/*
 * Driver for the IMX keypad port.
 * Copyright (C) 2009 Alberto Panizzo <maramaopercheseimorto@gmail.com>
 *
 * 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.
 *
 * <<Power management needs to be implemented>>.
 */

#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/input/matrix_keypad.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/jiffies.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/timer.h>

/*
 * Keypad Controller registers (halfword)
 */
#define KPCR		0x00 /* Keypad Control Register */

#define KPSR		0x02 /* Keypad Status Register */
#define KBD_STAT_KPKD	(0x1 << 0) /* Key Press Interrupt Status bit (w1c) */
#define KBD_STAT_KPKR	(0x1 << 1) /* Key Release Interrupt Status bit (w1c) */
#define KBD_STAT_KDSC	(0x1 << 2) /* Key Depress Synch Chain Status bit (w1c)*/
#define KBD_STAT_KRSS	(0x1 << 3) /* Key Release Synch Status bit (w1c)*/
#define KBD_STAT_KDIE	(0x1 << 8) /* Key Depress Interrupt Enable Status bit */
#define KBD_STAT_KRIE	(0x1 << 9) /* Key Release Interrupt Enable */
#define KBD_STAT_KPPEN	(0x1 << 10) /* Keypad Clock Enable */

#define KDDR		0x04 /* Keypad Data Direction Register */
#define KPDR		0x06 /* Keypad Data Register */

#define MAX_MATRIX_KEY_ROWS	8
#define MAX_MATRIX_KEY_COLS	8
#define MATRIX_ROW_SHIFT	3

#define MAX_MATRIX_KEY_NUM	(MAX_MATRIX_KEY_ROWS * MAX_MATRIX_KEY_COLS)

struct imx_keypad {

	struct clk *clk;
	struct input_dev *input_dev;
	void __iomem *mmio_base;

	int			irq;
	struct timer_list	check_matrix_timer;

	/*
	 * The matrix is stable only if no changes are detected after
	 * IMX_KEYPAD_SCANS_FOR_STABILITY scans
	 */
#define IMX_KEYPAD_SCANS_FOR_STABILITY 3
	int			stable_count;

	bool			enabled;

	/* Masks for enabled rows/cols */
	unsigned short		rows_en_mask;
	unsigned short		cols_en_mask;

	unsigned short		keycodes[MAX_MATRIX_KEY_NUM];

	/*
	 * Matrix states:
	 * -stable: achieved after a complete debounce process.
	 * -unstable: used in the debouncing process.
	 */
	unsigned short		matrix_stable_state[MAX_MATRIX_KEY_COLS];
	unsigned short		matrix_unstable_state[MAX_MATRIX_KEY_COLS];
};

/* Scan the matrix and return the new state in *matrix_volatile_state. */
static void imx_keypad_scan_matrix(struct imx_keypad *keypad,
				  unsigned short *matrix_volatile_state)
{
	int col;
	unsigned short reg_val;

	for (col = 0; col < MAX_MATRIX_KEY_COLS; col++) {
		if ((keypad->cols_en_mask & (1 << col)) == 0)
			continue;
		/*
		 * Discharge keypad capacitance:
		 * 2. write 1s on column data.
		 * 3. configure columns as totem-pole to discharge capacitance.
		 * 4. configure columns as open-drain.
		 */
		reg_val = readw(keypad->mmio_base + KPDR);
		reg_val |= 0xff00;
		writew(reg_val, keypad->mmio_base + KPDR);

		reg_val = readw(keypad->mmio_base + KPCR);
		reg_val &= ~((keypad->cols_en_mask & 0xff) << 8);
		writew(reg_val, keypad->mmio_base + KPCR);

		udelay(2);

		reg_val = readw(keypad->mmio_base + KPCR);
		reg_val |= (keypad->cols_en_mask & 0xff) << 8;
		writew(reg_val, keypad->mmio_base + KPCR);

		/*
		 * 5. Write a single column to 0, others to 1.
		 * 6. Sample row inputs and save data.
		 * 7. Repeat steps 2 - 6 for remaining columns.
		 */
		reg_val = readw(keypad->mmio_base + KPDR);
		reg_val &= ~(1 << (8 + col));
		writew(reg_val, keypad->mmio_base + KPDR);

		/*
		 * Delay added to avoid propagating the 0 from column to row
		 * when scanning.
		 */
		udelay(5);

		/*
		 * 1s in matrix_volatile_state[col] means key pressures
		 * throw data from non enabled rows.
		 */
		reg_val = readw(keypad->mmio_base + KPDR);
		matrix_volatile_state[col] = (~reg_val) & keypad->rows_en_mask;
	}

	/*
	 * Return in standby mode:
	 * 9. write 0s to columns
	 */
	reg_val = readw(keypad->mmio_base + KPDR);
	reg_val &= 0x00ff;
	writew(reg_val, keypad->mmio_base + KPDR);
}

/*
 * Compare the new matrix state (volatile) with the stable one stored in
 * keypad->matrix_stable_state and fire events if changes are detected.
 */
static void imx_keypad_fire_events(struct imx_keypad *keypad,
				   unsigned short *matrix_volatile_state)
{
	struct input_dev *input_dev = keypad->input_dev;
	int row, col;

	for (col = 0; col < MAX_MATRIX_KEY_COLS; col++) {
		unsigned short bits_changed;
		int code;

		if ((keypad->cols_en_mask & (1 << col)) == 0)
			continue; /* Column is not enabled */

		bits_changed = keypad->matrix_stable_state[col] ^
						matrix_volatile_state[col];

		if (bits_changed == 0)
			continue; /* Column does not contain changes */

		for (row = 0; row < MAX_MATRIX_KEY_ROWS; row++) {
			if ((keypad->rows_en_mask & (1 << row)) == 0)
				continue; /* Row is not enabled */
			if ((bits_changed & (1 << row)) == 0)
				continue; /* Row does not contain changes */

			code = MATRIX_SCAN_CODE(row, col, MATRIX_ROW_SHIFT);
			input_event(input_dev, EV_MSC, MSC_SCAN, code);
			input_report_key(input_dev, keypad->keycodes[code],
				matrix_volatile_state[col] & (1 << row));
			dev_dbg(&input_dev->dev, "Event code: %d, val: %d",
				keypad->keycodes[code],
				matrix_volatile_state[col] & (1 << row));
		}
	}
	input_sync(input_dev);
}

/*
 * imx_keypad_check_for_events is the timer handler.
 */
static void imx_keypad_check_for_events(unsigned long data)
{
	struct imx_keypad *keypad = (struct imx_keypad *) data;
	unsigned short matrix_volatile_state[MAX_MATRIX_KEY_COLS];
	unsigned short reg_val;
	bool state_changed, is_zero_matrix;
	int i;

	memset(matrix_volatile_state, 0, sizeof(matrix_volatile_state));

	imx_keypad_scan_matrix(keypad, matrix_volatile_state);

	state_changed = false;
	for (i = 0; i < MAX_MATRIX_KEY_COLS; i++) {
		if ((keypad->cols_en_mask & (1 << i)) == 0)
			continue;

		if (keypad->matrix_unstable_state[i] ^ matrix_volatile_state[i]) {
			state_changed = true;
			break;
		}
	}

	/*
	 * If the matrix state is changed from the previous scan
	 *   (Re)Begin the debouncing process, saving the new state in
	 *    keypad->matrix_unstable_state.
	 * else
	 *   Increase the count of number of scans with a stable state.
	 */
	if (state_changed) {
		memcpy(keypad->matrix_unstable_state, matrix_volatile_state,
			sizeof(matrix_volatile_state));
		keypad->stable_count = 0;
	} else
		keypad->stable_count++;

	/*
	 * If the matrix is not as stable as we want reschedule scan
	 * in the near future.
	 */
	if (keypad->stable_count < IMX_KEYPAD_SCANS_FOR_STABILITY) {
		mod_timer(&keypad->check_matrix_timer,
			  jiffies + msecs_to_jiffies(10));
		return;
	}

	/*
	 * If the matrix state is stable, fire the events and save the new
	 * stable state. Note, if the matrix is kept stable for longer
	 * (keypad->stable_count > IMX_KEYPAD_SCANS_FOR_STABILITY) all
	 * events have already been generated.
	 */
	if (keypad->stable_count == IMX_KEYPAD_SCANS_FOR_STABILITY) {
		imx_keypad_fire_events(keypad, matrix_volatile_state);

		memcpy(keypad->matrix_stable_state, matrix_volatile_state,
			sizeof(matrix_volatile_state));
	}

	is_zero_matrix = true;
	for (i = 0; i < MAX_MATRIX_KEY_COLS; i++) {
		if (matrix_volatile_state[i] != 0) {
			is_zero_matrix = false;
			break;
		}
	}


	if (is_zero_matrix) {
		/*
		 * All keys have been released. Enable only the KDI
		 * interrupt for future key presses (clear the KDI
		 * status bit and its sync chain before that).
		 */
		reg_val = readw(keypad->mmio_base + KPSR);
		reg_val |= KBD_STAT_KPKD | KBD_STAT_KDSC;
		writew(reg_val, keypad->mmio_base + KPSR);

		reg_val = readw(keypad->mmio_base + KPSR);
		reg_val |= KBD_STAT_KDIE;
		reg_val &= ~KBD_STAT_KRIE;
		writew(reg_val, keypad->mmio_base + KPSR);
	} else {
		/*
		 * Some keys are still pressed. Schedule a rescan in
		 * attempt to detect multiple key presses and enable
		 * the KRI interrupt to react quickly to key release
		 * event.
		 */
		mod_timer(&keypad->check_matrix_timer,
			  jiffies + msecs_to_jiffies(60));

		reg_val = readw(keypad->mmio_base + KPSR);
		reg_val |= KBD_STAT_KPKR | KBD_STAT_KRSS;
		writew(reg_val, keypad->mmio_base + KPSR);

		reg_val = readw(keypad->mmio_base + KPSR);
		reg_val |= KBD_STAT_KRIE;
		reg_val &= ~KBD_STAT_KDIE;
		writew(reg_val, keypad->mmio_base + KPSR);
	}
}

static irqreturn_t imx_keypad_irq_handler(int irq, void *dev_id)
{
	struct imx_keypad *keypad = dev_id;
	unsigned short reg_val;

	reg_val = readw(keypad->mmio_base + KPSR);

	/* Disable both interrupt types */
	reg_val &= ~(KBD_STAT_KRIE | KBD_STAT_KDIE);
	/* Clear interrupts status bits */
	reg_val |= KBD_STAT_KPKR | KBD_STAT_KPKD;
	writew(reg_val, keypad->mmio_base + KPSR);

	if (keypad->enabled) {
		/* The matrix is supposed to be changed */
		keypad->stable_count = 0;

		/* Schedule the scanning procedure near in the future */
		mod_timer(&keypad->check_matrix_timer,
			  jiffies + msecs_to_jiffies(2));
	}

	return IRQ_HANDLED;
}

static void imx_keypad_config(struct imx_keypad *keypad)
{
	unsigned short reg_val;

	/*
	 * Include enabled rows in interrupt generation (KPCR[7:0])
	 * Configure keypad columns as open-drain (KPCR[15:8])
	 */
	reg_val = readw(keypad->mmio_base + KPCR);
	reg_val |= keypad->rows_en_mask & 0xff;		/* rows */
	reg_val |= (keypad->cols_en_mask & 0xff) << 8;	/* cols */
	writew(reg_val, keypad->mmio_base + KPCR);

	/* Write 0's to KPDR[15:8] (Colums) */
	reg_val = readw(keypad->mmio_base + KPDR);
	reg_val &= 0x00ff;
	writew(reg_val, keypad->mmio_base + KPDR);

	/* Configure columns as output, rows as input (KDDR[15:0]) */
	writew(0xff00, keypad->mmio_base + KDDR);

	/*
	 * Clear Key Depress and Key Release status bit.
	 * Clear both synchronizer chain.
	 */
	reg_val = readw(keypad->mmio_base + KPSR);
	reg_val |= KBD_STAT_KPKR | KBD_STAT_KPKD |
		   KBD_STAT_KDSC | KBD_STAT_KRSS;
	writew(reg_val, keypad->mmio_base + KPSR);

	/* Enable KDI and disable KRI (avoid false release events). */
	reg_val |= KBD_STAT_KDIE;
	reg_val &= ~KBD_STAT_KRIE;
	writew(reg_val, keypad->mmio_base + KPSR);
}

static void imx_keypad_inhibit(struct imx_keypad *keypad)
{
	unsigned short reg_val;

	/* Inhibit KDI and KRI interrupts. */
	reg_val = readw(keypad->mmio_base + KPSR);
	reg_val &= ~(KBD_STAT_KRIE | KBD_STAT_KDIE);
	writew(reg_val, keypad->mmio_base + KPSR);

	/* Colums as open drain and disable all rows */
	writew(0xff00, keypad->mmio_base + KPCR);
}

static void imx_keypad_close(struct input_dev *dev)
{
	struct imx_keypad *keypad = input_get_drvdata(dev);

	dev_dbg(&dev->dev, ">%s\n", __func__);

	/* Mark keypad as being inactive */
	keypad->enabled = false;
	synchronize_irq(keypad->irq);
	del_timer_sync(&keypad->check_matrix_timer);

	imx_keypad_inhibit(keypad);

	/* Disable clock unit */
	clk_disable(keypad->clk);
}

static int imx_keypad_open(struct input_dev *dev)
{
	struct imx_keypad *keypad = input_get_drvdata(dev);

	dev_dbg(&dev->dev, ">%s\n", __func__);

	/* We became active from now */
	keypad->enabled = true;

	/* Enable the kpp clock */
	clk_enable(keypad->clk);
	imx_keypad_config(keypad);

	/* Sanity control, not all the rows must be actived now. */
	if ((readw(keypad->mmio_base + KPDR) & keypad->rows_en_mask) == 0) {
		dev_err(&dev->dev,
			"too many keys pressed, control pins initialisation\n");
		goto open_err;
	}

	return 0;

open_err:
	imx_keypad_close(dev);
	return -EIO;
}

static int __devinit imx_keypad_probe(struct platform_device *pdev)
{
	const struct matrix_keymap_data *keymap_data = pdev->dev.platform_data;
	struct imx_keypad *keypad;
	struct input_dev *input_dev;
	struct resource *res;
	int irq, error, i;

	if (keymap_data == NULL) {
		dev_err(&pdev->dev, "no keymap defined\n");
		return -EINVAL;
	}

	irq = platform_get_irq(pdev, 0);
	if (irq < 0) {
		dev_err(&pdev->dev, "no irq defined in platform data\n");
		return -EINVAL;
	}

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (res == NULL) {
		dev_err(&pdev->dev, "no I/O memory defined in platform data\n");
		return -EINVAL;
	}

	res = request_mem_region(res->start, resource_size(res), pdev->name);
	if (res == NULL) {
		dev_err(&pdev->dev, "failed to request I/O memory\n");
		return -EBUSY;
	}

	input_dev = input_allocate_device();
	if (!input_dev) {
		dev_err(&pdev->dev, "failed to allocate the input device\n");
		error = -ENOMEM;
		goto failed_rel_mem;
	}

	keypad = kzalloc(sizeof(struct imx_keypad), GFP_KERNEL);
	if (!keypad) {
		dev_err(&pdev->dev, "not enough memory for driver data\n");
		error = -ENOMEM;
		goto failed_free_input;
	}

	keypad->input_dev = input_dev;
	keypad->irq = irq;
	keypad->stable_count = 0;

	setup_timer(&keypad->check_matrix_timer,
		    imx_keypad_check_for_events, (unsigned long) keypad);

	keypad->mmio_base = ioremap(res->start, resource_size(res));
	if (keypad->mmio_base == NULL) {
		dev_err(&pdev->dev, "failed to remap I/O memory\n");
		error = -ENOMEM;
		goto failed_free_priv;
	}

	keypad->clk = clk_get(&pdev->dev, "kpp");
	if (IS_ERR(keypad->clk)) {
		dev_err(&pdev->dev, "failed to get keypad clock\n");
		error = PTR_ERR(keypad->clk);
		goto failed_unmap;
	}

	/* Search for rows and cols enabled */
	for (i = 0; i < keymap_data->keymap_size; i++) {
		keypad->rows_en_mask |= 1 << KEY_ROW(keymap_data->keymap[i]);
		keypad->cols_en_mask |= 1 << KEY_COL(keymap_data->keymap[i]);
	}

	if (keypad->rows_en_mask > ((1 << MAX_MATRIX_KEY_ROWS) - 1) ||
	   keypad->cols_en_mask > ((1 << MAX_MATRIX_KEY_COLS) - 1)) {
		dev_err(&pdev->dev,
			"invalid key data (too many rows or colums)\n");
		error = -EINVAL;
		goto failed_clock_put;
	}
	dev_dbg(&pdev->dev, "enabled rows mask: %x\n", keypad->rows_en_mask);
	dev_dbg(&pdev->dev, "enabled cols mask: %x\n", keypad->cols_en_mask);

	/* Init the Input device */
	input_dev->name = pdev->name;
	input_dev->id.bustype = BUS_HOST;
	input_dev->dev.parent = &pdev->dev;
	input_dev->open = imx_keypad_open;
	input_dev->close = imx_keypad_close;
	input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_REP);
	input_dev->keycode = keypad->keycodes;
	input_dev->keycodesize = sizeof(keypad->keycodes[0]);
	input_dev->keycodemax = ARRAY_SIZE(keypad->keycodes);

	matrix_keypad_build_keymap(keymap_data, MATRIX_ROW_SHIFT,
				keypad->keycodes, input_dev->keybit);

	input_set_capability(input_dev, EV_MSC, MSC_SCAN);
	input_set_drvdata(input_dev, keypad);

	/* Ensure that the keypad will stay dormant until opened */
	imx_keypad_inhibit(keypad);

	error = request_irq(irq, imx_keypad_irq_handler, IRQF_DISABLED,
			    pdev->name, keypad);
	if (error) {
		dev_err(&pdev->dev, "failed to request IRQ\n");
		goto failed_clock_put;
	}

	/* Register the input device */
	error = input_register_device(input_dev);
	if (error) {
		dev_err(&pdev->dev, "failed to register input device\n");
		goto failed_free_irq;
	}

	platform_set_drvdata(pdev, keypad);
	device_init_wakeup(&pdev->dev, 1);

	return 0;

failed_free_irq:
	free_irq(irq, pdev);
failed_clock_put:
	clk_put(keypad->clk);
failed_unmap:
	iounmap(keypad->mmio_base);
failed_free_priv:
	kfree(keypad);
failed_free_input:
	input_free_device(input_dev);
failed_rel_mem:
	release_mem_region(res->start, resource_size(res));
	return error;
}

static int __devexit imx_keypad_remove(struct platform_device *pdev)
{
	struct imx_keypad *keypad = platform_get_drvdata(pdev);
	struct resource *res;

	dev_dbg(&pdev->dev, ">%s\n", __func__);

	platform_set_drvdata(pdev, NULL);

	input_unregister_device(keypad->input_dev);

	free_irq(keypad->irq, keypad);
	clk_put(keypad->clk);

	iounmap(keypad->mmio_base);
	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	release_mem_region(res->start, resource_size(res));

	kfree(keypad);

	return 0;
}

static struct platform_driver imx_keypad_driver = {
	.driver		= {
		.name	= "imx-keypad",
		.owner	= THIS_MODULE,
	},
	.probe		= imx_keypad_probe,
	.remove		= __devexit_p(imx_keypad_remove),
};

static int __init imx_keypad_init(void)
{
	return platform_driver_register(&imx_keypad_driver);
}

static void __exit imx_keypad_exit(void)
{
	platform_driver_unregister(&imx_keypad_driver);
}

module_init(imx_keypad_init);
module_exit(imx_keypad_exit);

MODULE_AUTHOR("Alberto Panizzo <maramaopercheseimorto@gmail.com>");
MODULE_DESCRIPTION("IMX Keypad Port Driver");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS("platform:imx-keypad");