drivers/gpu/drm/tegra/dpaux.c - kernel/msm-4.9 - Gitiles

 /*
  * Copyright (C) 2013 NVIDIA Corporation
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  */

 #include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/gpio.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/of_gpio.h>
 #include <linux/platform_device.h>
 #include <linux/reset.h>
 #include <linux/regulator/consumer.h>
 #include <linux/workqueue.h>

 #include <drm/drm_dp_helper.h>
 #include <drm/drm_panel.h>

 #include "dpaux.h"
 #include "drm.h"

 static DEFINE_MUTEX(dpaux_lock);
 static LIST_HEAD(dpaux_list);

 struct tegra_dpaux {
 	struct drm_dp_aux aux;
 	struct device *dev;

 	void __iomem *regs;
 	int irq;

 	struct tegra_output *output;

 	struct reset_control *rst;
 	struct clk *clk_parent;
 	struct clk *clk;

 	struct regulator *vdd;

 	struct completion complete;
 	struct work_struct work;
 	struct list_head list;
 };

 static inline struct tegra_dpaux *to_dpaux(struct drm_dp_aux *aux)
 {
 	return container_of(aux, struct tegra_dpaux, aux);
 }

 static inline struct tegra_dpaux *work_to_dpaux(struct work_struct *work)
 {
 	return container_of(work, struct tegra_dpaux, work);
 }

 static inline unsigned long tegra_dpaux_readl(struct tegra_dpaux *dpaux,
 					      unsigned long offset)
 {
 	return readl(dpaux->regs + (offset << 2));
 }

 static inline void tegra_dpaux_writel(struct tegra_dpaux *dpaux,
 				      unsigned long value,
 				      unsigned long offset)
 {
 	writel(value, dpaux->regs + (offset << 2));
 }

 static void tegra_dpaux_write_fifo(struct tegra_dpaux *dpaux, const u8 *buffer,
 				   size_t size)
 {
 	unsigned long offset = DPAUX_DP_AUXDATA_WRITE(0);
 	size_t i, j;

 	for (i = 0; i < size; i += 4) {
 		size_t num = min_t(size_t, size - i, 4);
 		unsigned long value = 0;

 		for (j = 0; j < num; j++)
 			value |= buffer[i + j] << (j * 8);

 		tegra_dpaux_writel(dpaux, value, offset++);
 	}
 }

 static void tegra_dpaux_read_fifo(struct tegra_dpaux *dpaux, u8 *buffer,
 				  size_t size)
 {
 	unsigned long offset = DPAUX_DP_AUXDATA_READ(0);
 	size_t i, j;

 	for (i = 0; i < size; i += 4) {
 		size_t num = min_t(size_t, size - i, 4);
 		unsigned long value;

 		value = tegra_dpaux_readl(dpaux, offset++);

 		for (j = 0; j < num; j++)
 			buffer[i + j] = value >> (j * 8);
 	}
 }

 static ssize_t tegra_dpaux_transfer(struct drm_dp_aux *aux,
 				    struct drm_dp_aux_msg *msg)
 {
 	unsigned long timeout = msecs_to_jiffies(250);
 	struct tegra_dpaux *dpaux = to_dpaux(aux);
 	unsigned long status;
 	ssize_t ret = 0;
 	u32 value;

 	/* Tegra has 4x4 byte DP AUX transmit and receive FIFOs. */
 	if (msg->size > 16)
 		return -EINVAL;

 	/*
 	 * Allow zero-sized messages only for I2C, in which case they specify
 	 * address-only transactions.
 	 */
 	if (msg->size < 1) {
 		switch (msg->request & ~DP_AUX_I2C_MOT) {
 		case DP_AUX_I2C_WRITE:
 		case DP_AUX_I2C_READ:
 			value = DPAUX_DP_AUXCTL_CMD_ADDRESS_ONLY;
 			break;

 		default:
 			return -EINVAL;
 		}
 	} else {
 		/* For non-zero-sized messages, set the CMDLEN field. */
 		value = DPAUX_DP_AUXCTL_CMDLEN(msg->size - 1);
 	}

 	switch (msg->request & ~DP_AUX_I2C_MOT) {
 	case DP_AUX_I2C_WRITE:
 		if (msg->request & DP_AUX_I2C_MOT)
 			value |= DPAUX_DP_AUXCTL_CMD_MOT_WR;
 		else
 			value |= DPAUX_DP_AUXCTL_CMD_I2C_WR;

 		break;

 	case DP_AUX_I2C_READ:
 		if (msg->request & DP_AUX_I2C_MOT)
 			value |= DPAUX_DP_AUXCTL_CMD_MOT_RD;
 		else
 			value |= DPAUX_DP_AUXCTL_CMD_I2C_RD;

 		break;

 	case DP_AUX_I2C_STATUS:
 		if (msg->request & DP_AUX_I2C_MOT)
 			value |= DPAUX_DP_AUXCTL_CMD_MOT_RQ;
 		else
 			value |= DPAUX_DP_AUXCTL_CMD_I2C_RQ;

 		break;

 	case DP_AUX_NATIVE_WRITE:
 		value |= DPAUX_DP_AUXCTL_CMD_AUX_WR;
 		break;

 	case DP_AUX_NATIVE_READ:
 		value |= DPAUX_DP_AUXCTL_CMD_AUX_RD;
 		break;

 	default:
 		return -EINVAL;
 	}

 	tegra_dpaux_writel(dpaux, msg->address, DPAUX_DP_AUXADDR);
 	tegra_dpaux_writel(dpaux, value, DPAUX_DP_AUXCTL);

 	if ((msg->request & DP_AUX_I2C_READ) == 0) {
 		tegra_dpaux_write_fifo(dpaux, msg->buffer, msg->size);
 		ret = msg->size;
 	}

 	/* start transaction */
 	value = tegra_dpaux_readl(dpaux, DPAUX_DP_AUXCTL);
 	value |= DPAUX_DP_AUXCTL_TRANSACTREQ;
 	tegra_dpaux_writel(dpaux, value, DPAUX_DP_AUXCTL);

 	status = wait_for_completion_timeout(&dpaux->complete, timeout);
 	if (!status)
 		return -ETIMEDOUT;

 	/* read status and clear errors */
 	value = tegra_dpaux_readl(dpaux, DPAUX_DP_AUXSTAT);
 	tegra_dpaux_writel(dpaux, 0xf00, DPAUX_DP_AUXSTAT);

 	if (value & DPAUX_DP_AUXSTAT_TIMEOUT_ERROR)
 		return -ETIMEDOUT;

 	if ((value & DPAUX_DP_AUXSTAT_RX_ERROR) ||
 	    (value & DPAUX_DP_AUXSTAT_SINKSTAT_ERROR) ||
 	    (value & DPAUX_DP_AUXSTAT_NO_STOP_ERROR))
 		return -EIO;

 	switch ((value & DPAUX_DP_AUXSTAT_REPLY_TYPE_MASK) >> 16) {
 	case 0x00:
 		msg->reply = DP_AUX_NATIVE_REPLY_ACK;
 		break;

 	case 0x01:
 		msg->reply = DP_AUX_NATIVE_REPLY_NACK;
 		break;

 	case 0x02:
 		msg->reply = DP_AUX_NATIVE_REPLY_DEFER;
 		break;

 	case 0x04:
 		msg->reply = DP_AUX_I2C_REPLY_NACK;
 		break;

 	case 0x08:
 		msg->reply = DP_AUX_I2C_REPLY_DEFER;
 		break;
 	}

 	if ((msg->size > 0) && (msg->reply == DP_AUX_NATIVE_REPLY_ACK)) {
 		if (msg->request & DP_AUX_I2C_READ) {
 			size_t count = value & DPAUX_DP_AUXSTAT_REPLY_MASK;

 			if (WARN_ON(count != msg->size))
 				count = min_t(size_t, count, msg->size);

 			tegra_dpaux_read_fifo(dpaux, msg->buffer, count);
 			ret = count;
 		}
 	}

 	return ret;
 }

 static void tegra_dpaux_hotplug(struct work_struct *work)
 {
 	struct tegra_dpaux *dpaux = work_to_dpaux(work);

 	if (dpaux->output)
 		drm_helper_hpd_irq_event(dpaux->output->connector.dev);
 }

 static irqreturn_t tegra_dpaux_irq(int irq, void *data)
 {
 	struct tegra_dpaux *dpaux = data;
 	irqreturn_t ret = IRQ_HANDLED;
 	unsigned long value;

 	/* clear interrupts */
 	value = tegra_dpaux_readl(dpaux, DPAUX_INTR_AUX);
 	tegra_dpaux_writel(dpaux, value, DPAUX_INTR_AUX);

 	if (value & (DPAUX_INTR_PLUG_EVENT | DPAUX_INTR_UNPLUG_EVENT))
 		schedule_work(&dpaux->work);

 	if (value & DPAUX_INTR_IRQ_EVENT) {
 		/* TODO: handle this */
 	}

 	if (value & DPAUX_INTR_AUX_DONE)
 		complete(&dpaux->complete);

 	return ret;
 }

 static int tegra_dpaux_probe(struct platform_device *pdev)
 {
 	struct tegra_dpaux *dpaux;
 	struct resource *regs;
 	unsigned long value;
 	int err;

 	dpaux = devm_kzalloc(&pdev->dev, sizeof(*dpaux), GFP_KERNEL);
 	if (!dpaux)
 		return -ENOMEM;

 	INIT_WORK(&dpaux->work, tegra_dpaux_hotplug);
 	init_completion(&dpaux->complete);
 	INIT_LIST_HEAD(&dpaux->list);
 	dpaux->dev = &pdev->dev;

 	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	dpaux->regs = devm_ioremap_resource(&pdev->dev, regs);
 	if (IS_ERR(dpaux->regs))
 		return PTR_ERR(dpaux->regs);

 	dpaux->irq = platform_get_irq(pdev, 0);
 	if (dpaux->irq < 0) {
 		dev_err(&pdev->dev, "failed to get IRQ\n");
 		return -ENXIO;
 	}

 	dpaux->rst = devm_reset_control_get(&pdev->dev, "dpaux");
 	if (IS_ERR(dpaux->rst))
 		return PTR_ERR(dpaux->rst);

 	dpaux->clk = devm_clk_get(&pdev->dev, NULL);
 	if (IS_ERR(dpaux->clk))
 		return PTR_ERR(dpaux->clk);

 	err = clk_prepare_enable(dpaux->clk);
 	if (err < 0)
 		return err;

 	reset_control_deassert(dpaux->rst);

 	dpaux->clk_parent = devm_clk_get(&pdev->dev, "parent");
 	if (IS_ERR(dpaux->clk_parent))
 		return PTR_ERR(dpaux->clk_parent);

 	err = clk_prepare_enable(dpaux->clk_parent);
 	if (err < 0)
 		return err;

 	err = clk_set_rate(dpaux->clk_parent, 270000000);
 	if (err < 0) {
 		dev_err(&pdev->dev, "failed to set clock to 270 MHz: %d\n",
 			err);
 		return err;
 	}

 	dpaux->vdd = devm_regulator_get(&pdev->dev, "vdd");
 	if (IS_ERR(dpaux->vdd))
 		return PTR_ERR(dpaux->vdd);

 	err = devm_request_irq(dpaux->dev, dpaux->irq, tegra_dpaux_irq, 0,
 			       dev_name(dpaux->dev), dpaux);
 	if (err < 0) {
 		dev_err(dpaux->dev, "failed to request IRQ#%u: %d\n",
 			dpaux->irq, err);
 		return err;
 	}

 	dpaux->aux.transfer = tegra_dpaux_transfer;
 	dpaux->aux.dev = &pdev->dev;

 	err = drm_dp_aux_register(&dpaux->aux);
 	if (err < 0)
 		return err;

 	/* enable and clear all interrupts */
 	value = DPAUX_INTR_AUX_DONE | DPAUX_INTR_IRQ_EVENT |
 		DPAUX_INTR_UNPLUG_EVENT | DPAUX_INTR_PLUG_EVENT;
 	tegra_dpaux_writel(dpaux, value, DPAUX_INTR_EN_AUX);
 	tegra_dpaux_writel(dpaux, value, DPAUX_INTR_AUX);

 	mutex_lock(&dpaux_lock);
 	list_add_tail(&dpaux->list, &dpaux_list);
 	mutex_unlock(&dpaux_lock);

 	platform_set_drvdata(pdev, dpaux);

 	return 0;
 }

 static int tegra_dpaux_remove(struct platform_device *pdev)
 {
 	struct tegra_dpaux *dpaux = platform_get_drvdata(pdev);

 	drm_dp_aux_unregister(&dpaux->aux);

 	mutex_lock(&dpaux_lock);
 	list_del(&dpaux->list);
 	mutex_unlock(&dpaux_lock);

 	cancel_work_sync(&dpaux->work);

 	clk_disable_unprepare(dpaux->clk_parent);
 	reset_control_assert(dpaux->rst);
 	clk_disable_unprepare(dpaux->clk);

 	return 0;
 }

 static const struct of_device_id tegra_dpaux_of_match[] = {
 	{ .compatible = "nvidia,tegra124-dpaux", },
 	{ },
 };
 MODULE_DEVICE_TABLE(of, tegra_dpaux_of_match);

 struct platform_driver tegra_dpaux_driver = {
 	.driver = {
 		.name = "tegra-dpaux",
 		.of_match_table = tegra_dpaux_of_match,
 	},
 	.probe = tegra_dpaux_probe,
 	.remove = tegra_dpaux_remove,
 };

 struct tegra_dpaux *tegra_dpaux_find_by_of_node(struct device_node *np)
 {
 	struct tegra_dpaux *dpaux;

 	mutex_lock(&dpaux_lock);

 	list_for_each_entry(dpaux, &dpaux_list, list)
 		if (np == dpaux->dev->of_node) {
 			mutex_unlock(&dpaux_lock);
 			return dpaux;
 		}

 	mutex_unlock(&dpaux_lock);

 	return NULL;
 }

 int tegra_dpaux_attach(struct tegra_dpaux *dpaux, struct tegra_output *output)
 {
 	unsigned long timeout;
 	int err;

 	output->connector.polled = DRM_CONNECTOR_POLL_HPD;
 	dpaux->output = output;

 	err = regulator_enable(dpaux->vdd);
 	if (err < 0)
 		return err;

 	timeout = jiffies + msecs_to_jiffies(250);

 	while (time_before(jiffies, timeout)) {
 		enum drm_connector_status status;

 		status = tegra_dpaux_detect(dpaux);
 		if (status == connector_status_connected)
 			return 0;

 		usleep_range(1000, 2000);
 	}

 	return -ETIMEDOUT;
 }

 int tegra_dpaux_detach(struct tegra_dpaux *dpaux)
 {
 	unsigned long timeout;
 	int err;

 	err = regulator_disable(dpaux->vdd);
 	if (err < 0)
 		return err;

 	timeout = jiffies + msecs_to_jiffies(250);

 	while (time_before(jiffies, timeout)) {
 		enum drm_connector_status status;

 		status = tegra_dpaux_detect(dpaux);
 		if (status == connector_status_disconnected) {
 			dpaux->output = NULL;
 			return 0;
 		}

 		usleep_range(1000, 2000);
 	}

 	return -ETIMEDOUT;
 }

 enum drm_connector_status tegra_dpaux_detect(struct tegra_dpaux *dpaux)
 {
 	unsigned long value;

 	value = tegra_dpaux_readl(dpaux, DPAUX_DP_AUXSTAT);

 	if (value & DPAUX_DP_AUXSTAT_HPD_STATUS)
 		return connector_status_connected;

 	return connector_status_disconnected;
 }

 int tegra_dpaux_enable(struct tegra_dpaux *dpaux)
 {
 	unsigned long value;

 	value = DPAUX_HYBRID_PADCTL_AUX_CMH(2) |
 		DPAUX_HYBRID_PADCTL_AUX_DRVZ(4) |
 		DPAUX_HYBRID_PADCTL_AUX_DRVI(0x18) |
 		DPAUX_HYBRID_PADCTL_AUX_INPUT_RCV |
 		DPAUX_HYBRID_PADCTL_MODE_AUX;
 	tegra_dpaux_writel(dpaux, value, DPAUX_HYBRID_PADCTL);

 	value = tegra_dpaux_readl(dpaux, DPAUX_HYBRID_SPARE);
 	value &= ~DPAUX_HYBRID_SPARE_PAD_POWER_DOWN;
 	tegra_dpaux_writel(dpaux, value, DPAUX_HYBRID_SPARE);

 	return 0;
 }

 int tegra_dpaux_disable(struct tegra_dpaux *dpaux)
 {
 	unsigned long value;

 	value = tegra_dpaux_readl(dpaux, DPAUX_HYBRID_SPARE);
 	value |= DPAUX_HYBRID_SPARE_PAD_POWER_DOWN;
 	tegra_dpaux_writel(dpaux, value, DPAUX_HYBRID_SPARE);

 	return 0;
 }

 int tegra_dpaux_prepare(struct tegra_dpaux *dpaux, u8 encoding)
 {
 	int err;

 	err = drm_dp_dpcd_writeb(&dpaux->aux, DP_MAIN_LINK_CHANNEL_CODING_SET,
 				 encoding);
 	if (err < 0)
 		return err;

 	return 0;
 }

 int tegra_dpaux_train(struct tegra_dpaux *dpaux, struct drm_dp_link *link,
 		      u8 pattern)
 {
 	u8 tp = pattern & DP_TRAINING_PATTERN_MASK;
 	u8 status[DP_LINK_STATUS_SIZE], values[4];
 	unsigned int i;
 	int err;

 	err = drm_dp_dpcd_writeb(&dpaux->aux, DP_TRAINING_PATTERN_SET, pattern);
 	if (err < 0)
 		return err;

 	if (tp == DP_TRAINING_PATTERN_DISABLE)
 		return 0;

 	for (i = 0; i < link->num_lanes; i++)
 		values[i] = DP_TRAIN_MAX_PRE_EMPHASIS_REACHED |
 			    DP_TRAIN_PRE_EMPH_LEVEL_0 |
 			    DP_TRAIN_MAX_SWING_REACHED |
 			    DP_TRAIN_VOLTAGE_SWING_LEVEL_0;

 	err = drm_dp_dpcd_write(&dpaux->aux, DP_TRAINING_LANE0_SET, values,
 				link->num_lanes);
 	if (err < 0)
 		return err;

 	usleep_range(500, 1000);

 	err = drm_dp_dpcd_read_link_status(&dpaux->aux, status);
 	if (err < 0)
 		return err;

 	switch (tp) {
 	case DP_TRAINING_PATTERN_1:
 		if (!drm_dp_clock_recovery_ok(status, link->num_lanes))
 			return -EAGAIN;

 		break;

 	case DP_TRAINING_PATTERN_2:
 		if (!drm_dp_channel_eq_ok(status, link->num_lanes))
 			return -EAGAIN;

 		break;

 	default:
 		dev_err(dpaux->dev, "unsupported training pattern %u\n", tp);
 		return -EINVAL;
 	}

 	err = drm_dp_dpcd_writeb(&dpaux->aux, DP_EDP_CONFIGURATION_SET, 0);
 	if (err < 0)
 		return err;

 	return 0;
 }
	/*
	* Copyright (C) 2013 NVIDIA Corporation
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 as
	* published by the Free Software Foundation.
	*/

	#include <linux/clk.h>
	#include <linux/delay.h>
	#include <linux/gpio.h>
	#include <linux/interrupt.h>
	#include <linux/io.h>
	#include <linux/of_gpio.h>
	#include <linux/platform_device.h>
	#include <linux/reset.h>
	#include <linux/regulator/consumer.h>
	#include <linux/workqueue.h>

	#include <drm/drm_dp_helper.h>
	#include <drm/drm_panel.h>

	#include "dpaux.h"
	#include "drm.h"

	static DEFINE_MUTEX(dpaux_lock);
	static LIST_HEAD(dpaux_list);

	struct tegra_dpaux {
	struct drm_dp_aux aux;
	struct device *dev;

	void __iomem *regs;
	int irq;

	struct tegra_output *output;

	struct reset_control *rst;
	struct clk *clk_parent;
	struct clk *clk;

	struct regulator *vdd;

	struct completion complete;
	struct work_struct work;
	struct list_head list;
	};

	static inline struct tegra_dpaux to_dpaux(struct drm_dp_aux aux)
	{
	return container_of(aux, struct tegra_dpaux, aux);
	}

	static inline struct tegra_dpaux work_to_dpaux(struct work_struct work)
	{
	return container_of(work, struct tegra_dpaux, work);
	}

	static inline unsigned long tegra_dpaux_readl(struct tegra_dpaux *dpaux,
	unsigned long offset)
	{
	return readl(dpaux->regs + (offset << 2));
	}

	static inline void tegra_dpaux_writel(struct tegra_dpaux *dpaux,
	unsigned long value,
	unsigned long offset)
	{
	writel(value, dpaux->regs + (offset << 2));
	}

	static void tegra_dpaux_write_fifo(struct tegra_dpaux dpaux, const u8 buffer,
	size_t size)
	{
	unsigned long offset = DPAUX_DP_AUXDATA_WRITE(0);
	size_t i, j;

	for (i = 0; i < size; i += 4) {
	size_t num = min_t(size_t, size - i, 4);
	unsigned long value = 0;

	for (j = 0; j < num; j++)
	value \|= buffer[i + j] << (j * 8);

	tegra_dpaux_writel(dpaux, value, offset++);
	}
	}

	static void tegra_dpaux_read_fifo(struct tegra_dpaux dpaux, u8 buffer,
	size_t size)
	{
	unsigned long offset = DPAUX_DP_AUXDATA_READ(0);
	size_t i, j;

	for (i = 0; i < size; i += 4) {
	size_t num = min_t(size_t, size - i, 4);
	unsigned long value;

	value = tegra_dpaux_readl(dpaux, offset++);

	for (j = 0; j < num; j++)
	buffer[i + j] = value >> (j * 8);
	}
	}

	static ssize_t tegra_dpaux_transfer(struct drm_dp_aux *aux,
	struct drm_dp_aux_msg *msg)
	{
	unsigned long timeout = msecs_to_jiffies(250);
	struct tegra_dpaux *dpaux = to_dpaux(aux);
	unsigned long status;
	ssize_t ret = 0;
	u32 value;

	/* Tegra has 4x4 byte DP AUX transmit and receive FIFOs. */
	if (msg->size > 16)
	return -EINVAL;

	/*
	* Allow zero-sized messages only for I2C, in which case they specify
	* address-only transactions.
	*/
	if (msg->size < 1) {
	switch (msg->request & ~DP_AUX_I2C_MOT) {
	case DP_AUX_I2C_WRITE:
	case DP_AUX_I2C_READ:
	value = DPAUX_DP_AUXCTL_CMD_ADDRESS_ONLY;
	break;

	default:
	return -EINVAL;
	}
	} else {
	/* For non-zero-sized messages, set the CMDLEN field. */
	value = DPAUX_DP_AUXCTL_CMDLEN(msg->size - 1);
	}

	switch (msg->request & ~DP_AUX_I2C_MOT) {
	case DP_AUX_I2C_WRITE:
	if (msg->request & DP_AUX_I2C_MOT)
	value \|= DPAUX_DP_AUXCTL_CMD_MOT_WR;
	else
	value \|= DPAUX_DP_AUXCTL_CMD_I2C_WR;

	break;

	case DP_AUX_I2C_READ:
	if (msg->request & DP_AUX_I2C_MOT)
	value \|= DPAUX_DP_AUXCTL_CMD_MOT_RD;
	else
	value \|= DPAUX_DP_AUXCTL_CMD_I2C_RD;

	break;

	case DP_AUX_I2C_STATUS:
	if (msg->request & DP_AUX_I2C_MOT)
	value \|= DPAUX_DP_AUXCTL_CMD_MOT_RQ;
	else
	value \|= DPAUX_DP_AUXCTL_CMD_I2C_RQ;

	break;

	case DP_AUX_NATIVE_WRITE:
	value \|= DPAUX_DP_AUXCTL_CMD_AUX_WR;
	break;

	case DP_AUX_NATIVE_READ:
	value \|= DPAUX_DP_AUXCTL_CMD_AUX_RD;
	break;

	default:
	return -EINVAL;
	}

	tegra_dpaux_writel(dpaux, msg->address, DPAUX_DP_AUXADDR);
	tegra_dpaux_writel(dpaux, value, DPAUX_DP_AUXCTL);

	if ((msg->request & DP_AUX_I2C_READ) == 0) {
	tegra_dpaux_write_fifo(dpaux, msg->buffer, msg->size);
	ret = msg->size;
	}

	/* start transaction */
	value = tegra_dpaux_readl(dpaux, DPAUX_DP_AUXCTL);
	value \|= DPAUX_DP_AUXCTL_TRANSACTREQ;
	tegra_dpaux_writel(dpaux, value, DPAUX_DP_AUXCTL);

	status = wait_for_completion_timeout(&dpaux->complete, timeout);
	if (!status)
	return -ETIMEDOUT;

	/* read status and clear errors */
	value = tegra_dpaux_readl(dpaux, DPAUX_DP_AUXSTAT);
	tegra_dpaux_writel(dpaux, 0xf00, DPAUX_DP_AUXSTAT);

	if (value & DPAUX_DP_AUXSTAT_TIMEOUT_ERROR)
	return -ETIMEDOUT;

	if ((value & DPAUX_DP_AUXSTAT_RX_ERROR) \|\|
	(value & DPAUX_DP_AUXSTAT_SINKSTAT_ERROR) \|\|
	(value & DPAUX_DP_AUXSTAT_NO_STOP_ERROR))
	return -EIO;

	switch ((value & DPAUX_DP_AUXSTAT_REPLY_TYPE_MASK) >> 16) {
	case 0x00:
	msg->reply = DP_AUX_NATIVE_REPLY_ACK;
	break;

	case 0x01:
	msg->reply = DP_AUX_NATIVE_REPLY_NACK;
	break;

	case 0x02:
	msg->reply = DP_AUX_NATIVE_REPLY_DEFER;
	break;

	case 0x04:
	msg->reply = DP_AUX_I2C_REPLY_NACK;
	break;

	case 0x08:
	msg->reply = DP_AUX_I2C_REPLY_DEFER;
	break;
	}

	if ((msg->size > 0) && (msg->reply == DP_AUX_NATIVE_REPLY_ACK)) {
	if (msg->request & DP_AUX_I2C_READ) {
	size_t count = value & DPAUX_DP_AUXSTAT_REPLY_MASK;

	if (WARN_ON(count != msg->size))
	count = min_t(size_t, count, msg->size);

	tegra_dpaux_read_fifo(dpaux, msg->buffer, count);
	ret = count;
	}
	}

	return ret;
	}

	static void tegra_dpaux_hotplug(struct work_struct *work)
	{
	struct tegra_dpaux *dpaux = work_to_dpaux(work);

	if (dpaux->output)
	drm_helper_hpd_irq_event(dpaux->output->connector.dev);
	}

	static irqreturn_t tegra_dpaux_irq(int irq, void *data)
	{
	struct tegra_dpaux *dpaux = data;
	irqreturn_t ret = IRQ_HANDLED;
	unsigned long value;

	/* clear interrupts */
	value = tegra_dpaux_readl(dpaux, DPAUX_INTR_AUX);
	tegra_dpaux_writel(dpaux, value, DPAUX_INTR_AUX);

	if (value & (DPAUX_INTR_PLUG_EVENT \| DPAUX_INTR_UNPLUG_EVENT))
	schedule_work(&dpaux->work);

	if (value & DPAUX_INTR_IRQ_EVENT) {
	/* TODO: handle this */
	}

	if (value & DPAUX_INTR_AUX_DONE)
	complete(&dpaux->complete);

	return ret;
	}

	static int tegra_dpaux_probe(struct platform_device *pdev)
	{
	struct tegra_dpaux *dpaux;
	struct resource *regs;
	unsigned long value;
	int err;

	dpaux = devm_kzalloc(&pdev->dev, sizeof(*dpaux), GFP_KERNEL);
	if (!dpaux)
	return -ENOMEM;

	INIT_WORK(&dpaux->work, tegra_dpaux_hotplug);
	init_completion(&dpaux->complete);
	INIT_LIST_HEAD(&dpaux->list);
	dpaux->dev = &pdev->dev;

	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	dpaux->regs = devm_ioremap_resource(&pdev->dev, regs);
	if (IS_ERR(dpaux->regs))
	return PTR_ERR(dpaux->regs);

	dpaux->irq = platform_get_irq(pdev, 0);
	if (dpaux->irq < 0) {
	dev_err(&pdev->dev, "failed to get IRQ\n");
	return -ENXIO;
	}

	dpaux->rst = devm_reset_control_get(&pdev->dev, "dpaux");
	if (IS_ERR(dpaux->rst))
	return PTR_ERR(dpaux->rst);

	dpaux->clk = devm_clk_get(&pdev->dev, NULL);
	if (IS_ERR(dpaux->clk))
	return PTR_ERR(dpaux->clk);

	err = clk_prepare_enable(dpaux->clk);
	if (err < 0)
	return err;

	reset_control_deassert(dpaux->rst);

	dpaux->clk_parent = devm_clk_get(&pdev->dev, "parent");
	if (IS_ERR(dpaux->clk_parent))
	return PTR_ERR(dpaux->clk_parent);

	err = clk_prepare_enable(dpaux->clk_parent);
	if (err < 0)
	return err;

	err = clk_set_rate(dpaux->clk_parent, 270000000);
	if (err < 0) {
	dev_err(&pdev->dev, "failed to set clock to 270 MHz: %d\n",
	err);
	return err;
	}

	dpaux->vdd = devm_regulator_get(&pdev->dev, "vdd");
	if (IS_ERR(dpaux->vdd))
	return PTR_ERR(dpaux->vdd);

	err = devm_request_irq(dpaux->dev, dpaux->irq, tegra_dpaux_irq, 0,
	dev_name(dpaux->dev), dpaux);
	if (err < 0) {
	dev_err(dpaux->dev, "failed to request IRQ#%u: %d\n",
	dpaux->irq, err);
	return err;
	}

	dpaux->aux.transfer = tegra_dpaux_transfer;
	dpaux->aux.dev = &pdev->dev;

	err = drm_dp_aux_register(&dpaux->aux);
	if (err < 0)
	return err;

	/* enable and clear all interrupts */
	value = DPAUX_INTR_AUX_DONE \| DPAUX_INTR_IRQ_EVENT \|
	DPAUX_INTR_UNPLUG_EVENT \| DPAUX_INTR_PLUG_EVENT;
	tegra_dpaux_writel(dpaux, value, DPAUX_INTR_EN_AUX);
	tegra_dpaux_writel(dpaux, value, DPAUX_INTR_AUX);

	mutex_lock(&dpaux_lock);
	list_add_tail(&dpaux->list, &dpaux_list);
	mutex_unlock(&dpaux_lock);

	platform_set_drvdata(pdev, dpaux);

	return 0;
	}

	static int tegra_dpaux_remove(struct platform_device *pdev)
	{
	struct tegra_dpaux *dpaux = platform_get_drvdata(pdev);

	drm_dp_aux_unregister(&dpaux->aux);

	mutex_lock(&dpaux_lock);
	list_del(&dpaux->list);
	mutex_unlock(&dpaux_lock);

	cancel_work_sync(&dpaux->work);

	clk_disable_unprepare(dpaux->clk_parent);
	reset_control_assert(dpaux->rst);
	clk_disable_unprepare(dpaux->clk);

	return 0;
	}

	static const struct of_device_id tegra_dpaux_of_match[] = {
	{ .compatible = "nvidia,tegra124-dpaux", },
	{ },
	};
	MODULE_DEVICE_TABLE(of, tegra_dpaux_of_match);

	struct platform_driver tegra_dpaux_driver = {
	.driver = {
	.name = "tegra-dpaux",
	.of_match_table = tegra_dpaux_of_match,
	},
	.probe = tegra_dpaux_probe,
	.remove = tegra_dpaux_remove,
	};

	struct tegra_dpaux tegra_dpaux_find_by_of_node(struct device_node np)
	{
	struct tegra_dpaux *dpaux;

	mutex_lock(&dpaux_lock);

	list_for_each_entry(dpaux, &dpaux_list, list)
	if (np == dpaux->dev->of_node) {
	mutex_unlock(&dpaux_lock);
	return dpaux;
	}

	mutex_unlock(&dpaux_lock);

	return NULL;
	}

	int tegra_dpaux_attach(struct tegra_dpaux dpaux, struct tegra_output output)
	{
	unsigned long timeout;
	int err;

	output->connector.polled = DRM_CONNECTOR_POLL_HPD;
	dpaux->output = output;

	err = regulator_enable(dpaux->vdd);
	if (err < 0)
	return err;

	timeout = jiffies + msecs_to_jiffies(250);

	while (time_before(jiffies, timeout)) {
	enum drm_connector_status status;

	status = tegra_dpaux_detect(dpaux);
	if (status == connector_status_connected)
	return 0;

	usleep_range(1000, 2000);
	}

	return -ETIMEDOUT;
	}

	int tegra_dpaux_detach(struct tegra_dpaux *dpaux)
	{
	unsigned long timeout;
	int err;

	err = regulator_disable(dpaux->vdd);
	if (err < 0)
	return err;

	timeout = jiffies + msecs_to_jiffies(250);

	while (time_before(jiffies, timeout)) {
	enum drm_connector_status status;

	status = tegra_dpaux_detect(dpaux);
	if (status == connector_status_disconnected) {
	dpaux->output = NULL;
	return 0;
	}

	usleep_range(1000, 2000);
	}

	return -ETIMEDOUT;
	}

	enum drm_connector_status tegra_dpaux_detect(struct tegra_dpaux *dpaux)
	{
	unsigned long value;

	value = tegra_dpaux_readl(dpaux, DPAUX_DP_AUXSTAT);

	if (value & DPAUX_DP_AUXSTAT_HPD_STATUS)
	return connector_status_connected;

	return connector_status_disconnected;
	}

	int tegra_dpaux_enable(struct tegra_dpaux *dpaux)
	{
	unsigned long value;

	value = DPAUX_HYBRID_PADCTL_AUX_CMH(2) \|
	DPAUX_HYBRID_PADCTL_AUX_DRVZ(4) \|
	DPAUX_HYBRID_PADCTL_AUX_DRVI(0x18) \|
	DPAUX_HYBRID_PADCTL_AUX_INPUT_RCV \|
	DPAUX_HYBRID_PADCTL_MODE_AUX;
	tegra_dpaux_writel(dpaux, value, DPAUX_HYBRID_PADCTL);

	value = tegra_dpaux_readl(dpaux, DPAUX_HYBRID_SPARE);
	value &= ~DPAUX_HYBRID_SPARE_PAD_POWER_DOWN;
	tegra_dpaux_writel(dpaux, value, DPAUX_HYBRID_SPARE);

	return 0;
	}

	int tegra_dpaux_disable(struct tegra_dpaux *dpaux)
	{
	unsigned long value;

	value = tegra_dpaux_readl(dpaux, DPAUX_HYBRID_SPARE);
	value \|= DPAUX_HYBRID_SPARE_PAD_POWER_DOWN;
	tegra_dpaux_writel(dpaux, value, DPAUX_HYBRID_SPARE);

	return 0;
	}

	int tegra_dpaux_prepare(struct tegra_dpaux *dpaux, u8 encoding)
	{
	int err;

	err = drm_dp_dpcd_writeb(&dpaux->aux, DP_MAIN_LINK_CHANNEL_CODING_SET,
	encoding);
	if (err < 0)
	return err;

	return 0;
	}

	int tegra_dpaux_train(struct tegra_dpaux dpaux, struct drm_dp_link link,
	u8 pattern)
	{
	u8 tp = pattern & DP_TRAINING_PATTERN_MASK;
	u8 status[DP_LINK_STATUS_SIZE], values[4];
	unsigned int i;
	int err;

	err = drm_dp_dpcd_writeb(&dpaux->aux, DP_TRAINING_PATTERN_SET, pattern);
	if (err < 0)
	return err;

	if (tp == DP_TRAINING_PATTERN_DISABLE)
	return 0;

	for (i = 0; i < link->num_lanes; i++)
	values[i] = DP_TRAIN_MAX_PRE_EMPHASIS_REACHED \|
	DP_TRAIN_PRE_EMPH_LEVEL_0 \|
	DP_TRAIN_MAX_SWING_REACHED \|
	DP_TRAIN_VOLTAGE_SWING_LEVEL_0;

	err = drm_dp_dpcd_write(&dpaux->aux, DP_TRAINING_LANE0_SET, values,
	link->num_lanes);
	if (err < 0)
	return err;

	usleep_range(500, 1000);

	err = drm_dp_dpcd_read_link_status(&dpaux->aux, status);
	if (err < 0)
	return err;

	switch (tp) {
	case DP_TRAINING_PATTERN_1:
	if (!drm_dp_clock_recovery_ok(status, link->num_lanes))
	return -EAGAIN;

	break;

	case DP_TRAINING_PATTERN_2:
	if (!drm_dp_channel_eq_ok(status, link->num_lanes))
	return -EAGAIN;

	break;

	default:
	dev_err(dpaux->dev, "unsupported training pattern %u\n", tp);
	return -EINVAL;
	}

	err = drm_dp_dpcd_writeb(&dpaux->aux, DP_EDP_CONFIGURATION_SET, 0);
	if (err < 0)
	return err;

	return 0;
	}