touch_bus_negotiator.c - kernel/google-modules/touch/common - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Touch Bus Negotiator for Google Pixel devices.
  *
  * Copyright (C) 2021 Google, Inc.
  */

 #include <linux/module.h>
 #include <linux/platform_device.h>
 #include <linux/net.h>
 #include <linux/printk.h>
 #include <linux/slab.h>
 #include <linux/gpio.h>
 #include <linux/interrupt.h>
 #include <linux/irq.h>
 #include <linux/of_gpio.h>
 #include <linux/delay.h>
 #include "touch_bus_negotiator.h"

 #if IS_ENABLED(CONFIG_TOUCHSCREEN_TBN_AOC_CHANNEL_MODE)
 #include <uapi/linux/sched/types.h>
 #include "aoc_tbn_service_dev.h"
 #endif

 #define TBN_MODULE_NAME "touch_bus_negotiator"
 #define TBN_AOC_CHANNEL_THREAD_NAME "tbn_aoc_channel"

 #if IS_ENABLED(CONFIG_TOUCHSCREEN_TBN_AOC_CHANNEL_MODE)
 static void handle_tbn_event_response(struct tbn_context *tbn,
 	struct TbnEventResponse *response);
 #endif

 static struct tbn_context *tbn_context;

 static irqreturn_t tbn_aoc2ap_irq_thread(int irq, void *ptr)
 {
 	struct tbn_context *tbn = ptr;

 	dev_info(tbn->dev, "%s: bus_released:%d bus_requested:%d.\n", __func__,
 		completion_done(&tbn->bus_released), completion_done(&tbn->bus_requested));

 	if (completion_done(&tbn->bus_released) && completion_done(&tbn->bus_requested))
 		return IRQ_HANDLED;

 	/*
 	 * For bus release, there two possibilities:
 	 * 1. aoc2ap gpio value already changed to AOC
 	 * 2. tbn_release_bus() with TBN_RELEASE_BUS_TIMEOUT_MS timeout
 	 *    for complete_all(&tbn->bus_released);
 	 */
 	while (!completion_done(&tbn->bus_released)) {
 		if (gpio_get_value(tbn->aoc2ap_gpio) == TBN_BUS_OWNER_AOC)
 			complete_all(&tbn->bus_released);
 		else
 			usleep_range(10000, 10000);	/* wait 10 ms for gpio stablized */
 	}

 	/*
 	 * For bus request, there two possibilities:
 	 * 1. aoc2ap gpio value already changed to AP
 	 * 2. tbn_request_bus() with TBN_REQUEST_BUS_TIMEOUT_MS timeout
 	 *    for complete_all(&tbn->bus_requested);
 	 */
 	while (!completion_done(&tbn->bus_requested)) {
 		if (gpio_get_value(tbn->aoc2ap_gpio) == TBN_BUS_OWNER_AP)
 			complete_all(&tbn->bus_requested);
 		else
 			usleep_range(10000, 10000);	/* wait 10 ms for gpio stablized */
 	}

 	return IRQ_HANDLED;
 }

 #if IS_ENABLED(CONFIG_TOUCHSCREEN_TBN_AOC_CHANNEL_MODE)
 static int aoc_channel_kthread(void *data)
 {
 	struct tbn_context *tbn = data;
 	struct TbnEventResponse resp;
 	ssize_t len;
 	bool service_ready = false;

 	while (!kthread_should_stop()) {
 		if (service_ready != aoc_tbn_service_ready()) {
 			service_ready = !service_ready;
 			dev_info(tbn->dev, "%s: AOC TBN service is %s.\n",
 				__func__, service_ready ? "ready" : "not ready");
 		}

 		if (!service_ready) {
 			msleep(1000);
 			continue;
 		}

 		len = aoc_tbn_service_read(&resp, sizeof(resp));
 		if (len < 0) {
 			dev_err(tbn->dev, "%s: failed to read message, err: %d\n",
 				__func__, len);
 			msleep(1000);
 			continue;
 		}

 		if (kthread_should_stop()) {
 			break;
 		}

 		if (len == sizeof(resp)) {
 			handle_tbn_event_response(tbn, &resp);
 		}
 	}

 	return 0;
 }

 static void handle_tbn_event_response(struct tbn_context *tbn,
 	struct TbnEventResponse *response)
 {
 	mutex_lock(&tbn->event_lock);

 	if (response->id != tbn->event.id) {
 		dev_err(tbn->dev,
 			"%s: receive wrong response, id: %d, expected id: %d, "
 			"bus_released:%d bus_requested:%d.\n",
 			__func__, response->id, tbn->event.id,
 			completion_done(&tbn->bus_released),
 			completion_done(&tbn->bus_requested));
 		goto exit;
 	}

 	if (response->err != 0) {
 		dev_err(tbn->dev, "%s: send tbn event failed, err %d!\n",
 			__func__, response->err);
 		tbn->event_resp.err = response->err;
 	} else {
 		tbn->event_resp.lptw_triggered = response->lptw_triggered;
 	}

 	if (response->operation == TBN_OPERATION_AP_REQUEST_BUS) {
 		complete_all(&tbn->bus_requested);
 	} else if (response->operation == TBN_OPERATION_AP_RELEASE_BUS) {
 		complete_all(&tbn->bus_released);
 	} else {
 		dev_err(tbn->dev, "%s: response unknown operation, op: %d!\n",
 			__func__, response->operation);
 	}

 exit:
 	mutex_unlock(&tbn->event_lock);
 }

 static void send_tbn_event(struct tbn_context *tbn, enum TbnOperation operation)
 {
 	ssize_t len;
 	int retry = 3;

 	if (!aoc_tbn_service_ready()) {
 		dev_err(tbn_context->dev, "%s: AOC TBN service is not ready.\n",
 			__func__);
 		return;
 	}

 	mutex_lock(&tbn->event_lock);

 	tbn->event.operation = operation;
 	tbn->event.id++;

 	while (retry) {
 		len = aoc_tbn_service_write(&tbn->event, sizeof(tbn->event));
 		if (len == sizeof(tbn->event)) {
 			break;
 		}
 		dev_err(tbn_context->dev, "%s: failed to send TBN event, retry: %d.\n",
 			__func__, retry);
 		retry--;
 	}

 	mutex_unlock(&tbn->event_lock);
 }
 #endif

 int tbn_handshaking(struct tbn_context *tbn, enum TbnOperation operation)
 {
 	struct completion *wait_for_completion;
 	enum tbn_bus_owner bus_owner;
 	unsigned int irq_type;
 	unsigned int timeout;
 	const char *msg;
 	int ret = 0;

 	if (!tbn || tbn->registered_mask == 0) {
 		dev_err(tbn_context->dev, "%s: tbn is not ready to serve.\n", __func__);
 		return -EINVAL;
 	}

 	if (operation == TBN_OPERATION_AP_REQUEST_BUS) {
 		wait_for_completion = &tbn->bus_requested;
 		bus_owner = TBN_BUS_OWNER_AP;
 		irq_type = IRQF_TRIGGER_FALLING;
 		timeout = TBN_REQUEST_BUS_TIMEOUT_MS;
 		msg = "request";
 	} else if (operation == TBN_OPERATION_AP_RELEASE_BUS) {
 		wait_for_completion = &tbn->bus_released;
 		bus_owner = TBN_BUS_OWNER_AOC;
 		irq_type = IRQF_TRIGGER_RISING;
 		timeout = TBN_RELEASE_BUS_TIMEOUT_MS;
 		msg = "release";
 	} else {
 		dev_err(tbn_context->dev, "%s: request unknown operation, op: %d.\n",
 			__func__, operation);
 		return -EINVAL;
 	}

 	if (tbn->mode == TBN_MODE_GPIO) {
 		int ap2aoc_val_org = gpio_get_value(tbn->ap2aoc_gpio);
 		int aoc2ap_val_org = gpio_get_value(tbn->aoc2ap_gpio);

 		reinit_completion(wait_for_completion);

 		irq_set_irq_type(tbn->aoc2ap_irq, irq_type);
 		enable_irq(tbn->aoc2ap_irq);
 		gpio_direction_output(tbn->ap2aoc_gpio, bus_owner);
 		if (wait_for_completion_timeout(wait_for_completion,
 			msecs_to_jiffies(timeout)) == 0) {
 			int ap2aoc_val = gpio_get_value(tbn->ap2aoc_gpio);
 			int aoc2ap_val = gpio_get_value(tbn->aoc2ap_gpio);

 			complete_all(wait_for_completion);
 			if (bus_owner == aoc2ap_val)
 				ret = 0;
 			else
 				ret = -ETIMEDOUT;
 			dev_err(tbn->dev, "AP %s bus ... timeout!, ap2aoc_gpio(B:%d,A:%d)"
 				" aoc2ap_gpio(B:%d,A:%d), ret=%d\n",
 				msg, ap2aoc_val_org, ap2aoc_val, aoc2ap_val_org,
 				aoc2ap_val, ret);
 		} else
 			dev_info(tbn->dev, "AP %s bus ... SUCCESS!\n", msg);
 		disable_irq_nosync(tbn->aoc2ap_irq);
 #if IS_ENABLED(CONFIG_TOUCHSCREEN_TBN_AOC_CHANNEL_MODE)
 	} else if (tbn->mode == TBN_MODE_AOC_CHANNEL) {
 		tbn->event_resp.lptw_triggered = false;
 		tbn->event_resp.err = 0;

 		reinit_completion(wait_for_completion);

 		send_tbn_event(tbn, operation);
 		if (wait_for_completion_timeout(wait_for_completion,
 			msecs_to_jiffies(timeout)) == 0) {
 			dev_err(tbn->dev, "AP %s bus ... timeout!\n", msg);
 			complete_all(wait_for_completion);
 			ret = -ETIMEDOUT;
 		} else {
 			if (tbn->event_resp.err == 0) {
 				dev_info(tbn->dev, "AP %s bus ... SUCCESS!\n", msg);
 			} else {
 				dev_info(tbn->dev, "AP %s bus ... failed!\n", msg);
 				ret = -EBUSY;
 			}
 		}
 #endif
 	} else if (tbn->mode == TBN_MODE_MOCK) {
 		dev_info(tbn->dev, "AP %s bus ... SUCCESS!\n", msg);
 	} else {
 		ret = -EINVAL;
 	}

 	return ret;
 }

 int tbn_request_bus_with_result(u32 dev_mask, bool *lptw_triggered)
 {
 	int ret = 0;

 	if (!tbn_context)
 		return -ENODEV;

 	mutex_lock(&tbn_context->dev_mask_mutex);

 	if ((dev_mask & tbn_context->registered_mask) == 0) {
 		mutex_unlock(&tbn_context->dev_mask_mutex);
 		dev_err(tbn_context->dev, "%s: dev_mask %#x is invalid.\n",
 			__func__, dev_mask);
 		return -EINVAL;
 	}

 	if (tbn_context->requested_dev_mask == 0) {
 		ret = tbn_handshaking(tbn_context, TBN_OPERATION_AP_REQUEST_BUS);
 		if ((ret == 0) && (lptw_triggered != NULL))
 			*lptw_triggered = tbn_context->event_resp.lptw_triggered;
 	} else {
 		dev_dbg(tbn_context->dev,
 			"%s: Bus already requested, requested_dev_mask %#x dev_mask %#x.\n",
 			__func__, tbn_context->requested_dev_mask, dev_mask);
 	}
 	tbn_context->requested_dev_mask |= dev_mask;

 	mutex_unlock(&tbn_context->dev_mask_mutex);

 	return ret;
 }
 EXPORT_SYMBOL_GPL(tbn_request_bus_with_result);

 int tbn_request_bus(u32 dev_mask)
 {
 	return tbn_request_bus_with_result(dev_mask, NULL);
 }
 EXPORT_SYMBOL_GPL(tbn_request_bus);

 int tbn_release_bus(u32 dev_mask)
 {
 	int ret = 0;

 	if (!tbn_context)
 		return -ENODEV;

 	mutex_lock(&tbn_context->dev_mask_mutex);

 	if ((dev_mask & tbn_context->registered_mask) == 0) {
 		mutex_unlock(&tbn_context->dev_mask_mutex);
 		dev_err(tbn_context->dev, "%s: dev_mask %#x is invalid.\n",
 			__func__, dev_mask);
 		return -EINVAL;
 	}

 	if (tbn_context->requested_dev_mask == 0) {
 		dev_warn(tbn_context->dev,
 			 "%s: Bus already released, dev_mask %#x.\n",
 			 __func__, dev_mask);
 		mutex_unlock(&tbn_context->dev_mask_mutex);
 		return 0;
 	}

 	/* Release the bus when the last requested_dev_mask bit releases. */
 	if (tbn_context->requested_dev_mask == dev_mask) {
 		ret = tbn_handshaking(tbn_context, TBN_OPERATION_AP_RELEASE_BUS);
 	} else {
 		dev_dbg(tbn_context->dev,
 			 "%s: Bus is still in use, requested_dev_mask %#x dev_mask %#x.\n",
 			 __func__, tbn_context->requested_dev_mask, dev_mask);
 	}

 	tbn_context->requested_dev_mask &= ~dev_mask;

 	mutex_unlock(&tbn_context->dev_mask_mutex);

 	return ret;
 }
 EXPORT_SYMBOL_GPL(tbn_release_bus);

 int register_tbn(u32 *output)
 {
 	u32 i = 0;

 	*output = 0;

 	if (!tbn_context) {
 		pr_warn("%s: tbn_context doesn't exist.", __func__);
 		return 0;
 	}

 	mutex_lock(&tbn_context->dev_mask_mutex);
 	for (i = 0; i < tbn_context->max_devices; i++) {
 		if (tbn_context->registered_mask & BIT_MASK(i))
 			continue;
 		tbn_context->registered_mask |= BIT_MASK(i);
 		/* Assume screen is on while registering tbn. */
 		tbn_context->requested_dev_mask |= BIT_MASK(i);
 		*output = BIT_MASK(i);
 		break;
 	}

 	mutex_unlock(&tbn_context->dev_mask_mutex);

 	return 0;
 }
 EXPORT_SYMBOL_GPL(register_tbn);

 void unregister_tbn(u32 *output)
 {
 	if (!tbn_context)
 		return ;

 	mutex_lock(&tbn_context->dev_mask_mutex);
 	tbn_context->registered_mask &= ~(*output);
 	*output = 0;
 	mutex_unlock(&tbn_context->dev_mask_mutex);
 }
 EXPORT_SYMBOL_GPL(unregister_tbn);

 static int tbn_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	struct tbn_context *tbn = NULL;
 	struct device_node *np = dev->of_node;
 	int err = 0;
 #if IS_ENABLED(CONFIG_TOUCHSCREEN_TBN_AOC_CHANNEL_MODE)
 	struct sched_param param = {
 		.sched_priority = 10,
 	};
 #endif


 	tbn = devm_kzalloc(dev, sizeof(struct tbn_context), GFP_KERNEL);
 	if (!tbn)
 		goto failed;

 	tbn->dev = dev;
 	tbn->event_resp.lptw_triggered = false;
 	tbn_context = tbn;
 	dev_set_drvdata(tbn->dev, tbn);

 	if (of_property_read_u32(np, "tbn,max_devices", &tbn->max_devices))
 		tbn->max_devices = 1;

 	err = of_property_read_u32(np, "tbn,mode", &tbn->mode);
 	if (err)
 		tbn->mode = TBN_MODE_GPIO;

 	if (tbn->mode == TBN_MODE_GPIO) {
 		tbn->ap2aoc_gpio = of_get_named_gpio(np, "tbn,ap2aoc_gpio", 0);
 		if (gpio_is_valid(tbn->ap2aoc_gpio)) {
 			err = devm_gpio_request_one(tbn->dev, tbn->ap2aoc_gpio,
 				GPIOF_OUT_INIT_LOW, "tbn,ap2aoc_gpio");
 			if (err) {
 				dev_err(tbn->dev, "%s: Unable to request ap2aoc_gpio %d, err %d!\n",
 					__func__, tbn->ap2aoc_gpio, err);
 				goto failed;
 			}
 		} else {
 			dev_err(tbn->dev, "%s: invalid ap2aoc_gpio %d!\n",
 				__func__, tbn->ap2aoc_gpio);
 			err = -EPROBE_DEFER;
 			goto failed;
 		}

 		tbn->aoc2ap_gpio = of_get_named_gpio(np, "tbn,aoc2ap_gpio", 0);
 		if (gpio_is_valid(tbn->aoc2ap_gpio)) {
 			err = devm_gpio_request_one(tbn->dev, tbn->aoc2ap_gpio,
 				GPIOF_DIR_IN, "tbn,aoc2ap_gpio");
 			if (err) {
 				dev_err(tbn->dev, "%s: Unable to request aoc2ap_gpio %d, err %d!\n",
 					__func__, tbn->aoc2ap_gpio, err);
 				goto failed;
 			}
 			tbn->aoc2ap_irq = gpio_to_irq(tbn->aoc2ap_gpio);
 			err = devm_request_threaded_irq(tbn->dev,
 				tbn->aoc2ap_irq, NULL,
 				tbn_aoc2ap_irq_thread,
 				IRQF_TRIGGER_RISING |
 				IRQF_ONESHOT, "tbn", tbn);
 			if (err) {
 				dev_err(tbn->dev,
 					"%s: Unable to request_threaded_irq, err %d!\n",
 					__func__, err);
 				goto failed;
 			}
 			disable_irq_nosync(tbn->aoc2ap_irq);
 		} else {
 			dev_err(tbn->dev, "%s: invalid aoc2ap_gpio %d!\n",
 				__func__, tbn->aoc2ap_gpio);
 			err = -EPROBE_DEFER;
 			goto failed;
 		}

 		dev_info(tbn->dev,
 			"%s: gpios(aoc2ap: %d ap2aoc: %d)\n",
 			__func__, tbn->aoc2ap_gpio, tbn->ap2aoc_gpio);
 #if IS_ENABLED(CONFIG_TOUCHSCREEN_TBN_AOC_CHANNEL_MODE)
 	} else if (tbn->mode == TBN_MODE_AOC_CHANNEL) {
 		mutex_init(&tbn->event_lock);

 		tbn->aoc_channel_task = kthread_run(&aoc_channel_kthread, tbn,
 			TBN_AOC_CHANNEL_THREAD_NAME);
 		if (IS_ERR(tbn->aoc_channel_task)) {
 			err = PTR_ERR(tbn->aoc_channel_task);
 			goto failed;
 		}

 		err = sched_setscheduler(tbn->aoc_channel_task, SCHED_FIFO, &param);
 		if (err != 0) {
 			goto failed;
 		}
 #endif
 	} else if (tbn->mode == TBN_MODE_MOCK) {
 		err = 0;
 	} else {
 		dev_err(tbn->dev, "bus negotiator: invalid mode: %d\n", tbn->mode);
 		err = -EINVAL;
 		goto failed;
 	}

 	mutex_init(&tbn->dev_mask_mutex);

 	init_completion(&tbn->bus_requested);
 	init_completion(&tbn->bus_released);
 	complete_all(&tbn->bus_requested);
 	complete_all(&tbn->bus_released);

 	dev_info(tbn->dev, "bus negotiator initialized: %pK, mode: %d\n", tbn, tbn->mode);

 failed:
 	if (err) {
 		devm_kfree(dev, tbn);
 		tbn_context = NULL;
 	}

 	return err;
 }

 static int tbn_remove(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	struct tbn_context *tbn = dev_get_drvdata(dev);

 	if (tbn->mode == TBN_MODE_GPIO) {
 		free_irq(tbn->aoc2ap_irq, tbn);
 		if (gpio_is_valid(tbn->aoc2ap_gpio))
 			gpio_free(tbn->aoc2ap_gpio);
 		if (gpio_is_valid(tbn->aoc2ap_gpio))
 			gpio_free(tbn->aoc2ap_gpio);
 #if IS_ENABLED(CONFIG_TOUCHSCREEN_TBN_AOC_CHANNEL_MODE)
 	} else if (tbn->mode == TBN_MODE_AOC_CHANNEL) {
 		kthread_stop(tbn->aoc_channel_task);
 #endif
 	}
 	return 0;
 }

 static struct of_device_id tbn_of_match_table[] = {
 	{
 		.compatible = TBN_MODULE_NAME,
 	},
 	{},
 };

 static struct platform_driver tbn_driver = {
 	.driver = {
 		.name = TBN_MODULE_NAME,
 		.of_match_table = tbn_of_match_table,
 	},
 	.probe = tbn_probe,
 	.remove = tbn_remove,
 };

 static int __init tbn_init(void)
 {
 	return platform_driver_register(&tbn_driver);
 }

 static void __exit tbn_exit(void)
 {
 	platform_driver_unregister(&tbn_driver);
 }
 module_init(tbn_init);
 module_exit(tbn_exit);

 MODULE_SOFTDEP("pre: touch_offload");
 MODULE_LICENSE("GPL v2");
 MODULE_DESCRIPTION("Touch Bus Negotiator");
 MODULE_AUTHOR("Google, Inc.");
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Touch Bus Negotiator for Google Pixel devices.
	*
	* Copyright (C) 2021 Google, Inc.
	*/

	#include <linux/module.h>
	#include <linux/platform_device.h>
	#include <linux/net.h>
	#include <linux/printk.h>
	#include <linux/slab.h>
	#include <linux/gpio.h>
	#include <linux/interrupt.h>
	#include <linux/irq.h>
	#include <linux/of_gpio.h>
	#include <linux/delay.h>
	#include "touch_bus_negotiator.h"

	#if IS_ENABLED(CONFIG_TOUCHSCREEN_TBN_AOC_CHANNEL_MODE)
	#include <uapi/linux/sched/types.h>
	#include "aoc_tbn_service_dev.h"
	#endif

	#define TBN_MODULE_NAME "touch_bus_negotiator"
	#define TBN_AOC_CHANNEL_THREAD_NAME "tbn_aoc_channel"

	#if IS_ENABLED(CONFIG_TOUCHSCREEN_TBN_AOC_CHANNEL_MODE)
	static void handle_tbn_event_response(struct tbn_context *tbn,
	struct TbnEventResponse *response);
	#endif

	static struct tbn_context *tbn_context;

	static irqreturn_t tbn_aoc2ap_irq_thread(int irq, void *ptr)
	{
	struct tbn_context *tbn = ptr;

	dev_info(tbn->dev, "%s: bus_released:%d bus_requested:%d.\n", __func__,
	completion_done(&tbn->bus_released), completion_done(&tbn->bus_requested));

	if (completion_done(&tbn->bus_released) && completion_done(&tbn->bus_requested))
	return IRQ_HANDLED;

	/*
	* For bus release, there two possibilities:
	* 1. aoc2ap gpio value already changed to AOC
	* 2. tbn_release_bus() with TBN_RELEASE_BUS_TIMEOUT_MS timeout
	* for complete_all(&tbn->bus_released);
	*/
	while (!completion_done(&tbn->bus_released)) {
	if (gpio_get_value(tbn->aoc2ap_gpio) == TBN_BUS_OWNER_AOC)
	complete_all(&tbn->bus_released);
	else
	usleep_range(10000, 10000); /* wait 10 ms for gpio stablized */
	}

	/*
	* For bus request, there two possibilities:
	* 1. aoc2ap gpio value already changed to AP
	* 2. tbn_request_bus() with TBN_REQUEST_BUS_TIMEOUT_MS timeout
	* for complete_all(&tbn->bus_requested);
	*/
	while (!completion_done(&tbn->bus_requested)) {
	if (gpio_get_value(tbn->aoc2ap_gpio) == TBN_BUS_OWNER_AP)
	complete_all(&tbn->bus_requested);
	else
	usleep_range(10000, 10000); /* wait 10 ms for gpio stablized */
	}

	return IRQ_HANDLED;
	}

	#if IS_ENABLED(CONFIG_TOUCHSCREEN_TBN_AOC_CHANNEL_MODE)
	static int aoc_channel_kthread(void *data)
	{
	struct tbn_context *tbn = data;
	struct TbnEventResponse resp;
	ssize_t len;
	bool service_ready = false;

	while (!kthread_should_stop()) {
	if (service_ready != aoc_tbn_service_ready()) {
	service_ready = !service_ready;
	dev_info(tbn->dev, "%s: AOC TBN service is %s.\n",
	__func__, service_ready ? "ready" : "not ready");
	}

	if (!service_ready) {
	msleep(1000);
	continue;
	}

	len = aoc_tbn_service_read(&resp, sizeof(resp));
	if (len < 0) {
	dev_err(tbn->dev, "%s: failed to read message, err: %d\n",
	__func__, len);
	msleep(1000);
	continue;
	}

	if (kthread_should_stop()) {
	break;
	}

	if (len == sizeof(resp)) {
	handle_tbn_event_response(tbn, &resp);
	}
	}

	return 0;
	}

	static void handle_tbn_event_response(struct tbn_context *tbn,
	struct TbnEventResponse *response)
	{
	mutex_lock(&tbn->event_lock);

	if (response->id != tbn->event.id) {
	dev_err(tbn->dev,
	"%s: receive wrong response, id: %d, expected id: %d, "
	"bus_released:%d bus_requested:%d.\n",
	__func__, response->id, tbn->event.id,
	completion_done(&tbn->bus_released),
	completion_done(&tbn->bus_requested));
	goto exit;
	}

	if (response->err != 0) {
	dev_err(tbn->dev, "%s: send tbn event failed, err %d!\n",
	__func__, response->err);
	tbn->event_resp.err = response->err;
	} else {
	tbn->event_resp.lptw_triggered = response->lptw_triggered;
	}

	if (response->operation == TBN_OPERATION_AP_REQUEST_BUS) {
	complete_all(&tbn->bus_requested);
	} else if (response->operation == TBN_OPERATION_AP_RELEASE_BUS) {
	complete_all(&tbn->bus_released);
	} else {
	dev_err(tbn->dev, "%s: response unknown operation, op: %d!\n",
	__func__, response->operation);
	}

	exit:
	mutex_unlock(&tbn->event_lock);
	}

	static void send_tbn_event(struct tbn_context *tbn, enum TbnOperation operation)
	{
	ssize_t len;
	int retry = 3;

	if (!aoc_tbn_service_ready()) {
	dev_err(tbn_context->dev, "%s: AOC TBN service is not ready.\n",
	__func__);
	return;
	}

	mutex_lock(&tbn->event_lock);

	tbn->event.operation = operation;
	tbn->event.id++;

	while (retry) {
	len = aoc_tbn_service_write(&tbn->event, sizeof(tbn->event));
	if (len == sizeof(tbn->event)) {
	break;
	}
	dev_err(tbn_context->dev, "%s: failed to send TBN event, retry: %d.\n",
	__func__, retry);
	retry--;
	}

	mutex_unlock(&tbn->event_lock);
	}
	#endif

	int tbn_handshaking(struct tbn_context *tbn, enum TbnOperation operation)
	{
	struct completion *wait_for_completion;
	enum tbn_bus_owner bus_owner;
	unsigned int irq_type;
	unsigned int timeout;
	const char *msg;
	int ret = 0;

	if (!tbn \|\| tbn->registered_mask == 0) {
	dev_err(tbn_context->dev, "%s: tbn is not ready to serve.\n", __func__);
	return -EINVAL;
	}

	if (operation == TBN_OPERATION_AP_REQUEST_BUS) {
	wait_for_completion = &tbn->bus_requested;
	bus_owner = TBN_BUS_OWNER_AP;
	irq_type = IRQF_TRIGGER_FALLING;
	timeout = TBN_REQUEST_BUS_TIMEOUT_MS;
	msg = "request";
	} else if (operation == TBN_OPERATION_AP_RELEASE_BUS) {
	wait_for_completion = &tbn->bus_released;
	bus_owner = TBN_BUS_OWNER_AOC;
	irq_type = IRQF_TRIGGER_RISING;
	timeout = TBN_RELEASE_BUS_TIMEOUT_MS;
	msg = "release";
	} else {
	dev_err(tbn_context->dev, "%s: request unknown operation, op: %d.\n",
	__func__, operation);
	return -EINVAL;
	}

	if (tbn->mode == TBN_MODE_GPIO) {
	int ap2aoc_val_org = gpio_get_value(tbn->ap2aoc_gpio);
	int aoc2ap_val_org = gpio_get_value(tbn->aoc2ap_gpio);

	reinit_completion(wait_for_completion);

	irq_set_irq_type(tbn->aoc2ap_irq, irq_type);
	enable_irq(tbn->aoc2ap_irq);
	gpio_direction_output(tbn->ap2aoc_gpio, bus_owner);
	if (wait_for_completion_timeout(wait_for_completion,
	msecs_to_jiffies(timeout)) == 0) {
	int ap2aoc_val = gpio_get_value(tbn->ap2aoc_gpio);
	int aoc2ap_val = gpio_get_value(tbn->aoc2ap_gpio);

	complete_all(wait_for_completion);
	if (bus_owner == aoc2ap_val)
	ret = 0;
	else
	ret = -ETIMEDOUT;
	dev_err(tbn->dev, "AP %s bus ... timeout!, ap2aoc_gpio(B:%d,A:%d)"
	" aoc2ap_gpio(B:%d,A:%d), ret=%d\n",
	msg, ap2aoc_val_org, ap2aoc_val, aoc2ap_val_org,
	aoc2ap_val, ret);
	} else
	dev_info(tbn->dev, "AP %s bus ... SUCCESS!\n", msg);
	disable_irq_nosync(tbn->aoc2ap_irq);
	#if IS_ENABLED(CONFIG_TOUCHSCREEN_TBN_AOC_CHANNEL_MODE)
	} else if (tbn->mode == TBN_MODE_AOC_CHANNEL) {
	tbn->event_resp.lptw_triggered = false;
	tbn->event_resp.err = 0;

	reinit_completion(wait_for_completion);

	send_tbn_event(tbn, operation);
	if (wait_for_completion_timeout(wait_for_completion,
	msecs_to_jiffies(timeout)) == 0) {
	dev_err(tbn->dev, "AP %s bus ... timeout!\n", msg);
	complete_all(wait_for_completion);
	ret = -ETIMEDOUT;
	} else {
	if (tbn->event_resp.err == 0) {
	dev_info(tbn->dev, "AP %s bus ... SUCCESS!\n", msg);
	} else {
	dev_info(tbn->dev, "AP %s bus ... failed!\n", msg);
	ret = -EBUSY;
	}
	}
	#endif
	} else if (tbn->mode == TBN_MODE_MOCK) {
	dev_info(tbn->dev, "AP %s bus ... SUCCESS!\n", msg);
	} else {
	ret = -EINVAL;
	}

	return ret;
	}

	int tbn_request_bus_with_result(u32 dev_mask, bool *lptw_triggered)
	{
	int ret = 0;

	if (!tbn_context)
	return -ENODEV;

	mutex_lock(&tbn_context->dev_mask_mutex);

	if ((dev_mask & tbn_context->registered_mask) == 0) {
	mutex_unlock(&tbn_context->dev_mask_mutex);
	dev_err(tbn_context->dev, "%s: dev_mask %#x is invalid.\n",
	__func__, dev_mask);
	return -EINVAL;
	}

	if (tbn_context->requested_dev_mask == 0) {
	ret = tbn_handshaking(tbn_context, TBN_OPERATION_AP_REQUEST_BUS);
	if ((ret == 0) && (lptw_triggered != NULL))
	*lptw_triggered = tbn_context->event_resp.lptw_triggered;
	} else {
	dev_dbg(tbn_context->dev,
	"%s: Bus already requested, requested_dev_mask %#x dev_mask %#x.\n",
	__func__, tbn_context->requested_dev_mask, dev_mask);
	}
	tbn_context->requested_dev_mask \|= dev_mask;

	mutex_unlock(&tbn_context->dev_mask_mutex);

	return ret;
	}
	EXPORT_SYMBOL_GPL(tbn_request_bus_with_result);

	int tbn_request_bus(u32 dev_mask)
	{
	return tbn_request_bus_with_result(dev_mask, NULL);
	}
	EXPORT_SYMBOL_GPL(tbn_request_bus);

	int tbn_release_bus(u32 dev_mask)
	{
	int ret = 0;

	if (!tbn_context)
	return -ENODEV;

	mutex_lock(&tbn_context->dev_mask_mutex);

	if ((dev_mask & tbn_context->registered_mask) == 0) {
	mutex_unlock(&tbn_context->dev_mask_mutex);
	dev_err(tbn_context->dev, "%s: dev_mask %#x is invalid.\n",
	__func__, dev_mask);
	return -EINVAL;
	}

	if (tbn_context->requested_dev_mask == 0) {
	dev_warn(tbn_context->dev,
	"%s: Bus already released, dev_mask %#x.\n",
	__func__, dev_mask);
	mutex_unlock(&tbn_context->dev_mask_mutex);
	return 0;
	}

	/* Release the bus when the last requested_dev_mask bit releases. */
	if (tbn_context->requested_dev_mask == dev_mask) {
	ret = tbn_handshaking(tbn_context, TBN_OPERATION_AP_RELEASE_BUS);
	} else {
	dev_dbg(tbn_context->dev,
	"%s: Bus is still in use, requested_dev_mask %#x dev_mask %#x.\n",
	__func__, tbn_context->requested_dev_mask, dev_mask);
	}

	tbn_context->requested_dev_mask &= ~dev_mask;

	mutex_unlock(&tbn_context->dev_mask_mutex);

	return ret;
	}
	EXPORT_SYMBOL_GPL(tbn_release_bus);

	int register_tbn(u32 *output)
	{
	u32 i = 0;

	*output = 0;

	if (!tbn_context) {
	pr_warn("%s: tbn_context doesn't exist.", __func__);
	return 0;
	}

	mutex_lock(&tbn_context->dev_mask_mutex);
	for (i = 0; i < tbn_context->max_devices; i++) {
	if (tbn_context->registered_mask & BIT_MASK(i))
	continue;
	tbn_context->registered_mask \|= BIT_MASK(i);
	/* Assume screen is on while registering tbn. */
	tbn_context->requested_dev_mask \|= BIT_MASK(i);
	*output = BIT_MASK(i);
	break;
	}

	mutex_unlock(&tbn_context->dev_mask_mutex);

	return 0;
	}
	EXPORT_SYMBOL_GPL(register_tbn);

	void unregister_tbn(u32 *output)
	{
	if (!tbn_context)
	return ;

	mutex_lock(&tbn_context->dev_mask_mutex);
	tbn_context->registered_mask &= ~(*output);
	*output = 0;
	mutex_unlock(&tbn_context->dev_mask_mutex);
	}
	EXPORT_SYMBOL_GPL(unregister_tbn);

	static int tbn_probe(struct platform_device *pdev)
	{
	struct device *dev = &pdev->dev;
	struct tbn_context *tbn = NULL;
	struct device_node *np = dev->of_node;
	int err = 0;
	#if IS_ENABLED(CONFIG_TOUCHSCREEN_TBN_AOC_CHANNEL_MODE)
	struct sched_param param = {
	.sched_priority = 10,
	};
	#endif


	tbn = devm_kzalloc(dev, sizeof(struct tbn_context), GFP_KERNEL);
	if (!tbn)
	goto failed;

	tbn->dev = dev;
	tbn->event_resp.lptw_triggered = false;
	tbn_context = tbn;
	dev_set_drvdata(tbn->dev, tbn);

	if (of_property_read_u32(np, "tbn,max_devices", &tbn->max_devices))
	tbn->max_devices = 1;

	err = of_property_read_u32(np, "tbn,mode", &tbn->mode);
	if (err)
	tbn->mode = TBN_MODE_GPIO;

	if (tbn->mode == TBN_MODE_GPIO) {
	tbn->ap2aoc_gpio = of_get_named_gpio(np, "tbn,ap2aoc_gpio", 0);
	if (gpio_is_valid(tbn->ap2aoc_gpio)) {
	err = devm_gpio_request_one(tbn->dev, tbn->ap2aoc_gpio,
	GPIOF_OUT_INIT_LOW, "tbn,ap2aoc_gpio");
	if (err) {
	dev_err(tbn->dev, "%s: Unable to request ap2aoc_gpio %d, err %d!\n",
	__func__, tbn->ap2aoc_gpio, err);
	goto failed;
	}
	} else {
	dev_err(tbn->dev, "%s: invalid ap2aoc_gpio %d!\n",
	__func__, tbn->ap2aoc_gpio);
	err = -EPROBE_DEFER;
	goto failed;
	}

	tbn->aoc2ap_gpio = of_get_named_gpio(np, "tbn,aoc2ap_gpio", 0);
	if (gpio_is_valid(tbn->aoc2ap_gpio)) {
	err = devm_gpio_request_one(tbn->dev, tbn->aoc2ap_gpio,
	GPIOF_DIR_IN, "tbn,aoc2ap_gpio");
	if (err) {
	dev_err(tbn->dev, "%s: Unable to request aoc2ap_gpio %d, err %d!\n",
	__func__, tbn->aoc2ap_gpio, err);
	goto failed;
	}
	tbn->aoc2ap_irq = gpio_to_irq(tbn->aoc2ap_gpio);
	err = devm_request_threaded_irq(tbn->dev,
	tbn->aoc2ap_irq, NULL,
	tbn_aoc2ap_irq_thread,
	IRQF_TRIGGER_RISING \|
	IRQF_ONESHOT, "tbn", tbn);
	if (err) {
	dev_err(tbn->dev,
	"%s: Unable to request_threaded_irq, err %d!\n",
	__func__, err);
	goto failed;
	}
	disable_irq_nosync(tbn->aoc2ap_irq);
	} else {
	dev_err(tbn->dev, "%s: invalid aoc2ap_gpio %d!\n",
	__func__, tbn->aoc2ap_gpio);
	err = -EPROBE_DEFER;
	goto failed;
	}

	dev_info(tbn->dev,
	"%s: gpios(aoc2ap: %d ap2aoc: %d)\n",
	__func__, tbn->aoc2ap_gpio, tbn->ap2aoc_gpio);
	#if IS_ENABLED(CONFIG_TOUCHSCREEN_TBN_AOC_CHANNEL_MODE)
	} else if (tbn->mode == TBN_MODE_AOC_CHANNEL) {
	mutex_init(&tbn->event_lock);

	tbn->aoc_channel_task = kthread_run(&aoc_channel_kthread, tbn,
	TBN_AOC_CHANNEL_THREAD_NAME);
	if (IS_ERR(tbn->aoc_channel_task)) {
	err = PTR_ERR(tbn->aoc_channel_task);
	goto failed;
	}

	err = sched_setscheduler(tbn->aoc_channel_task, SCHED_FIFO, &param);
	if (err != 0) {
	goto failed;
	}
	#endif
	} else if (tbn->mode == TBN_MODE_MOCK) {
	err = 0;
	} else {
	dev_err(tbn->dev, "bus negotiator: invalid mode: %d\n", tbn->mode);
	err = -EINVAL;
	goto failed;
	}

	mutex_init(&tbn->dev_mask_mutex);

	init_completion(&tbn->bus_requested);
	init_completion(&tbn->bus_released);
	complete_all(&tbn->bus_requested);
	complete_all(&tbn->bus_released);

	dev_info(tbn->dev, "bus negotiator initialized: %pK, mode: %d\n", tbn, tbn->mode);

	failed:
	if (err) {
	devm_kfree(dev, tbn);
	tbn_context = NULL;
	}

	return err;
	}

	static int tbn_remove(struct platform_device *pdev)
	{
	struct device *dev = &pdev->dev;
	struct tbn_context *tbn = dev_get_drvdata(dev);

	if (tbn->mode == TBN_MODE_GPIO) {
	free_irq(tbn->aoc2ap_irq, tbn);
	if (gpio_is_valid(tbn->aoc2ap_gpio))
	gpio_free(tbn->aoc2ap_gpio);
	if (gpio_is_valid(tbn->aoc2ap_gpio))
	gpio_free(tbn->aoc2ap_gpio);
	#if IS_ENABLED(CONFIG_TOUCHSCREEN_TBN_AOC_CHANNEL_MODE)
	} else if (tbn->mode == TBN_MODE_AOC_CHANNEL) {
	kthread_stop(tbn->aoc_channel_task);
	#endif
	}
	return 0;
	}

	static struct of_device_id tbn_of_match_table[] = {
	{
	.compatible = TBN_MODULE_NAME,
	},
	{},
	};

	static struct platform_driver tbn_driver = {
	.driver = {
	.name = TBN_MODULE_NAME,
	.of_match_table = tbn_of_match_table,
	},
	.probe = tbn_probe,
	.remove = tbn_remove,
	};

	static int __init tbn_init(void)
	{
	return platform_driver_register(&tbn_driver);
	}

	static void __exit tbn_exit(void)
	{
	platform_driver_unregister(&tbn_driver);
	}
	module_init(tbn_init);
	module_exit(tbn_exit);

	MODULE_SOFTDEP("pre: touch_offload");
	MODULE_LICENSE("GPL v2");
	MODULE_DESCRIPTION("Touch Bus Negotiator");
	MODULE_AUTHOR("Google, Inc.");