linux/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 "drmP.h"
#include "drm.h"
#include "i915_drm.h"
#include "i915_drv.h"
#include "intel_bios.h"

#define	SLAVE_ADDR1	0x70
#define	SLAVE_ADDR2	0x72

static int panel_type;

static void *
find_section(struct bdb_header *bdb, int section_id)
{
	u8 *base = (u8 *)bdb;
	int index = 0;
	u16 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 < total) {
		current_id = *(base + index);
		index++;
		current_size = *((u16 *)(base + index));
		index += 2;
		if (current_id == section_id)
			return base + index;
		index += current_size;
	}

	return NULL;
}

static u16
get_blocksize(void *p)
{
	u16 *block_ptr, block_size;

	block_ptr = (u16 *)((char *)p - 2);
	block_size = *block_ptr;
	return block_size;
}

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 bool
lvds_dvo_timing_equal_size(const struct lvds_dvo_timing *a,
			   const struct lvds_dvo_timing *b)
{
	if (a->hactive_hi != b->hactive_hi ||
	    a->hactive_lo != b->hactive_lo)
		return false;

	if (a->hsync_off_hi != b->hsync_off_hi ||
	    a->hsync_off_lo != b->hsync_off_lo)
		return false;

	if (a->hsync_pulse_width != b->hsync_pulse_width)
		return false;

	if (a->hblank_hi != b->hblank_hi ||
	    a->hblank_lo != b->hblank_lo)
		return false;

	if (a->vactive_hi != b->vactive_hi ||
	    a->vactive_lo != b->vactive_lo)
		return false;

	if (a->vsync_off != b->vsync_off)
		return false;

	if (a->vsync_pulse_width != b->vsync_pulse_width)
		return false;

	if (a->vblank_hi != b->vblank_hi ||
	    a->vblank_lo != b->vblank_lo)
		return false;

	return true;
}

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);
}

/* Try to find integrated panel data */
static void
parse_lfp_panel_data(struct drm_i915_private *dev_priv,
			    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;
	struct drm_display_mode *panel_fixed_mode;
	int i, downclock;

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

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

	panel_type = lvds_options->panel_type;

	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->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->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);

	/*
	 * Iterate over the LVDS panel timing info to find the lowest clock
	 * for the native resolution.
	 */
	downclock = panel_dvo_timing->clock;
	for (i = 0; i < 16; i++) {
		const struct lvds_dvo_timing *dvo_timing;

		dvo_timing = get_lvds_dvo_timing(lvds_lfp_data,
						 lvds_lfp_data_ptrs,
						 i);
		if (lvds_dvo_timing_equal_size(dvo_timing, panel_dvo_timing) &&
		    dvo_timing->clock < downclock)
			downclock = dvo_timing->clock;
	}

	if (downclock < panel_dvo_timing->clock && i915_lvds_downclock) {
		dev_priv->lvds_downclock_avail = 1;
		dev_priv->lvds_downclock = downclock * 10;
		DRM_DEBUG_KMS("LVDS downclock is found in VBT. "
			      "Normal Clock %dKHz, downclock %dKHz\n",
			      panel_fixed_mode->clock, 10*downclock);
	}
}

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

	index = i915_vbt_sdvo_panel_type;
	if (index == -1) {
		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->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_device *dev,
				    bool alternate)
{
	switch (INTEL_INFO(dev)->gen) {
	case 2:
		return alternate ? 66 : 48;
	case 3:
	case 4:
		return alternate ? 100 : 96;
	default:
		return alternate ? 100 : 120;
	}
}

static void
parse_general_features(struct drm_i915_private *dev_priv,
		       struct bdb_header *bdb)
{
	struct drm_device *dev = dev_priv->dev;
	struct bdb_general_features *general;

	general = find_section(bdb, BDB_GENERAL_FEATURES);
	if (general) {
		dev_priv->int_tv_support = general->int_tv_support;
		dev_priv->int_crt_support = general->int_crt_support;
		dev_priv->lvds_use_ssc = general->enable_ssc;
		dev_priv->lvds_ssc_freq =
			intel_bios_ssc_frequency(dev, general->ssc_freq);
		dev_priv->display_clock_mode = general->display_clock_mode;
		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\n",
			      dev_priv->int_tv_support,
			      dev_priv->int_crt_support,
			      dev_priv->lvds_use_ssc,
			      dev_priv->lvds_ssc_freq,
			      dev_priv->display_clock_mode);
	}
}

static void
parse_general_definitions(struct drm_i915_private *dev_priv,
			  struct bdb_header *bdb)
{
	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 (bus_pin >= 1 && bus_pin <= 6)
				dev_priv->crt_ddc_pin = bus_pin;
		} else {
			DRM_DEBUG_KMS("BDB_GD too small (%d). Invalid.\n",
				  block_size);
		}
	}
}

static void
parse_sdvo_device_mapping(struct drm_i915_private *dev_priv,
			  struct bdb_header *bdb)
{
	struct sdvo_device_mapping *p_mapping;
	struct bdb_general_definitions *p_defs;
	struct child_device_config *p_child;
	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;
	}
	/* judge whether the size of child device meets the requirements.
	 * If the child device size obtained from general definition block
	 * is different with sizeof(struct child_device_config), skip the
	 * parsing of sdvo device info
	 */
	if (p_defs->child_dev_size != sizeof(*p_child)) {
		/* different child dev size . Ignore it */
		DRM_DEBUG_KMS("different child size is found. Invalid.\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)) /
				sizeof(*p_child);
	count = 0;
	for (i = 0; i < child_device_num; i++) {
		p_child = &(p_defs->devices[i]);
		if (!p_child->device_type) {
			/* skip the device block if device type is invalid */
			continue;
		}
		if (p_child->slave_addr != SLAVE_ADDR1 &&
			p_child->slave_addr != SLAVE_ADDR2) {
			/*
			 * If the slave address is neither 0x70 nor 0x72,
			 * it is not a SDVO device. Skip it.
			 */
			continue;
		}
		if (p_child->dvo_port != DEVICE_PORT_DVOB &&
			p_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",
				p_child->slave_addr,
				(p_child->dvo_port == DEVICE_PORT_DVOB) ?
					"SDVOB" : "SDVOC");
		p_mapping = &(dev_priv->sdvo_mappings[p_child->dvo_port - 1]);
		if (!p_mapping->initialized) {
			p_mapping->dvo_port = p_child->dvo_port;
			p_mapping->slave_addr = p_child->slave_addr;
			p_mapping->dvo_wiring = p_child->dvo_wiring;
			p_mapping->ddc_pin = p_child->ddc_pin;
			p_mapping->i2c_pin = p_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 (p_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,
		       struct bdb_header *bdb)
{
	struct drm_device *dev = dev_priv->dev;
	struct bdb_driver_features *driver;

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

	if (SUPPORTS_EDP(dev) &&
	    driver->lvds_config == BDB_DRIVER_FEATURE_EDP)
		dev_priv->edp.support = 1;

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

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

	edp = find_section(bdb, BDB_EDP);
	if (!edp) {
		if (SUPPORTS_EDP(dev_priv->dev) && dev_priv->edp.support) {
			DRM_DEBUG_KMS("No eDP BDB found but eDP panel "
				      "supported, assume %dbpp panel color "
				      "depth.\n",
				      dev_priv->edp.bpp);
		}
		return;
	}

	switch ((edp->color_depth >> (panel_type * 2)) & 3) {
	case EDP_18BPP:
		dev_priv->edp.bpp = 18;
		break;
	case EDP_24BPP:
		dev_priv->edp.bpp = 24;
		break;
	case EDP_30BPP:
		dev_priv->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->edp.pps = *edp_pps;

	dev_priv->edp.rate = edp_link_params->rate ? DP_LINK_BW_2_7 :
		DP_LINK_BW_1_62;
	switch (edp_link_params->lanes) {
	case 0:
		dev_priv->edp.lanes = 1;
		break;
	case 1:
		dev_priv->edp.lanes = 2;
		break;
	case 3:
	default:
		dev_priv->edp.lanes = 4;
		break;
	}
	switch (edp_link_params->preemphasis) {
	case 0:
		dev_priv->edp.preemphasis = DP_TRAIN_PRE_EMPHASIS_0;
		break;
	case 1:
		dev_priv->edp.preemphasis = DP_TRAIN_PRE_EMPHASIS_3_5;
		break;
	case 2:
		dev_priv->edp.preemphasis = DP_TRAIN_PRE_EMPHASIS_6;
		break;
	case 3:
		dev_priv->edp.preemphasis = DP_TRAIN_PRE_EMPHASIS_9_5;
		break;
	}
	switch (edp_link_params->vswing) {
	case 0:
		dev_priv->edp.vswing = DP_TRAIN_VOLTAGE_SWING_400;
		break;
	case 1:
		dev_priv->edp.vswing = DP_TRAIN_VOLTAGE_SWING_600;
		break;
	case 2:
		dev_priv->edp.vswing = DP_TRAIN_VOLTAGE_SWING_800;
		break;
	case 3:
		dev_priv->edp.vswing = DP_TRAIN_VOLTAGE_SWING_1200;
		break;
	}
}

static void
parse_device_mapping(struct drm_i915_private *dev_priv,
		       struct bdb_header *bdb)
{
	struct bdb_general_definitions *p_defs;
	struct child_device_config *p_child, *child_dev_ptr;
	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, no devices defined.\n");
		return;
	}
	/* judge whether the size of child device meets the requirements.
	 * If the child device size obtained from general definition block
	 * is different with sizeof(struct child_device_config), skip the
	 * parsing of sdvo device info
	 */
	if (p_defs->child_dev_size != sizeof(*p_child)) {
		/* different child dev size . Ignore it */
		DRM_DEBUG_KMS("different child size is found. Invalid.\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)) /
				sizeof(*p_child);
	count = 0;
	/* get the number of child device that is present */
	for (i = 0; i < child_device_num; i++) {
		p_child = &(p_defs->devices[i]);
		if (!p_child->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->child_dev = kcalloc(count, sizeof(*p_child), GFP_KERNEL);
	if (!dev_priv->child_dev) {
		DRM_DEBUG_KMS("No memory space for child device\n");
		return;
	}

	dev_priv->child_dev_num = count;
	count = 0;
	for (i = 0; i < child_device_num; i++) {
		p_child = &(p_defs->devices[i]);
		if (!p_child->device_type) {
			/* skip the device block if device type is invalid */
			continue;
		}
		child_dev_ptr = dev_priv->child_dev + count;
		count++;
		memcpy((void *)child_dev_ptr, (void *)p_child,
					sizeof(*p_child));
	}
	return;
}

static void
init_vbt_defaults(struct drm_i915_private *dev_priv)
{
	struct drm_device *dev = dev_priv->dev;

	dev_priv->crt_ddc_pin = GMBUS_PORT_VGADDC;

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

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

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

	/* Default to using SSC */
	dev_priv->lvds_use_ssc = 1;
	dev_priv->lvds_ssc_freq = intel_bios_ssc_frequency(dev, 1);
	DRM_DEBUG_KMS("Set default to SSC at %dMHz\n", dev_priv->lvds_ssc_freq);

	/* eDP data */
	dev_priv->edp.bpp = 18;
}

/**
 * intel_parse_bios - find VBT and initialize settings from the BIOS
 * @dev: DRM device
 *
 * Loads the Video BIOS and checks that the VBT exists.  Sets scratch registers
 * to appropriate values.
 *
 * Returns 0 on success, nonzero on failure.
 */
bool
intel_parse_bios(struct drm_device *dev)
{
	struct drm_i915_private *dev_priv = dev->dev_private;
	struct pci_dev *pdev = dev->pdev;
	struct bdb_header *bdb = NULL;
	u8 __iomem *bios = NULL;

	init_vbt_defaults(dev_priv);

	/* XXX Should this validation be moved to intel_opregion.c? */
	if (dev_priv->opregion.vbt) {
		struct vbt_header *vbt = dev_priv->opregion.vbt;
		if (memcmp(vbt->signature, "$VBT", 4) == 0) {
			DRM_DEBUG_KMS("Using VBT from OpRegion: %20s\n",
					 vbt->signature);
			bdb = (struct bdb_header *)((char *)vbt + vbt->bdb_offset);
		} else
			dev_priv->opregion.vbt = NULL;
	}

	if (bdb == NULL) {
		struct vbt_header *vbt = NULL;
		size_t size;
		int i;

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

		/* Scour memory looking for the VBT signature */
		for (i = 0; i + 4 < size; i++) {
			if (!memcmp(bios + i, "$VBT", 4)) {
				vbt = (struct vbt_header *)(bios + i);
				break;
			}
		}

		if (!vbt) {
			DRM_ERROR("VBT signature missing\n");
			pci_unmap_rom(pdev, bios);
			return -1;
		}

		bdb = (struct bdb_header *)(bios + i + vbt->bdb_offset);
	}

	/* Grab useful general definitions */
	parse_general_features(dev_priv, bdb);
	parse_general_definitions(dev_priv, bdb);
	parse_lfp_panel_data(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);

	if (bios)
		pci_unmap_rom(pdev, bios);

	return 0;
}

/* Ensure that vital registers have been initialised, even if the BIOS
 * is absent or just failing to do its job.
 */
void intel_setup_bios(struct drm_device *dev)
{
	struct drm_i915_private *dev_priv = dev->dev_private;

	 /* Set the Panel Power On/Off timings if uninitialized. */
	if ((I915_READ(PP_ON_DELAYS) == 0) && (I915_READ(PP_OFF_DELAYS) == 0)) {
		/* Set T2 to 40ms and T5 to 200ms */
		I915_WRITE(PP_ON_DELAYS, 0x019007d0);

		/* Set T3 to 35ms and Tx to 200ms */
		I915_WRITE(PP_OFF_DELAYS, 0x015e07d0);
	}
}