drivers/gpu/drm/drm_dp_dual_mode_helper.c - linux - Git at Google

 /*
  * Copyright © 2016 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 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 COPYRIGHT HOLDER(S) OR AUTHOR(S) 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.
  */

 #include <linux/errno.h>
 #include <linux/export.h>
 #include <linux/i2c.h>
 #include <linux/slab.h>
 #include <linux/string.h>
 #include <drm/drm_dp_dual_mode_helper.h>
 #include <drm/drmP.h>

 /**
  * DOC: dp dual mode helpers
  *
  * Helper functions to deal with DP dual mode (aka. DP++) adaptors.
  *
  * Type 1:
  * Adaptor registers (if any) and the sink DDC bus may be accessed via I2C.
  *
  * Type 2:
  * Adaptor registers and sink DDC bus can be accessed either via I2C or
  * I2C-over-AUX. Source devices may choose to implement either of these
  * access methods.
  */

 #define DP_DUAL_MODE_SLAVE_ADDRESS 0x40

 /**
  * drm_dp_dual_mode_read - Read from the DP dual mode adaptor register(s)
  * @adapter: I2C adapter for the DDC bus
  * @offset: register offset
  * @buffer: buffer for return data
  * @size: sizo of the buffer
  *
  * Reads @size bytes from the DP dual mode adaptor registers
  * starting at @offset.
  *
  * Returns:
  * 0 on success, negative error code on failure
  */
 ssize_t drm_dp_dual_mode_read(struct i2c_adapter *adapter,
 			      u8 offset, void *buffer, size_t size)
 {
 	struct i2c_msg msgs[] = {
 		{
 			.addr = DP_DUAL_MODE_SLAVE_ADDRESS,
 			.flags = 0,
 			.len = 1,
 			.buf = &offset,
 		},
 		{
 			.addr = DP_DUAL_MODE_SLAVE_ADDRESS,
 			.flags = I2C_M_RD,
 			.len = size,
 			.buf = buffer,
 		},
 	};
 	int ret;

 	ret = i2c_transfer(adapter, msgs, ARRAY_SIZE(msgs));
 	if (ret < 0)
 		return ret;
 	if (ret != ARRAY_SIZE(msgs))
 		return -EPROTO;

 	return 0;
 }
 EXPORT_SYMBOL(drm_dp_dual_mode_read);

 /**
  * drm_dp_dual_mode_write - Write to the DP dual mode adaptor register(s)
  * @adapter: I2C adapter for the DDC bus
  * @offset: register offset
  * @buffer: buffer for write data
  * @size: sizo of the buffer
  *
  * Writes @size bytes to the DP dual mode adaptor registers
  * starting at @offset.
  *
  * Returns:
  * 0 on success, negative error code on failure
  */
 ssize_t drm_dp_dual_mode_write(struct i2c_adapter *adapter,
 			       u8 offset, const void *buffer, size_t size)
 {
 	struct i2c_msg msg = {
 		.addr = DP_DUAL_MODE_SLAVE_ADDRESS,
 		.flags = 0,
 		.len = 1 + size,
 		.buf = NULL,
 	};
 	void *data;
 	int ret;

 	data = kmalloc(msg.len, GFP_TEMPORARY);
 	if (!data)
 		return -ENOMEM;

 	msg.buf = data;

 	memcpy(data, &offset, 1);
 	memcpy(data + 1, buffer, size);

 	ret = i2c_transfer(adapter, &msg, 1);

 	kfree(data);

 	if (ret < 0)
 		return ret;
 	if (ret != 1)
 		return -EPROTO;

 	return 0;
 }
 EXPORT_SYMBOL(drm_dp_dual_mode_write);

 static bool is_hdmi_adaptor(const char hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN])
 {
 	static const char dp_dual_mode_hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN] =
 		"DP-HDMI ADAPTOR\x04";

 	return memcmp(hdmi_id, dp_dual_mode_hdmi_id,
 		      sizeof(dp_dual_mode_hdmi_id)) == 0;
 }

 static bool is_type1_adaptor(uint8_t adaptor_id)
 {
 	return adaptor_id == 0 || adaptor_id == 0xff;
 }

 static bool is_type2_adaptor(uint8_t adaptor_id)
 {
 	return adaptor_id == (DP_DUAL_MODE_TYPE_TYPE2 |
 			      DP_DUAL_MODE_REV_TYPE2);
 }

 static bool is_lspcon_adaptor(const char hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN],
 			      const uint8_t adaptor_id)
 {
 	return is_hdmi_adaptor(hdmi_id) &&
 		(adaptor_id == (DP_DUAL_MODE_TYPE_TYPE2 |
 		 DP_DUAL_MODE_TYPE_HAS_DPCD));
 }

 /**
  * drm_dp_dual_mode_detect - Identify the DP dual mode adaptor
  * @adapter: I2C adapter for the DDC bus
  *
  * Attempt to identify the type of the DP dual mode adaptor used.
  *
  * Note that when the answer is @DRM_DP_DUAL_MODE_UNKNOWN it's not
  * certain whether we're dealing with a native HDMI port or
  * a type 1 DVI dual mode adaptor. The driver will have to use
  * some other hardware/driver specific mechanism to make that
  * distinction.
  *
  * Returns:
  * The type of the DP dual mode adaptor used
  */
 enum drm_dp_dual_mode_type drm_dp_dual_mode_detect(struct i2c_adapter *adapter)
 {
 	char hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN] = {};
 	uint8_t adaptor_id = 0x00;
 	ssize_t ret;

 	/*
 	 * Let's see if the adaptor is there the by reading the
 	 * HDMI ID registers.
 	 *
 	 * Note that type 1 DVI adaptors are not required to implemnt
 	 * any registers, and that presents a problem for detection.
 	 * If the i2c transfer is nacked, we may or may not be dealing
 	 * with a type 1 DVI adaptor. Some other mechanism of detecting
 	 * the presence of the adaptor is required. One way would be
 	 * to check the state of the CONFIG1 pin, Another method would
 	 * simply require the driver to know whether the port is a DP++
 	 * port or a native HDMI port. Both of these methods are entirely
 	 * hardware/driver specific so we can't deal with them here.
 	 */
 	ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_HDMI_ID,
 				    hdmi_id, sizeof(hdmi_id));
 	DRM_DEBUG_KMS("DP dual mode HDMI ID: %*pE (err %zd)\n",
 		      ret ? 0 : (int)sizeof(hdmi_id), hdmi_id, ret);
 	if (ret)
 		return DRM_DP_DUAL_MODE_UNKNOWN;

 	/*
 	 * Sigh. Some (maybe all?) type 1 adaptors are broken and ack
 	 * the offset but ignore it, and instead they just always return
 	 * data from the start of the HDMI ID buffer. So for a broken
 	 * type 1 HDMI adaptor a single byte read will always give us
 	 * 0x44, and for a type 1 DVI adaptor it should give 0x00
 	 * (assuming it implements any registers). Fortunately neither
 	 * of those values will match the type 2 signature of the
 	 * DP_DUAL_MODE_ADAPTOR_ID register so we can proceed with
 	 * the type 2 adaptor detection safely even in the presence
 	 * of broken type 1 adaptors.
 	 */
 	ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_ADAPTOR_ID,
 				    &adaptor_id, sizeof(adaptor_id));
 	DRM_DEBUG_KMS("DP dual mode adaptor ID: %02x (err %zd)\n",
 		      adaptor_id, ret);
 	if (ret == 0) {
 		if (is_lspcon_adaptor(hdmi_id, adaptor_id))
 			return DRM_DP_DUAL_MODE_LSPCON;
 		if (is_type2_adaptor(adaptor_id)) {
 			if (is_hdmi_adaptor(hdmi_id))
 				return DRM_DP_DUAL_MODE_TYPE2_HDMI;
 			else
 				return DRM_DP_DUAL_MODE_TYPE2_DVI;
 		}
 		/*
 		 * If neither a proper type 1 ID nor a broken type 1 adaptor
 		 * as described above, assume type 1, but let the user know
 		 * that we may have misdetected the type.
 		 */
 		if (!is_type1_adaptor(adaptor_id) && adaptor_id != hdmi_id[0])
 			DRM_ERROR("Unexpected DP dual mode adaptor ID %02x\n",
 				  adaptor_id);

 	}

 	if (is_hdmi_adaptor(hdmi_id))
 		return DRM_DP_DUAL_MODE_TYPE1_HDMI;
 	else
 		return DRM_DP_DUAL_MODE_TYPE1_DVI;
 }
 EXPORT_SYMBOL(drm_dp_dual_mode_detect);

 /**
  * drm_dp_dual_mode_max_tmds_clock - Max TMDS clock for DP dual mode adaptor
  * @type: DP dual mode adaptor type
  * @adapter: I2C adapter for the DDC bus
  *
  * Determine the max TMDS clock the adaptor supports based on the
  * type of the dual mode adaptor and the DP_DUAL_MODE_MAX_TMDS_CLOCK
  * register (on type2 adaptors). As some type 1 adaptors have
  * problems with registers (see comments in drm_dp_dual_mode_detect())
  * we don't read the register on those, instead we simply assume
  * a 165 MHz limit based on the specification.
  *
  * Returns:
  * Maximum supported TMDS clock rate for the DP dual mode adaptor in kHz.
  */
 int drm_dp_dual_mode_max_tmds_clock(enum drm_dp_dual_mode_type type,
 				    struct i2c_adapter *adapter)
 {
 	uint8_t max_tmds_clock;
 	ssize_t ret;

 	/* native HDMI so no limit */
 	if (type == DRM_DP_DUAL_MODE_NONE)
 		return 0;

 	/*
 	 * Type 1 adaptors are limited to 165MHz
 	 * Type 2 adaptors can tells us their limit
 	 */
 	if (type < DRM_DP_DUAL_MODE_TYPE2_DVI)
 		return 165000;

 	ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_MAX_TMDS_CLOCK,
 				    &max_tmds_clock, sizeof(max_tmds_clock));
 	if (ret || max_tmds_clock == 0x00 || max_tmds_clock == 0xff) {
 		DRM_DEBUG_KMS("Failed to query max TMDS clock\n");
 		return 165000;
 	}

 	return max_tmds_clock * 5000 / 2;
 }
 EXPORT_SYMBOL(drm_dp_dual_mode_max_tmds_clock);

 /**
  * drm_dp_dual_mode_get_tmds_output - Get the state of the TMDS output buffers in the DP dual mode adaptor
  * @type: DP dual mode adaptor type
  * @adapter: I2C adapter for the DDC bus
  * @enabled: current state of the TMDS output buffers
  *
  * Get the state of the TMDS output buffers in the adaptor. For
  * type2 adaptors this is queried from the DP_DUAL_MODE_TMDS_OEN
  * register. As some type 1 adaptors have problems with registers
  * (see comments in drm_dp_dual_mode_detect()) we don't read the
  * register on those, instead we simply assume that the buffers
  * are always enabled.
  *
  * Returns:
  * 0 on success, negative error code on failure
  */
 int drm_dp_dual_mode_get_tmds_output(enum drm_dp_dual_mode_type type,
 				     struct i2c_adapter *adapter,
 				     bool *enabled)
 {
 	uint8_t tmds_oen;
 	ssize_t ret;

 	if (type < DRM_DP_DUAL_MODE_TYPE2_DVI) {
 		*enabled = true;
 		return 0;
 	}

 	ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_TMDS_OEN,
 				    &tmds_oen, sizeof(tmds_oen));
 	if (ret) {
 		DRM_DEBUG_KMS("Failed to query state of TMDS output buffers\n");
 		return ret;
 	}

 	*enabled = !(tmds_oen & DP_DUAL_MODE_TMDS_DISABLE);

 	return 0;
 }
 EXPORT_SYMBOL(drm_dp_dual_mode_get_tmds_output);

 /**
  * drm_dp_dual_mode_set_tmds_output - Enable/disable TMDS output buffers in the DP dual mode adaptor
  * @type: DP dual mode adaptor type
  * @adapter: I2C adapter for the DDC bus
  * @enable: enable (as opposed to disable) the TMDS output buffers
  *
  * Set the state of the TMDS output buffers in the adaptor. For
  * type2 this is set via the DP_DUAL_MODE_TMDS_OEN register. As
  * some type 1 adaptors have problems with registers (see comments
  * in drm_dp_dual_mode_detect()) we avoid touching the register,
  * making this function a no-op on type 1 adaptors.
  *
  * Returns:
  * 0 on success, negative error code on failure
  */
 int drm_dp_dual_mode_set_tmds_output(enum drm_dp_dual_mode_type type,
 				     struct i2c_adapter *adapter, bool enable)
 {
 	uint8_t tmds_oen = enable ? 0 : DP_DUAL_MODE_TMDS_DISABLE;
 	ssize_t ret;

 	if (type < DRM_DP_DUAL_MODE_TYPE2_DVI)
 		return 0;

 	ret = drm_dp_dual_mode_write(adapter, DP_DUAL_MODE_TMDS_OEN,
 				     &tmds_oen, sizeof(tmds_oen));
 	if (ret) {
 		DRM_DEBUG_KMS("Failed to %s TMDS output buffers\n",
 			      enable ? "enable" : "disable");
 		return ret;
 	}

 	return 0;
 }
 EXPORT_SYMBOL(drm_dp_dual_mode_set_tmds_output);

 /**
  * drm_dp_get_dual_mode_type_name - Get the name of the DP dual mode adaptor type as a string
  * @type: DP dual mode adaptor type
  *
  * Returns:
  * String representation of the DP dual mode adaptor type
  */
 const char *drm_dp_get_dual_mode_type_name(enum drm_dp_dual_mode_type type)
 {
 	switch (type) {
 	case DRM_DP_DUAL_MODE_NONE:
 		return "none";
 	case DRM_DP_DUAL_MODE_TYPE1_DVI:
 		return "type 1 DVI";
 	case DRM_DP_DUAL_MODE_TYPE1_HDMI:
 		return "type 1 HDMI";
 	case DRM_DP_DUAL_MODE_TYPE2_DVI:
 		return "type 2 DVI";
 	case DRM_DP_DUAL_MODE_TYPE2_HDMI:
 		return "type 2 HDMI";
 	default:
 		WARN_ON(type != DRM_DP_DUAL_MODE_UNKNOWN);
 		return "unknown";
 	}
 }
 EXPORT_SYMBOL(drm_dp_get_dual_mode_type_name);

 /**
  * drm_lspcon_get_mode: Get LSPCON's current mode of operation by
  * reading offset (0x80, 0x41)
  * @adapter: I2C-over-aux adapter
  * @mode: current lspcon mode of operation output variable
  *
  * Returns:
  * 0 on success, sets the current_mode value to appropriate mode
  * -error on failure
  */
 int drm_lspcon_get_mode(struct i2c_adapter *adapter,
 			enum drm_lspcon_mode *mode)
 {
 	u8 data;
 	int ret = 0;

 	if (!mode) {
 		DRM_ERROR("NULL input\n");
 		return -EINVAL;
 	}

 	/* Read Status: i2c over aux */
 	ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_LSPCON_CURRENT_MODE,
 				    &data, sizeof(data));
 	if (ret < 0) {
 		DRM_ERROR("LSPCON read(0x80, 0x41) failed\n");
 		return -EFAULT;
 	}

 	if (data & DP_DUAL_MODE_LSPCON_MODE_PCON)
 		*mode = DRM_LSPCON_MODE_PCON;
 	else
 		*mode = DRM_LSPCON_MODE_LS;
 	return 0;
 }
 EXPORT_SYMBOL(drm_lspcon_get_mode);

 /**
  * drm_lspcon_set_mode: Change LSPCON's mode of operation by
  * writing offset (0x80, 0x40)
  * @adapter: I2C-over-aux adapter
  * @mode: required mode of operation
  *
  * Returns:
  * 0 on success, -error on failure/timeout
  */
 int drm_lspcon_set_mode(struct i2c_adapter *adapter,
 			enum drm_lspcon_mode mode)
 {
 	u8 data = 0;
 	int ret;
 	int time_out = 200;
 	enum drm_lspcon_mode current_mode;

 	if (mode == DRM_LSPCON_MODE_PCON)
 		data = DP_DUAL_MODE_LSPCON_MODE_PCON;

 	/* Change mode */
 	ret = drm_dp_dual_mode_write(adapter, DP_DUAL_MODE_LSPCON_MODE_CHANGE,
 				     &data, sizeof(data));
 	if (ret < 0) {
 		DRM_ERROR("LSPCON mode change failed\n");
 		return ret;
 	}

 	/*
 	 * Confirm mode change by reading the status bit.
 	 * Sometimes, it takes a while to change the mode,
 	 * so wait and retry until time out or done.
 	 */
 	do {
 		ret = drm_lspcon_get_mode(adapter, &current_mode);
 		if (ret) {
 			DRM_ERROR("can't confirm LSPCON mode change\n");
 			return ret;
 		} else {
 			if (current_mode != mode) {
 				msleep(10);
 				time_out -= 10;
 			} else {
 				DRM_DEBUG_KMS("LSPCON mode changed to %s\n",
 						mode == DRM_LSPCON_MODE_LS ?
 						"LS" : "PCON");
 				return 0;
 			}
 		}
 	} while (time_out);

 	DRM_ERROR("LSPCON mode change timed out\n");
 	return -ETIMEDOUT;
 }
 EXPORT_SYMBOL(drm_lspcon_set_mode);
	/*
	* Copyright © 2016 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 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 COPYRIGHT HOLDER(S) OR AUTHOR(S) 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.
	*/

	#include <linux/errno.h>
	#include <linux/export.h>
	#include <linux/i2c.h>
	#include <linux/slab.h>
	#include <linux/string.h>
	#include <drm/drm_dp_dual_mode_helper.h>
	#include <drm/drmP.h>

	/**
	* DOC: dp dual mode helpers
	*
	* Helper functions to deal with DP dual mode (aka. DP++) adaptors.
	*
	* Type 1:
	* Adaptor registers (if any) and the sink DDC bus may be accessed via I2C.
	*
	* Type 2:
	* Adaptor registers and sink DDC bus can be accessed either via I2C or
	* I2C-over-AUX. Source devices may choose to implement either of these
	* access methods.
	*/

	#define DP_DUAL_MODE_SLAVE_ADDRESS 0x40

	/**
	* drm_dp_dual_mode_read - Read from the DP dual mode adaptor register(s)
	* @adapter: I2C adapter for the DDC bus
	* @offset: register offset
	* @buffer: buffer for return data
	* @size: sizo of the buffer
	*
	* Reads @size bytes from the DP dual mode adaptor registers
	* starting at @offset.
	*
	* Returns:
	* 0 on success, negative error code on failure
	*/
	ssize_t drm_dp_dual_mode_read(struct i2c_adapter *adapter,
	u8 offset, void *buffer, size_t size)
	{
	struct i2c_msg msgs[] = {
	{
	.addr = DP_DUAL_MODE_SLAVE_ADDRESS,
	.flags = 0,
	.len = 1,
	.buf = &offset,
	},
	{
	.addr = DP_DUAL_MODE_SLAVE_ADDRESS,
	.flags = I2C_M_RD,
	.len = size,
	.buf = buffer,
	},
	};
	int ret;

	ret = i2c_transfer(adapter, msgs, ARRAY_SIZE(msgs));
	if (ret < 0)
	return ret;
	if (ret != ARRAY_SIZE(msgs))
	return -EPROTO;

	return 0;
	}
	EXPORT_SYMBOL(drm_dp_dual_mode_read);

	/**
	* drm_dp_dual_mode_write - Write to the DP dual mode adaptor register(s)
	* @adapter: I2C adapter for the DDC bus
	* @offset: register offset
	* @buffer: buffer for write data
	* @size: sizo of the buffer
	*
	* Writes @size bytes to the DP dual mode adaptor registers
	* starting at @offset.
	*
	* Returns:
	* 0 on success, negative error code on failure
	*/
	ssize_t drm_dp_dual_mode_write(struct i2c_adapter *adapter,
	u8 offset, const void *buffer, size_t size)
	{
	struct i2c_msg msg = {
	.addr = DP_DUAL_MODE_SLAVE_ADDRESS,
	.flags = 0,
	.len = 1 + size,
	.buf = NULL,
	};
	void *data;
	int ret;

	data = kmalloc(msg.len, GFP_TEMPORARY);
	if (!data)
	return -ENOMEM;

	msg.buf = data;

	memcpy(data, &offset, 1);
	memcpy(data + 1, buffer, size);

	ret = i2c_transfer(adapter, &msg, 1);

	kfree(data);

	if (ret < 0)
	return ret;
	if (ret != 1)
	return -EPROTO;

	return 0;
	}
	EXPORT_SYMBOL(drm_dp_dual_mode_write);

	static bool is_hdmi_adaptor(const char hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN])
	{
	static const char dp_dual_mode_hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN] =
	"DP-HDMI ADAPTOR\x04";

	return memcmp(hdmi_id, dp_dual_mode_hdmi_id,
	sizeof(dp_dual_mode_hdmi_id)) == 0;
	}

	static bool is_type1_adaptor(uint8_t adaptor_id)
	{
	return adaptor_id == 0 \|\| adaptor_id == 0xff;
	}

	static bool is_type2_adaptor(uint8_t adaptor_id)
	{
	return adaptor_id == (DP_DUAL_MODE_TYPE_TYPE2 \|
	DP_DUAL_MODE_REV_TYPE2);
	}

	static bool is_lspcon_adaptor(const char hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN],
	const uint8_t adaptor_id)
	{
	return is_hdmi_adaptor(hdmi_id) &&
	(adaptor_id == (DP_DUAL_MODE_TYPE_TYPE2 \|
	DP_DUAL_MODE_TYPE_HAS_DPCD));
	}

	/**
	* drm_dp_dual_mode_detect - Identify the DP dual mode adaptor
	* @adapter: I2C adapter for the DDC bus
	*
	* Attempt to identify the type of the DP dual mode adaptor used.
	*
	* Note that when the answer is @DRM_DP_DUAL_MODE_UNKNOWN it's not
	* certain whether we're dealing with a native HDMI port or
	* a type 1 DVI dual mode adaptor. The driver will have to use
	* some other hardware/driver specific mechanism to make that
	* distinction.
	*
	* Returns:
	* The type of the DP dual mode adaptor used
	*/
	enum drm_dp_dual_mode_type drm_dp_dual_mode_detect(struct i2c_adapter *adapter)
	{
	char hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN] = {};
	uint8_t adaptor_id = 0x00;
	ssize_t ret;

	/*
	* Let's see if the adaptor is there the by reading the
	* HDMI ID registers.
	*
	* Note that type 1 DVI adaptors are not required to implemnt
	* any registers, and that presents a problem for detection.
	* If the i2c transfer is nacked, we may or may not be dealing
	* with a type 1 DVI adaptor. Some other mechanism of detecting
	* the presence of the adaptor is required. One way would be
	* to check the state of the CONFIG1 pin, Another method would
	* simply require the driver to know whether the port is a DP++
	* port or a native HDMI port. Both of these methods are entirely
	* hardware/driver specific so we can't deal with them here.
	*/
	ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_HDMI_ID,
	hdmi_id, sizeof(hdmi_id));
	DRM_DEBUG_KMS("DP dual mode HDMI ID: %*pE (err %zd)\n",
	ret ? 0 : (int)sizeof(hdmi_id), hdmi_id, ret);
	if (ret)
	return DRM_DP_DUAL_MODE_UNKNOWN;

	/*
	* Sigh. Some (maybe all?) type 1 adaptors are broken and ack
	* the offset but ignore it, and instead they just always return
	* data from the start of the HDMI ID buffer. So for a broken
	* type 1 HDMI adaptor a single byte read will always give us
	* 0x44, and for a type 1 DVI adaptor it should give 0x00
	* (assuming it implements any registers). Fortunately neither
	* of those values will match the type 2 signature of the
	* DP_DUAL_MODE_ADAPTOR_ID register so we can proceed with
	* the type 2 adaptor detection safely even in the presence
	* of broken type 1 adaptors.
	*/
	ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_ADAPTOR_ID,
	&adaptor_id, sizeof(adaptor_id));
	DRM_DEBUG_KMS("DP dual mode adaptor ID: %02x (err %zd)\n",
	adaptor_id, ret);
	if (ret == 0) {
	if (is_lspcon_adaptor(hdmi_id, adaptor_id))
	return DRM_DP_DUAL_MODE_LSPCON;
	if (is_type2_adaptor(adaptor_id)) {
	if (is_hdmi_adaptor(hdmi_id))
	return DRM_DP_DUAL_MODE_TYPE2_HDMI;
	else
	return DRM_DP_DUAL_MODE_TYPE2_DVI;
	}
	/*
	* If neither a proper type 1 ID nor a broken type 1 adaptor
	* as described above, assume type 1, but let the user know
	* that we may have misdetected the type.
	*/
	if (!is_type1_adaptor(adaptor_id) && adaptor_id != hdmi_id[0])
	DRM_ERROR("Unexpected DP dual mode adaptor ID %02x\n",
	adaptor_id);

	}

	if (is_hdmi_adaptor(hdmi_id))
	return DRM_DP_DUAL_MODE_TYPE1_HDMI;
	else
	return DRM_DP_DUAL_MODE_TYPE1_DVI;
	}
	EXPORT_SYMBOL(drm_dp_dual_mode_detect);

	/**
	* drm_dp_dual_mode_max_tmds_clock - Max TMDS clock for DP dual mode adaptor
	* @type: DP dual mode adaptor type
	* @adapter: I2C adapter for the DDC bus
	*
	* Determine the max TMDS clock the adaptor supports based on the
	* type of the dual mode adaptor and the DP_DUAL_MODE_MAX_TMDS_CLOCK
	* register (on type2 adaptors). As some type 1 adaptors have
	* problems with registers (see comments in drm_dp_dual_mode_detect())
	* we don't read the register on those, instead we simply assume
	* a 165 MHz limit based on the specification.
	*
	* Returns:
	* Maximum supported TMDS clock rate for the DP dual mode adaptor in kHz.
	*/
	int drm_dp_dual_mode_max_tmds_clock(enum drm_dp_dual_mode_type type,
	struct i2c_adapter *adapter)
	{
	uint8_t max_tmds_clock;
	ssize_t ret;

	/* native HDMI so no limit */
	if (type == DRM_DP_DUAL_MODE_NONE)
	return 0;

	/*
	* Type 1 adaptors are limited to 165MHz
	* Type 2 adaptors can tells us their limit
	*/
	if (type < DRM_DP_DUAL_MODE_TYPE2_DVI)
	return 165000;

	ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_MAX_TMDS_CLOCK,
	&max_tmds_clock, sizeof(max_tmds_clock));
	if (ret \|\| max_tmds_clock == 0x00 \|\| max_tmds_clock == 0xff) {
	DRM_DEBUG_KMS("Failed to query max TMDS clock\n");
	return 165000;
	}

	return max_tmds_clock * 5000 / 2;
	}
	EXPORT_SYMBOL(drm_dp_dual_mode_max_tmds_clock);

	/**
	* drm_dp_dual_mode_get_tmds_output - Get the state of the TMDS output buffers in the DP dual mode adaptor
	* @type: DP dual mode adaptor type
	* @adapter: I2C adapter for the DDC bus
	* @enabled: current state of the TMDS output buffers
	*
	* Get the state of the TMDS output buffers in the adaptor. For
	* type2 adaptors this is queried from the DP_DUAL_MODE_TMDS_OEN
	* register. As some type 1 adaptors have problems with registers
	* (see comments in drm_dp_dual_mode_detect()) we don't read the
	* register on those, instead we simply assume that the buffers
	* are always enabled.
	*
	* Returns:
	* 0 on success, negative error code on failure
	*/
	int drm_dp_dual_mode_get_tmds_output(enum drm_dp_dual_mode_type type,
	struct i2c_adapter *adapter,
	bool *enabled)
	{
	uint8_t tmds_oen;
	ssize_t ret;

	if (type < DRM_DP_DUAL_MODE_TYPE2_DVI) {
	*enabled = true;
	return 0;
	}

	ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_TMDS_OEN,
	&tmds_oen, sizeof(tmds_oen));
	if (ret) {
	DRM_DEBUG_KMS("Failed to query state of TMDS output buffers\n");
	return ret;
	}

	*enabled = !(tmds_oen & DP_DUAL_MODE_TMDS_DISABLE);

	return 0;
	}
	EXPORT_SYMBOL(drm_dp_dual_mode_get_tmds_output);

	/**
	* drm_dp_dual_mode_set_tmds_output - Enable/disable TMDS output buffers in the DP dual mode adaptor
	* @type: DP dual mode adaptor type
	* @adapter: I2C adapter for the DDC bus
	* @enable: enable (as opposed to disable) the TMDS output buffers
	*
	* Set the state of the TMDS output buffers in the adaptor. For
	* type2 this is set via the DP_DUAL_MODE_TMDS_OEN register. As
	* some type 1 adaptors have problems with registers (see comments
	* in drm_dp_dual_mode_detect()) we avoid touching the register,
	* making this function a no-op on type 1 adaptors.
	*
	* Returns:
	* 0 on success, negative error code on failure
	*/
	int drm_dp_dual_mode_set_tmds_output(enum drm_dp_dual_mode_type type,
	struct i2c_adapter *adapter, bool enable)
	{
	uint8_t tmds_oen = enable ? 0 : DP_DUAL_MODE_TMDS_DISABLE;
	ssize_t ret;

	if (type < DRM_DP_DUAL_MODE_TYPE2_DVI)
	return 0;

	ret = drm_dp_dual_mode_write(adapter, DP_DUAL_MODE_TMDS_OEN,
	&tmds_oen, sizeof(tmds_oen));
	if (ret) {
	DRM_DEBUG_KMS("Failed to %s TMDS output buffers\n",
	enable ? "enable" : "disable");
	return ret;
	}

	return 0;
	}
	EXPORT_SYMBOL(drm_dp_dual_mode_set_tmds_output);

	/**
	* drm_dp_get_dual_mode_type_name - Get the name of the DP dual mode adaptor type as a string
	* @type: DP dual mode adaptor type
	*
	* Returns:
	* String representation of the DP dual mode adaptor type
	*/
	const char *drm_dp_get_dual_mode_type_name(enum drm_dp_dual_mode_type type)
	{
	switch (type) {
	case DRM_DP_DUAL_MODE_NONE:
	return "none";
	case DRM_DP_DUAL_MODE_TYPE1_DVI:
	return "type 1 DVI";
	case DRM_DP_DUAL_MODE_TYPE1_HDMI:
	return "type 1 HDMI";
	case DRM_DP_DUAL_MODE_TYPE2_DVI:
	return "type 2 DVI";
	case DRM_DP_DUAL_MODE_TYPE2_HDMI:
	return "type 2 HDMI";
	default:
	WARN_ON(type != DRM_DP_DUAL_MODE_UNKNOWN);
	return "unknown";
	}
	}
	EXPORT_SYMBOL(drm_dp_get_dual_mode_type_name);

	/**
	* drm_lspcon_get_mode: Get LSPCON's current mode of operation by
	* reading offset (0x80, 0x41)
	* @adapter: I2C-over-aux adapter
	* @mode: current lspcon mode of operation output variable
	*
	* Returns:
	* 0 on success, sets the current_mode value to appropriate mode
	* -error on failure
	*/
	int drm_lspcon_get_mode(struct i2c_adapter *adapter,
	enum drm_lspcon_mode *mode)
	{
	u8 data;
	int ret = 0;

	if (!mode) {
	DRM_ERROR("NULL input\n");
	return -EINVAL;
	}

	/* Read Status: i2c over aux */
	ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_LSPCON_CURRENT_MODE,
	&data, sizeof(data));
	if (ret < 0) {
	DRM_ERROR("LSPCON read(0x80, 0x41) failed\n");
	return -EFAULT;
	}

	if (data & DP_DUAL_MODE_LSPCON_MODE_PCON)
	*mode = DRM_LSPCON_MODE_PCON;
	else
	*mode = DRM_LSPCON_MODE_LS;
	return 0;
	}
	EXPORT_SYMBOL(drm_lspcon_get_mode);

	/**
	* drm_lspcon_set_mode: Change LSPCON's mode of operation by
	* writing offset (0x80, 0x40)
	* @adapter: I2C-over-aux adapter
	* @mode: required mode of operation
	*
	* Returns:
	* 0 on success, -error on failure/timeout
	*/
	int drm_lspcon_set_mode(struct i2c_adapter *adapter,
	enum drm_lspcon_mode mode)
	{
	u8 data = 0;
	int ret;
	int time_out = 200;
	enum drm_lspcon_mode current_mode;

	if (mode == DRM_LSPCON_MODE_PCON)
	data = DP_DUAL_MODE_LSPCON_MODE_PCON;

	/* Change mode */
	ret = drm_dp_dual_mode_write(adapter, DP_DUAL_MODE_LSPCON_MODE_CHANGE,
	&data, sizeof(data));
	if (ret < 0) {
	DRM_ERROR("LSPCON mode change failed\n");
	return ret;
	}

	/*
	* Confirm mode change by reading the status bit.
	* Sometimes, it takes a while to change the mode,
	* so wait and retry until time out or done.
	*/
	do {
	ret = drm_lspcon_get_mode(adapter, &current_mode);
	if (ret) {
	DRM_ERROR("can't confirm LSPCON mode change\n");
	return ret;
	} else {
	if (current_mode != mode) {
	msleep(10);
	time_out -= 10;
	} else {
	DRM_DEBUG_KMS("LSPCON mode changed to %s\n",
	mode == DRM_LSPCON_MODE_LS ?
	"LS" : "PCON");
	return 0;
	}
	}
	} while (time_out);

	DRM_ERROR("LSPCON mode change timed out\n");
	return -ETIMEDOUT;
	}
	EXPORT_SYMBOL(drm_lspcon_set_mode);