lvds_lfp_data_ptrs,
		    int index)
{
	/*
	 * the size of fp_timing varies on the different platform.
	 * So calculate the DVO timing relative offset in LVDS data
	 * entry to get the DVO timing entry
	 */

	int lfp_data_size =
		lvds_lfp_data_ptrs->ptr[1].dvo_timing_offset -
		lvds_lfp_data_ptrs->ptr[0].dvo_timing_offset;
	int dvo_timing_offset =
		lvds_lfp_data_ptrs->ptr[0].dvo_timing_offset -
		lvds_lfp_data_ptrs->ptr[0].fp_timing_offset;
	char *entry = (char *)lvds_lfp_data->data + lfp_data_size * index;

	return (struct lvds_dvo_timing *)(entry + dvo_timing_offset);
}

/* get lvds_fp_timing entry
 * this function may return NULL if the corresponding entry is invalid
 */
static const struct lvds_fp_timing *
get_lvds_fp_timing(const struct bdb_header *bdb,
		   const struct bdb_lvds_lfp_data *data,
		   const struct bdb_lvds_lfp_data_ptrs *ptrs,
		   int index)
{
	size_t data_ofs = (const u8 *)data - (const u8 *)bdb;
	u16 data_size = ((const u16 *)data)[-1]; /* stored in header */
	size_t ofs;

	if (index >= ARRAY_SIZE(ptrs->ptr))
		return NULL;
	ofs = ptrs->ptr[index].fp_timing_offset;
	if (ofs < data_ofs ||
	    ofs + sizeof(struct lvds_fp_timing) > data_ofs + data_size)
		return NULL;
	return (const struct lvds_fp_timing *)((const u8 *)bdb + ofs);
}

/* Try to find integrated panel data */
static void
parse_lfp_panel_data(struct drm_i915_private *dev_priv,
		     const struct bdb_header *bdb)
{
	const struct bdb_lvds_options *lvds_options;
	const struct bdb_lvds_lfp_data *lvds_lfp_data;
	const struct bdb_lvds_lfp_data_ptrs *lvds_lfp_data_ptrs;
	const struct lvds_dvo_timing *panel_dvo_timing;
	const struct lvds_fp_timing *fp_timing;
	struct drm_display_mode *panel_fixed_mode;
	int drrs_mode;

	lvds_options = find_section(bdb, BDB_LVDS_OPTIONS);
	if (!lvds_options)
		return;

	dev_priv->vbt.lvds_dither = lvds_options->pixel_dither;
	if (lvds_options->panel_type == 0xff)
		return;

	panel_type = lvds_options->panel_type;

	drrs_mode = (lvds_options->dps_panel_type_bits
				>> (panel_type * 2)) & MODE_MASK;
	/*
	 * VBT has static DRRS = 0 and seamless DRRS = 2.
	 * The below piece of code is required to adjust vbt.drrs_type
	 * to match the enum drrs_support_type.
	 */
	switch (drrs_mode) {
	case 0:
		dev_priv->vbt.drrs_type = STATIC_DRRS_SUPPORT;
		DRM_DEBUG_KMS("DRRS supported mode is static\n");
		break;
	case 2:
		dev_priv->vbt.drrs_type = SEAMLESS_DRRS_SUPPORT;
		DRM_DEBUG_KMS("DRRS supported mode is seamless\n");
		break;
	default:
		dev_priv->vbt.drrs_type = DRRS_NOT_SUPPORTED;
		DRM_DEBUG_KMS("DRRS not supported (VBT input)\n");
		break;
	}

	lvds_lfp_data = find_section(bdb, BDB_LVDS_LFP_DATA);
	if (!lvds_lfp_data)
		return;

	lvds_lfp_data_ptrs = find_section(bdb, BDB_LVDS_LFP_DATA_PTRS);
	if (!lvds_lfp_data_ptrs)
		return;

	dev_priv->vbt.lvds_vbt = 1;

	panel_dvo_timing = get_lvds_dvo_timing(lvds_lfp_data,
					       lvds_lfp_data_ptrs,
					       lvds_options->panel_type);

	panel_fixed_mode = kzalloc(sizeof(*panel_fixed_mode), GFP_KERNEL);
	if (!panel_fixed_mode)
		return;

	fill_detail_timing_data(panel_fixed_mode, panel_dvo_timing);

	dev_priv->vbt.lfp_lvds_vbt_mode = panel_fixed_mode;

	DRM_DEBUG_KMS("Found panel mode in BIOS VBT tables:\n");
	drm_mode_debug_printmodeline(panel_fixed_mode);

	fp_timing = get_lvds_fp_timing(bdb, lvds_lfp_data,
				       lvds_lfp_data_ptrs,
				       lvds_options->panel_type);
	if (fp_timing) {
		/* check the resolution, just to be sure */
		if (fp_timing->x_res == panel_fixed_mode->hdisplay &&
		    fp_timing->y_res == panel_fixed_mode->vdisplay) {
			dev_priv->vbt.bios_lvds_val = fp_timing->lvds_reg_val;
			DRM_DEBUG_KMS("VBT initial LVDS value %x\n",
				      dev_priv->vbt.bios_lvds_val);
		}
	}
}

static void
parse_lfp_backlight(struct drm_i915_private *dev_priv,
		    const struct bdb_header *bdb)
{
	const struct bdb_lfp_backlight_data *backlight_data;
	const struct bdb_lfp_backlight_data_entry *entry;

	backlight_data = find_section(bdb, BDB_LVDS_BACKLIGHT);
	if (!backlight_data)
		return;

	if (backlight_data->entry_size != sizeof(backlight_data->data[0])) {
		DRM_DEBUG_KMS("Unsupported backlight data entry size %u\n",
			      backlight_data->entry_size);
		return;
	}

	entry = &backlight_data->data[panel_type];

	dev_priv->vbt.backlight.present = entry->type == BDB_BACKLIGHT_TYPE_PWM;
	if (!dev_priv->vbt.backlight.present) {
		DRM_DEBUG_KMS("PWM backlight not present in VBT (type %u)\n",
			      entry->type);
		return;
	}

	dev_priv->vbt.backlight.pwm_freq_hz = entry->pwm_freq_hz;
	dev_priv->vbt.backlight.active_low_pwm = entry->active_low_pwm;
	dev_priv->vbt.backlight.min_brightness = entry->min_brightness;
	DRM_DEBUG_KMS("VBT backlight PWM modulation frequency %u Hz, "
		      "active %s, min brightness %u, level %u\n",
		      dev_priv->vbt.backlight.pwm_freq_hz,
		      dev_priv->vbt.backlight.active_low_pwm ? "low" : "high",
		      dev_priv->vbt.backlight.min_brightness,
		      backlight_data->level[panel_type]);
}

/* Try to find sdvo panel data */
static void
parse_sdvo_panel_data(struct drm_i915_private *dev_priv,
		      const struct bdb_header *bdb)
{
	const struct lvds_dvo_timing *dvo_timing;
	struct drm_display_mode *panel_fixed_mode;
	int index;

	index = i915.vbt_sdvo_panel_type;
	if (index == -2) {
		DRM_DEBUG_KMS("Ignore SDVO panel mode from BIOS VBT tables.\n");
		return;
	}

	if (index == -1) {
		const struct bdb_sdvo_lvds_options *sdvo_lvds_options;

		sdvo_lvds_options = find_section(bdb, BDB_SDVO_LVDS_OPTIONS);
		if (!sdvo_lvds_options)
			return;

		index = sdvo_lvds_options->panel_type;
	}

	dvo_timing = find_section(bdb, BDB_SDVO_PANEL_DTDS);
	if (!dvo_timing)
		return;

	panel_fixed_mode = kzalloc(sizeof(*panel_fixed_mode), GFP_KERNEL);
	if (!panel_fixed_mode)
		return;

	fill_detail_timing_data(panel_fixed_mode, dvo_timing + index);

	dev_priv->vbt.sdvo_lvds_vbt_mode = panel_fixed_mode;

	DRM_DEBUG_KMS("Found SDVO panel mode in BIOS VBT tables:\n");
	drm_mode_debug_printmodeline(panel_fixed_mode);
}

static int intel_bios_ssc_frequency(struct drm_i915_private *dev_priv,
				    bool alternate)
{
	switch (INTEL_INFO(dev_priv)->gen) {
	case 2:
		return alternate ? 66667 : 48000;
	case 3:
	case 4:
		return alternate ? 100000 : 96000;
	default:
		return alternate ? 100000 : 120000;
	}
}

static void
parse_general_features(struct drm_i915_private *dev_priv,
		       const struct bdb_header *bdb)
{
	const struct bdb_general_features *general;

	general = find_section(bdb, BDB_GENERAL_FEATURES);
	if (!general)
		return;

	dev_priv->vbt.int_tv_support = general->int_tv_support;
	/* int_crt_support can't be trusted on earlier platforms */
	if (bdb->version >= 155 &&
	    (HAS_DDI(dev_priv) || IS_VALLEYVIEW(dev_priv)))
		dev_priv->vbt.int_crt_support = general->int_crt_support;
	dev_priv->vbt.lvds_use_ssc = general->enable_ssc;
	dev_priv->vbt.lvds_ssc_freq =
		intel_bios_ssc_frequency(dev_priv, general->ssc_freq);
	dev_priv->vbt.display_clock_mode = general->display_clock_mode;
	dev_priv->vbt.fdi_rx_polarity_inverted = general->fdi_rx_polarity_inverted;
	DRM_DEBUG_KMS("BDB_GENERAL_FEATURES int_tv_support %d int_crt_support %d lvds_use_ssc %d lvds_ssc_freq %d display_clock_mode %d fdi_rx_polarity_inverted %d\n",
		      dev_priv->vbt.int_tv_support,
		      dev_priv->vbt.int_crt_support,
		      dev_priv->vbt.lvds_use_ssc,
		      dev_priv->vbt.lvds_ssc_freq,
		      dev_priv->vbt.display_clock_mode,
		      dev_priv->vbt.fdi_rx_polarity_inverted);
}

static void
parse_general_definitions(struct drm_i915_private *dev_priv,
			  const struct bdb_header *bdb)
{
	const struct bdb_general_definitions *general;

	general = find_section(bdb, BDB_GENERAL_DEFINITIONS);
	if (general) {
		u16 block_size = get_blocksize(general);
		if (block_size >= sizeof(*general)) {
			int bus_pin = general->crt_ddc_gmbus_pin;
			DRM_DEBUG_KMS("crt_ddc_bus_pin: %d\n", bus_pin);
			if (intel_gmbus_is_valid_pin(dev_priv, bus_pin))
				dev_priv->vbt.crt_ddc_pin = bus_pin;
		} else {
			DRM_DEBUG_KMS("BDB_GD too small (%d). Invalid.\n",
				      block_size);
		}
	}
}

static const union child_device_config *
child_device_ptr(const struct bdb_general_definitions *p_defs, int i)
{
	return (const void *) &p_defs->devices[i * p_defs->child_dev_size];
}

static void
parse_sdvo_device_mapping(struct drm_i915_private *dev_priv,
			  const struct bdb_header *bdb)
{
	struct sdvo_device_mapping *p_mapping;
	const struct bdb_general_definitions *p_defs;
	const struct old_child_dev_config *child; /* legacy */
	int i, child_device_num, count;
	u16	block_size;

	p_defs = find_section(bdb, BDB_GENERAL_DEFINITIONS);
	if (!p_defs) {
		DRM_DEBUG_KMS("No general definition block is found, unable to construct sdvo mapping.\n");
		return;
	}

	/*
	 * Only parse SDVO mappings when the general definitions block child
	 * device size matches that of the *legacy* child device config
	 * struct. Thus, SDVO mapping will be skipped for newer VBT.
	 */
	if (p_defs->child_dev_size != sizeof(*child)) {
		DRM_DEBUG_KMS("Unsupported child device size for SDVO mapping.\n");
		return;
	}
	/* get the block size of general definitions */
	block_size = get_blocksize(p_defs);
	/* get the number of child device */
	child_device_num = (block_size - sizeof(*p_defs)) /
		p_defs->child_dev_size;
	count = 0;
	for (i = 0; i < child_device_num; i++) {
		child = &child_device_ptr(p_defs, i)->old;
		if (!child->device_type) {
			/* skip the device block if device type is invalid */
			continue;
		}
		if (child->slave_addr != SLAVE_ADDR1 &&
		    child->slave_addr != SLAVE_ADDR2) {
			/*
			 * If the slave address is neither 0x70 nor 0x72,
			 * it is not a SDVO device. Skip it.
			 */
			continue;
		}
		if (child->dvo_port != DEVICE_PORT_DVOB &&
		    child->dvo_port != DEVICE_PORT_DVOC) {
			/* skip the incorrect SDVO port */
			DRM_DEBUG_KMS("Incorrect SDVO port. Skip it\n");
			continue;
		}
		DRM_DEBUG_KMS("the SDVO device with slave addr %2x is found on"
			      " %s port\n",
			      child->slave_addr,
			      (child->dvo_port == DEVICE_PORT_DVOB) ?
			      "SDVOB" : "SDVOC");
		p_mapping = &(dev_priv->sdvo_mappings[child->dvo_port - 1]);
		if (!p_mapping->initialized) {
			p_mapping->dvo_port = child->dvo_port;
			p_mapping->slave_addr = child->slave_addr;
			p_mapping->dvo_wiring = child->dvo_wiring;
			p_mapping->ddc_pin = child->ddc_pin;
			p_mapping->i2c_pin = child->i2c_pin;
			p_mapping->initialized = 1;
			DRM_DEBUG_KMS("SDVO device: dvo=%x, addr=%x, wiring=%d, ddc_pin=%d, i2c_pin=%d\n",
				      p_mapping->dvo_port,
				      p_mapping->slave_addr,
				      p_mapping->dvo_wiring,
				      p_mapping->ddc_pin,
				      p_mapping->i2c_pin);
		} else {
			DRM_DEBUG_KMS("Maybe one SDVO port is shared by "
					 "two SDVO device.\n");
		}
		if (child->slave2_addr) {
			/* Maybe this is a SDVO device with multiple inputs */
			/* And the mapping info is not added */
			DRM_DEBUG_KMS("there exists the slave2_addr. Maybe this"
				" is a SDVO device with multiple inputs.\n");
		}
		count++;
	}

	if (!count) {
		/* No SDVO device info is found */
		DRM_DEBUG_KMS("No SDVO device info is found in VBT\n");
	}
	return;
}

static void
parse_driver_features(struct drm_i915_private *dev_priv,
		      const struct bdb_header *bdb)
{
	const struct bdb_driver_features *driver;

	driver = find_section(bdb, BDB_DRIVER_FEATURES);
	if (!driver)
		return;

	if (driver->lvds_config == BDB_DRIVER_FEATURE_EDP)
		dev_priv->vbt.edp_support = 1;

	if (driver->dual_frequency)
		dev_priv->render_reclock_avail = true;

	DRM_DEBUG_KMS("DRRS State Enabled:%d\n", driver->drrs_enabled);
	/*
	 * If DRRS is not supported, drrs_type has to be set to 0.
	 * This is because, VBT is configured in such a way that
	 * static DRRS is 0 and DRRS not supported is represented by
	 * driver->drrs_enabled=false
	 */
	if (!driver->drrs_enabled)
		dev_priv->vbt.drrs_type = DRRS_NOT_SUPPORTED;
}

static void
parse_edp(struct drm_i915_private *dev_priv, const struct bdb_header *bdb)
{
	const struct bdb_edp *edp;
	const struct edp_power_seq *edp_pps;
	const struct edp_link_params *edp_link_params;

	edp = find_section(bdb, BDB_EDP);
	if (!edp) {
		if (dev_priv->vbt.edp_support)
			DRM_DEBUG_KMS("No eDP BDB found but eDP panel supported.\n");
		return;
	}

	switch ((edp->color_depth >> (panel_type * 2)) & 3) {
	case EDP_18BPP:
		dev_priv->vbt.edp_bpp = 18;
		break;
	case EDP_24BPP:
		dev_priv->vbt.edp_bpp = 24;
		break;
	case EDP_30BPP:
		dev_priv->vbt.edp_bpp = 30;
		break;
	}

	/* Get the eDP sequencing and link info */
	edp_pps = &edp->power_seqs[panel_type];
	edp_link_params = &edp->link_params[panel_type];

	dev_priv->vbt.edp_pps = *edp_pps;

	switch (edp_link_params->rate) {
	case EDP_RATE_1_62:
		dev_priv->vbt.edp_rate = DP_LINK_BW_1_62;
		break;
	case EDP_RATE_2_7:
		dev_priv->vbt.edp_rate = DP_LINK_BW_2_7;
		break;
	default:
		DRM_DEBUG_KMS("VBT has unknown eDP link rate value %u\n",
			      edp_link_params->rate);
		break;
	}

	switch (edp_link_params->lanes) {
	case EDP_LANE_1:
		dev_priv->vbt.edp_lanes = 1;
		break;
	case EDP_LANE_2:
		dev_priv->vbt.edp_lanes = 2;
		break;
	case EDP_LANE_4:
		dev_priv->vbt.edp_lanes = 4;
		break;
	default:
		DRM_DEBUG_KMS("VBT has unknown eDP lane count value %u\n",
			      edp_link_params->lanes);
		break;
	}

	switch (edp_link_params->preemphasis) {
	case EDP_PREEMPHASIS_NONE:
		dev_priv->vbt.edp_preemphasis = DP_TRAIN_PRE_EMPH_LEVEL_0;
		break;
	case EDP_PREEMPHASIS_3_5dB:
		dev_priv->vbt.edp_preemphasis = DP_TRAIN_PRE_EMPH_LEVEL_1;
		break;
	case EDP_PREEMPHASIS_6dB:
		dev_priv->vbt.edp_preemphasis = DP_TRAIN_PRE_EMPH_LEVEL_2;
		break;
	case EDP_PREEMPHASIS_9_5dB:
		dev_priv->vbt.edp_preemphasis = DP_TRAIN_PRE_EMPH_LEVEL_3;
		break;
	default:
		DRM_DEBUG_KMS("VBT has unknown eDP pre-emphasis value %u\n",
			      edp_link_params->preemphasis);
		break;
	}

	switch (edp_link_params->vswing) {
	case EDP_VSWING_0_4V:
		dev_priv->vbt.edp_vswing = DP_TRAIN_VOLTAGE_SWING_LEVEL_0;
		break;
	case EDP_VSWING_0_6V:
		dev_priv->vbt.edp_vswing = DP_TRAIN_VOLTAGE_SWING_LEVEL_1;
		break;
	case EDP_VSWING_0_8V:
		dev_priv->vbt.edp_vswing = DP_TRAIN_VOLTAGE_SWING_LEVEL_2;
		break;
	case EDP_VSWING_1_2V:
		dev_priv->vbt.edp_vswing = DP_TRAIN_VOLTAGE_SWING_LEVEL_3;
		break;
	default:
		DRM_DEBUG_KMS("VBT has unknown eDP voltage swing value %u\n",
			      edp_link_params->vswing);
		break;
	}

	if (bdb->version >= 173) {
		uint8_t vswing;

		/* Don't read from VBT if module parameter has valid value*/
		if (i915.edp_vswing) {
			dev_priv->edp_low_vswing = i915.edp_vswing == 1;
		} else {
			vswing = (edp->edp_vswing_preemph >> (panel_type * 4)) & 0xF;
			dev_priv->edp_low_vswing = vswing == 0;
		}
	}
}

static void
parse_psr(struct drm_i915_private *dev_priv, const struct bdb_header *bdb)
{
	const struct bdb_psr *psr;
	const struct psr_table *psr_table;

	psr = find_section(bdb, BDB_PSR);
	if (!psr) {
		DRM_DEBUG_KMS("No PSR BDB found.\n");
		return;
	}

	psr_table = &psr->psr_table[panel_type];

	dev_priv->vbt.psr.full_link = psr_table->full_link;
	dev_priv->vbt.psr.require_aux_wakeup = psr_table->require_aux_to_wakeup;

	/* Allowed VBT values goes from 0 to 15 */
	dev_priv->vbt.psr.idle_frames = psr_table->idle_frames < 0 ? 0 :
		psr_table->idle_frames > 15 ? 15 : psr_table->idle_frames;

	switch (psr_table->lines_to_wait) {
	case 0:
		dev_priv->vbt.psr.lines_to_wait = PSR_0_LINES_TO_WAIT;
		break;
	case 1:
		dev_priv->vbt.psr.lines_to_wait = PSR_1_LINE_TO_WAIT;
		break;
	case 2:
		dev_priv->vbt.psr.lines_to_wait = PSR_4_LINES_TO_WAIT;
		break;
	case 3:
		dev_priv->vbt.psr.lines_to_wait = PSR_8_LINES_TO_WAIT;
		break;
	default:
		DRM_DEBUG_KMS("VBT has unknown PSR lines to wait %u\n",
			      psr_table->lines_to_wait);
		break;
	}

	dev_priv->vbt.psr.tp1_wakeup_time = psr_table->tp1_wakeup_time;
	dev_priv->vbt.psr.tp2_tp3_wakeup_time = psr_table->tp2_tp3_wakeup_time;
}

static void
parse_mipi_config(struct drm_i915_private *dev_priv,
		  const struct bdb_header *bdb)
{
	const struct bdb_mipi_config *start;
	const struct mipi_config *config;
	const struct mipi_pps_data *pps;

	/* parse MIPI blocks only if LFP type is MIPI */
	if (!dev_priv->vbt.has_mipi)
		return;

	/* Initialize this to undefined indicating no generic MIPI support */
	dev_priv->vbt.dsi.panel_id = MIPI_DSI_UNDEFINED_PANEL_ID;

	/* Block #40 is already parsed and panel_fixed_mode is
	 * stored in dev_priv->lfp_lvds_vbt_mode
	 * resuse this when needed
	 */

	/* Parse #52 for panel index used from panel_type already
	 * parsed
	 */
	start = find_section(bdb, BDB_MIPI_CONFIG);
	if (!start) {
		DRM_DEBUG_KMS("No MIPI config BDB found");
		return;
	}

	DRM_DEBUG_DRIVER("Found MIPI Config block, panel index = %d\n",
								panel_type);

	/*
	 * get hold of the correct configuration block and pps data as per
	 * the panel_type as index
	 */
	config = &start->config[panel_type];
	pps = &start->pps[panel_type];

	/* store as of now full data. Trim when we realise all is not needed */
	dev_priv->vbt.dsi.config = kmemdup(config, sizeof(struct mipi_config), GFP_KERNEL);
	if (!dev_priv->vbt.dsi.config)
		return;

	dev_priv->vbt.dsi.pps = kmemdup(pps, sizeof(struct mipi_pps_data), GFP_KERNEL);
	if (!dev_priv->vbt.dsi.pps) {
		kfree(dev_priv->vbt.dsi.config);
		return;
	}

	/* We have mandatory mipi config blocks. Initialize as generic panel */
	dev_priv->vbt.dsi.panel_id = MIPI_DSI_GENERIC_PANEL_ID;
}

/* Find the sequence block and size for the given panel. */
static const u8 *
find_panel_sequence_block(const struct bdb_mipi_sequence *sequence,
			  u16 panel_id, u32 *seq_size)
{
	u32 total = get_blocksize(sequence);
	const u8 *data = &sequence->data[0];
	u8 current_id;
	u32 current_size;
	int header_size = sequence->version >= 3 ? 5 : 3;
	int index = 0;
	int i;

	/* skip new block size */
	if (sequence->version >= 3)
		data += 4;

	for (i = 0; i < MAX_MIPI_CONFIGURATIONS && index < total; i++) {
		if (index + header_size > total) {
			DRM_ERROR("Invalid sequence block (header)\n");
			return NULL;
		}

		current_id = *(data + index);
		if (sequence->version >= 3)
			current_size = *((const u32 *)(data + index + 1));
		else
			current_size = *((const u16 *)(data + index + 1));

		index += header_size;

		if (index + current_size > total) {
			DRM_ERROR("Invalid sequence block\n");
			return NULL;
		}

		if (current_id == panel_id) {
			*seq_size = current_size;
			return data + index;
		}

		index += current_size;
	}

	DRM_ERROR("Sequence block detected but no valid configuration\n");

	return NULL;
}

static int goto_next_sequence(const u8 *data, int index, int total)
{
	u16 len;

	/* Skip Sequence Byte. */
	for (index = index + 1; index < total; index += len) {
		u8 operation_byte = *(data + index);
		index++;

		switch (operation_byte) {
		case MIPI_SEQ_ELEM_END:
			return index;
		case MIPI_SEQ_ELEM_SEND_PKT:
			if (index + 4 > total)
				return 0;

			len = *((const u16 *)(data + index + 2)) + 4;
			break;
		case MIPI_SEQ_ELEM_DELAY:
			len = 4;
			break;
		case MIPI_SEQ_ELEM_GPIO:
			len = 2;
			break;
		case MIPI_SEQ_ELEM_I2C:
			if (index + 7 > total)
				return 0;
			len = *(data + index + 6) + 7;
			break;
		default:
			DRM_ERROR("Unknown operation byte\n");
			return 0;
		}
	}

	return 0;
}

static int goto_next_sequence_v3(const u8 *data, int index, int total)
{
	int seq_end;
	u16 len;

	/*
	 * Could skip sequence based on Size of Sequence alone, but also do some
	 * checking on the structure.
	 */
	if (total < 5) {
		DRM_ERROR("Too small sequence size\n");
		return 0;
	}

	seq_end = index + *((const u32 *)(data + 1));
	if (seq_end > total) {
		DRM_ERROR("Invalid sequence size\n");
		return 0;
	}

	/* Skip Sequence Byte and Size of Sequence. */
	for (index = index + 5; index < total; index += len) {
		u8 operation_byte = *(data + index);
		index++;

		if (operation_byte == MIPI_SEQ_ELEM_END) {
			if (index != seq_end) {
				DRM_ERROR("Invalid element structure\n");
				return 0;
			}
			return index;
		}

		len = *(data + index);
		index++;

		/*
		 * FIXME: Would be nice to check elements like for v1/v2 in
		 * goto_next_sequence() above.
		 */
		switch (operation_byte) {
		case MIPI_SEQ_ELEM_SEND_PKT:
		case MIPI_SEQ_ELEM_DELAY:
		case MIPI_SEQ_ELEM_GPIO:
		case MIPI_SEQ_ELEM_I2C:
		case MIPI_SEQ_ELEM_SPI:
		case MIPI_SEQ_ELEM_PMIC:
			break;
		default:
			DRM_ERROR("Unknown operation byte %u\n",
				  operation_byte);
			break;
		}
	}

	return 0;
}

static void
parse_mipi_sequence(struct drm_i915_private *dev_priv,
		    const struct bdb_header *bdb)
{
	const struct bdb_mipi_sequence *sequence;
	const u8 *seq_data;
	u32 seq_size;
	u8 *data;
	int index = 0;

	/* Only our generic panel driver uses the sequence block. */
	if (dev_priv->vbt.dsi.panel_id != MIPI_DSI_GENERIC_PANEL_ID)
		return;

	sequence = find_section(bdb, BDB_MIPI_SEQUENCE);
	if (!sequence) {
		DRM_DEBUG_KMS("No MIPI Sequence found, parsing complete\n");
		return;
	}

	/* Fail gracefully for forward incompatible sequence block. */
	if (sequence->version >= 4) {
		DRM_ERROR("Unable to parse MIPI Sequence Block v%u\n",
			  sequence->version);
		return;
	}

	DRM_DEBUG_DRIVER("Found MIPI sequence block v%u\n", sequence->version);

	seq_data = find_panel_sequence_block(sequence, panel_type, &seq_size);
	if (!seq_data)
		return;

	data = kmemdup(seq_data, seq_size, GFP_KERNEL);
	if (!data)
		return;

	/* Parse the sequences, store pointers to each sequence. */
	for (;;) {
		u8 seq_id = *(data + index);
		if (seq_id == MIPI_SEQ_END)
			break;

		if (seq_id >= MIPI_SEQ_MAX) {
			DRM_ERROR("Unknown sequence %u\n", seq_id);
			goto err;
		}

		dev_priv->vbt.dsi.sequence[seq_id] = data + index;

		if (sequence->version >= 3)
			index = goto_next_sequence_v3(data, index, seq_size);
		else
			index = goto_next_sequence(data, index, seq_size);
		if (!index) {
			DRM_ERROR("Invalid sequence %u\n", seq_id);
			goto err;
		}
	}

	dev_priv->vbt.dsi.data = data;
	dev_priv->vbt.dsi.size = seq_size;
	dev_priv->vbt.dsi.seq_version = sequence->version;

	DRM_DEBUG_DRIVER("MIPI related VBT parsing complete\n");
	return;

err:
	kfree(data);
	memset(dev_priv->vbt.dsi.sequence, 0, sizeof(dev_priv->vbt.dsi.sequence));
}

static u8 translate_iboost(u8 val)
{
	static const u8 mapping[] = { 1, 3, 7 }; /* See VBT spec */

	if (val >= ARRAY_SIZE(mapping)) {
		DRM_DEBUG_KMS("Unsupported I_boost value found in VBT (%d), display may not work properly\n", val);
		return 0;
	}
	return mapping[val];
}

static void parse_ddi_port(struct drm_i915_private *dev_priv, enum port port,
			   const struct bdb_header *bdb)
{
	union child_device_config *it, *child = NULL;
	struct ddi_vbt_port_info *info = &dev_priv->vbt.ddi_port_info[port];
	uint8_t hdmi_level_shift;
	int i, j;
	bool is_dvi, is_hdmi, is_dp, is_edp, is_crt;
	uint8_t aux_channel, ddc_pin;
	/* Each DDI port can have more than one value on the "DVO Port" field,
	 * so look for all the possible values for each port and abort if more
	 * than one is found. */
	int dvo_ports[][3] = {
		{DVO_PORT_HDMIA, DVO_PORT_DPA, -1},
		{DVO_PORT_HDMIB, DVO_PORT_DPB, -1},
		{DVO_PORT_HDMIC, DVO_PORT_DPC, -1},
		{DVO_PORT_HDMID, DVO_PORT_DPD, -1},
		{DVO_PORT_CRT, DVO_PORT_HDMIE, DVO_PORT_DPE},
	};

	/* Find the child device to use, abort if more than one found. */
	for (i = 0; i < dev_priv->vbt.child_dev_num; i++) {
		it = dev_priv->vbt.child_dev + i;

		for (j = 0; j < 3; j++) {
			if (dvo_ports[port][j] == -1)
				break;

			if (it->common.dvo_port == dvo_ports[port][j]) {
				if (child) {
					DRM_DEBUG_KMS("More than one child device for port %c in VBT.\n",
						      port_name(port));
					return;
				}
				child = it;
			}
		}
	}
	if (!child)
		return;

	aux_channel = child->raw[25];
	ddc_pin = child->common.ddc_pin;

	is_dvi = child->common.device_type & DEVICE_TYPE_TMDS_DVI_SIGNALING;
	is_dp = child->common.device_type & DEVICE_TYPE_DISPLAYPORT_OUTPUT;
	is_crt = child->common.device_type & DEVICE_TYPE_ANALOG_OUTPUT;
	is_hdmi = is_dvi && (child->common.device_type & DEVICE_TYPE_NOT_HDMI_OUTPUT) == 0;
	is_edp = is_dp && (child->common.device_type & DEVICE_TYPE_INTERNAL_CONNECTOR);

	info->supports_dvi = is_dvi;
	info->supports_hdmi = is_hdmi;
	info->supports_dp = is_dp;

	DRM_DEBUG_KMS("Port %c VBT info: DP:%d HDMI:%d DVI:%d EDP:%d CRT:%d\n",
		      port_name(port), is_dp, is_hdmi, is_dvi, is_edp, is_crt);

	if (is_edp && is_dvi)
		DRM_DEBUG_KMS("Internal DP port %c is TMDS compatible\n",
			      port_name(port));
	if (is_crt && port != PORT_E)
		DRM_DEBUG_KMS("Port %c is analog\n", port_name(port));
	if (is_crt && (is_dvi || is_dp))
		DRM_DEBUG_KMS("Analog port %c is also DP or TMDS compatible\n",
			      port_name(port));
	if (is_dvi && (port == PORT_A || port == PORT_E))
		DRM_DEBUG_KMS("Port %c is TMDS compatible\n", port_name(port));
	if (!is_dvi && !is_dp && !is_crt)
		DRM_DEBUG_KMS("Port %c is not DP/TMDS/CRT compatible\n",
			      port_name(port));
	if (is_edp && (port == PORT_B || port == PORT_C || port == PORT_E))
		DRM_DEBUG_KMS("Port %c is internal DP\n", port_name(port));

	if (is_dvi) {
		if (port == PORT_E) {
			info->alternate_ddc_pin = ddc_pin;
			/* if DDIE share ddc pin with other port, then
			 * dvi/hdmi couldn't exist on the shared port.
			 * Otherwise they share the same ddc bin and system
			 * couldn't communicate with them seperately. */
			if (ddc_pin == DDC_PIN_B) {
				dev_priv->vbt.ddi_port_info[PORT_B].supports_dvi = 0;
				dev_priv->vbt.ddi_port_info[PORT_B].supports_hdmi = 0;
			} else if (ddc_pin == DDC_PIN_C) {
				dev_priv->vbt.ddi_port_info[PORT_C].supports_dvi = 0;
				dev_priv->vbt.ddi_port_info[PORT_C].supports_hdmi = 0;
			} else if (ddc_pin == DDC_PIN_D) {
				dev_priv->vbt.ddi_port_info[PORT_D].supports_dvi = 0;
				dev_priv->vbt.ddi_port_info[PORT_D].supports_hdmi = 0;
			}
		} else if (ddc_pin == DDC_PIN_B && port != PORT_B)
			DRM_DEBUG_KMS("Unexpected DDC pin for port B\n");
		else if (ddc_pin == DDC_PIN_C && port != PORT_C)
			DRM_DEBUG_KMS("Unexpected DDC pin for port C\n");
		else if (ddc_pin == DDC_PIN_D && port != PORT_D)
			DRM_DEBUG_KMS("Unexpected DDC pin for port D\n");
	}

	if (is_dp) {
		if (port == PORT_E) {
			info->alternate_aux_channel = aux_channel;
			/* if DDIE share aux channel with other port, then
			 * DP couldn't exist on the shared port. Otherwise
			 * they share the same aux channel and system
			 * couldn't communicate with them seperately. */
			if (aux_channel == DP_AUX_A)
				dev_priv->vbt.ddi_port_info[PORT_A].supports_dp = 0;
			else if (aux_channel == DP_AUX_B)
				dev_priv->vbt.ddi_port_info[PORT_B].supports_dp = 0;
			else if (aux_channel == DP_AUX_C)
				dev_priv->vbt.ddi_port_info[PORT_C].supports_dp = 0;
			else if (aux_channel == DP_AUX_D)
				dev_priv->vbt.ddi_port_info[PORT_D].supports_dp = 0;
		}
		else if (aux_channel == DP_AUX_A && port != PORT_A)
			DRM_DEBUG_KMS("Unexpected AUX channel for port A\n");
		else if (aux_channel == DP_AUX_B && port != PORT_B)
			DRM_DEBUG_KMS("Unexpected AUX channel for port B\n");
		else if (aux_channel == DP_AUX_C && port != PORT_C)
			DRM_DEBUG_KMS("Unexpected AUX channel for port C\n");
		else if (aux_channel == DP_AUX_D && port != PORT_D)
			DRM_DEBUG_KMS("Unexpected AUX channel for port D\n");
	}

	if (bdb->version >= 158) {
		/* The VBT HDMI level shift values match the table we have. */
		hdmi_level_shift = child->raw[7] & 0xF;
		DRM_DEBUG_KMS("VBT HDMI level shift for port %c: %d\n",
			      port_name(port),
			      hdmi_level_shift);
		info->hdmi_level_shift = hdmi_level_shift;
	}

	/* Parse the I_boost config for SKL and above */
	if (bdb->version >= 196 && (child->common.flags_1 & IBOOST_ENABLE)) {
		info->dp_boost_level = translate_iboost(child->common.iboost_level & 0xF);
		DRM_DEBUG_KMS("VBT (e)DP boost level for port %c: %d\n",
			      port_name(port), info->dp_boost_level);
		info->hdmi_boost_level = translate_iboost(child->common.iboost_level >> 4);
		DRM_DEBUG_KMS("VBT HDMI boost level for port %c: %d\n",
			      port_name(port), info->hdmi_boost_level);
	}
}

static void parse_ddi_ports(struct drm_i915_private *dev_priv,
			    const struct bdb_header *bdb)
{
	enum port port;

	if (!HAS_DDI(dev_priv))
		return;

	if (!dev_priv->vbt.child_dev_num)
		return;

	if (bdb->version < 155)
		return;

	for (port = PORT_A; port < I915_MAX_PORTS; port++)
		parse_ddi_port(dev_priv, port, bdb);
}

static void
parse_device_mapping(struct drm_i915_private *dev_priv,
		     const struct bdb_header *bdb)
{
	const struct bdb_general_definitions *p_defs;
	const union child_device_config *p_child;
	union child_device_config *child_dev_ptr;
	int i, child_device_num, count;
	u8 expected_size;
	u16 block_size;

	p_defs = find_section(bdb, BDB_GENERAL_DEFINITIONS);
	if (!p_defs) {
		DRM_DEBUG_KMS("No general definition block is found, no devices defined.\n");
		return;
	}
	if (bdb->version < 195) {
		expected_size = sizeof(struct old_child_dev_config);
	} else if (bdb->version == 195) {
		expected_size = 37;
	} else if (bdb->version <= 197) {
		expected_size = 38;
	} else {
		expected_size = 38;
		BUILD_BUG_ON(sizeof(*p_child) < 38);
		DRM_DEBUG_DRIVER("Expected child device config size for VBT version %u not known; assuming %u\n",
				 bdb->version, expected_size);
	}

	/* The legacy sized child device config is the minimum we need. */
	if (p_defs->child_dev_size < sizeof(struct old_child_dev_config)) {
		DRM_ERROR("Child device config size %u is too small.\n",
			  p_defs->child_dev_size);
		return;
	}

	/* Flag an error for unexpected size, but continue anyway. */
	if (p_defs->child_dev_size != expected_size)
		DRM_ERROR("Unexpected child device config size %u (expected %u for VBT version %u)\n",
			  p_defs->child_dev_size, expected_size, bdb->version);

	/* get the block size of general definitions */
	block_size = get_blocksize(p_defs);
	/* get the number of child device */
	child_device_num = (block_size - sizeof(*p_defs)) /
				p_defs->child_dev_size;
	count = 0;
	/* get the number of child device that is present */
	for (i = 0; i < child_device_num; i++) {
		p_child = child_device_ptr(p_defs, i);
		if (!p_child->common.device_type) {
			/* skip the device block if device type is invalid */
			continue;
		}
		count++;
	}
	if (!count) {
		DRM_DEBUG_KMS("no child dev is parsed from VBT\n");
		return;
	}
	dev_priv->vbt.child_dev = kcalloc(count, sizeof(*p_child), GFP_KERNEL);
	if (!dev_priv->vbt.child_dev) {
		DRM_DEBUG_KMS("No memory space for child device\n");
		return;
	}

	dev_priv->vbt.child_dev_num = count;
	count = 0;
	for (i = 0; i < child_device_num; i++) {
		p_child = child_device_ptr(p_defs, i);
		if (!p_child->common.device_type) {
			/* skip the device block if device type is invalid */
			continue;
		}

		if (p_child->common.dvo_port >= DVO_PORT_MIPIA
		    && p_child->common.dvo_port <= DVO_PORT_MIPID
		    &&p_child->common.device_type & DEVICE_TYPE_MIPI_OUTPUT) {
			DRM_DEBUG_KMS("Found MIPI as LFP\n");
			dev_priv->vbt.has_mipi = 1;
			dev_priv->vbt.dsi.port = p_child->common.dvo_port;
		}

		child_dev_ptr = dev_priv->vbt.child_dev + count;
		count++;

		/*
		 * Copy as much as we know (sizeof) and is available
		 * (child_dev_size) of the child device. Accessing the data must
		 * depend on VBT version.
		 */
		memcpy(child_dev_ptr, p_child,
		       min_t(size_t, p_defs->child_dev_size, sizeof(*p_child)));
	}
	return;
}

static void
init_vbt_defaults(struct drm_i915_private *dev_priv)
{
	enum port port;

	dev_priv->vbt.crt_ddc_pin = GMBUS_PIN_VGADDC;

	/* Default to having backlight */
	dev_priv->vbt.backlight.present = true;

	/* LFP panel data */
	dev_priv->vbt.lvds_dither = 1;
	dev_priv->vbt.lvds_vbt = 0;

	/* SDVO panel data */
	dev_priv->vbt.sdvo_lvds_vbt_mode = NULL;

	/* general features */
	dev_priv->vbt.int_tv_support = 1;
	dev_priv->vbt.int_crt_support = 1;

	/* Default to using SSC */
	dev_priv->vbt.lvds_use_ssc = 1;
	/*
	 * Core/SandyBridge/IvyBridge use alternative (120MHz) reference
	 * clock for LVDS.
	 */
	dev_priv->vbt.lvds_ssc_freq = intel_bios_ssc_frequency(dev_priv,
			!HAS_PCH_SPLIT(dev_priv));
	DRM_DEBUG_KMS("Set default to SSC at %d kHz\n", dev_priv->vbt.lvds_ssc_freq);

	for (port = PORT_A; port < I915_MAX_PORTS; port++) {
		struct ddi_vbt_port_info *info =
			&dev_priv->vbt.ddi_port_info[port];

		info->hdmi_level_shift = HDMI_LEVEL_SHIFT_UNKNOWN;

		info->supports_dvi = (port != PORT_A && port != PORT_E);
		info->supports_hdmi = info->supports_dvi;
		info->supports_dp = (port != PORT_E);
	}
}

static const struct bdb_header *get_bdb_header(const struct vbt_header *vbt)
{
	const void *_vbt = vbt;

	return _vbt + vbt->bdb_offset;
}

/**
 * intel_bios_is_valid_vbt - does the given buffer contain a valid VBT
 * @buf:	pointer to a buffer to validate
 * @size:	size of the buffer
 *
 * Returns true on valid VBT.
 */
bool intel_bios_is_valid_vbt(const void *buf, size_t size)
{
	const struct vbt_header *vbt = buf;
	const struct bdb_header *bdb;

	if (!vbt)
		return false;

	if (sizeof(struct vbt_header) > size) {
		DRM_DEBUG_DRIVER("VBT header incomplete\n");
		return false;
	}

	if (memcmp(vbt->signature, "$VBT", 4)) {
		DRM_DEBUG_DRIVER("VBT invalid signature\n");
		return false;
	}

	if (vbt->bdb_offset + sizeof(struct bdb_header) > size) {
		DRM_DEBUG_DRIVER("BDB header incomplete\n");
		return false;
	}

	bdb = get_bdb_header(vbt);
	if (vbt->bdb_offset + bdb->bdb_size > size) {
		DRM_DEBUG_DRIVER("BDB incomplete\n");
		return false;
	}

	return vbt;
}

static const struct vbt_header *find_vbt(void __iomem *bios, size_t size)
{
	size_t i;

	/* Scour memory looking for the VBT signature. */
	for (i = 0; i + 4 < size; i++) {
		void *vbt;

		if (ioread32(bios + i) != *((const u32 *) "$VBT"))
			continue;

		/*
		 * This is the one place where we explicitly discard the address
		 * space (__iomem) of the BIOS/VBT.
		 */
		vbt = (void __force *) bios + i;
		if (intel_bios_is_valid_vbt(vbt, size - i))
			return vbt;

		break;
	}

	return NULL;
}

/**
 * intel_bios_init - find VBT and initialize settings from the BIOS
 * @dev_priv: i915 device instance
 *
 * Loads the Video BIOS and checks that the VBT exists.  Sets scratch registers
 * to appropriate values.
 *
 * Returns 0 on success, nonzero on failure.
 */
int
intel_bios_init(struct drm_i915_private *dev_priv)
{
	struct pci_dev *pdev = dev_priv->dev->pdev;
	const struct vbt_header *vbt = dev_priv->opregion.vbt;
	const struct bdb_header *bdb;
	u8 __iomem *bios = NULL;

	if (HAS_PCH_NOP(dev_priv))
		return -ENODEV;

	init_vbt_defaults(dev_priv);

	if (!vbt) {
		size_t size;

		bios = pci_map_rom(pdev, &size);
		if (!bios)
			return -1;

		vbt = find_vbt(bios, size);
		if (!vbt) {
			pci_unmap_rom(pdev, bios);
			return -1;
		}

		DRM_DEBUG_KMS("Found valid VBT in PCI ROM\n");
	}

	bdb = get_bdb_header(vbt);

	DRM_DEBUG_KMS("VBT signature \"%.*s\", BDB version %d\n",
		      (int)sizeof(vbt->signature), vbt->signature, bdb->version);

	/* Grab useful general definitions */
	parse_general_features(dev_priv, bdb);
	parse_general_definitions(dev_priv, bdb);
	parse_lfp_panel_data(dev_priv, bdb);
	parse_lfp_backlight(dev_priv, bdb);
	parse_sdvo_panel_data(dev_priv, bdb);
	parse_sdvo_device_mapping(dev_priv, bdb);
	parse_device_mapping(dev_priv, bdb);
	parse_driver_features(dev_priv, bdb);
	parse_edp(dev_priv, bdb);
	parse_psr(dev_priv, bdb);
	parse_mipi_config(dev_priv, bdb);
	parse_mipi_sequence(dev_priv, bdb);
	parse_ddi_ports(dev_priv, bdb);

	if (bios)
		pci_unmap_rom(pdev, bios);

	return 0;
}