/*
   *  Copyright (C) 2013 Daniel Tang <tangrs@tangrs.id.au>
   *
   * 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/input/matrix_keypad.h>
  #include <linux/platform_device.h>
  #include <linux/interrupt.h>
  #include <linux/io.h>
  #include <linux/delay.h>
  #include <linux/input.h>
  #include <linux/slab.h>
  #include <linux/clk.h>
  #include <linux/module.h>
  #include <linux/of.h>
  
  #define KEYPAD_SCAN_MODE	0x00
  #define KEYPAD_CNTL		0x04
  #define KEYPAD_INT		0x08
  #define KEYPAD_INTMSK		0x0C
  
  #define KEYPAD_DATA		0x10
  #define KEYPAD_GPIO		0x30
  
  #define KEYPAD_UNKNOWN_INT	0x40
  #define KEYPAD_UNKNOWN_INT_STS	0x44
  
  #define KEYPAD_BITMASK_COLS	11
  #define KEYPAD_BITMASK_ROWS	8
  
  struct nspire_keypad {
  	void __iomem *reg_base;
  	u32 int_mask;
  
  	struct input_dev *input;
  	struct clk *clk;
  
  	struct matrix_keymap_data *keymap;
  	int row_shift;
  
  	/* Maximum delay estimated assuming 33MHz APB */
  	u32 scan_interval;	/* In microseconds (~2000us max) */
  	u32 row_delay;		/* In microseconds (~500us max) */
  
  	u16 state[KEYPAD_BITMASK_ROWS];
  
  	bool active_low;
  };
  
  static irqreturn_t nspire_keypad_irq(int irq, void *dev_id)
  {
  	struct nspire_keypad *keypad = dev_id;
  	struct input_dev *input = keypad->input;
  	unsigned short *keymap = input->keycode;
  	unsigned int code;
  	int row, col;
  	u32 int_sts;
  	u16 state[8];
  	u16 bits, changed;
  
  	int_sts = readl(keypad->reg_base + KEYPAD_INT) & keypad->int_mask;
  	if (!int_sts)
  		return IRQ_NONE;
  
  	memcpy_fromio(state, keypad->reg_base + KEYPAD_DATA, sizeof(state));
  
  	for (row = 0; row < KEYPAD_BITMASK_ROWS; row++) {
  		bits = state[row];
  		if (keypad->active_low)
  			bits = ~bits;
  
  		changed = bits ^ keypad->state[row];
  		if (!changed)
  			continue;
  
  		keypad->state[row] = bits;
  
  		for (col = 0; col < KEYPAD_BITMASK_COLS; col++) {
  			if (!(changed & (1U << col)))
  				continue;
  
  			code = MATRIX_SCAN_CODE(row, col, keypad->row_shift);
  			input_event(input, EV_MSC, MSC_SCAN, code);
  			input_report_key(input, keymap[code],
  					 bits & (1U << col));
  		}
  	}
  
  	input_sync(input);
  
  	writel(0x3, keypad->reg_base + KEYPAD_INT);
  
  	return IRQ_HANDLED;
  }
  
  static int nspire_keypad_chip_init(struct nspire_keypad *keypad)
  {
  	unsigned long val = 0, cycles_per_us, delay_cycles, row_delay_cycles;
  
  	cycles_per_us = (clk_get_rate(keypad->clk) / 1000000);
  	if (cycles_per_us == 0)
  		cycles_per_us = 1;
  
  	delay_cycles = cycles_per_us * keypad->scan_interval;
  	WARN_ON(delay_cycles >= (1 << 16)); /* Overflow */
  	delay_cycles &= 0xffff;
  
  	row_delay_cycles = cycles_per_us * keypad->row_delay;
  	WARN_ON(row_delay_cycles >= (1 << 14)); /* Overflow */
  	row_delay_cycles &= 0x3fff;
  
  	val |= 3 << 0; /* Set scan mode to 3 (continuous scan) */
  	val |= row_delay_cycles << 2; /* Delay between scanning each row */
  	val |= delay_cycles << 16; /* Delay between scans */
  	writel(val, keypad->reg_base + KEYPAD_SCAN_MODE);
  
  	val = (KEYPAD_BITMASK_ROWS & 0xff) | (KEYPAD_BITMASK_COLS & 0xff)<<8;
  	writel(val, keypad->reg_base + KEYPAD_CNTL);
  
  	/* Enable interrupts */
  	keypad->int_mask = 1 << 1;
  	writel(keypad->int_mask, keypad->reg_base + KEYPAD_INTMSK);
  
  	/* Disable GPIO interrupts to prevent hanging on touchpad */
  	/* Possibly used to detect touchpad events */
  	writel(0, keypad->reg_base + KEYPAD_UNKNOWN_INT);
  	/* Acknowledge existing interrupts */
  	writel(~0, keypad->reg_base + KEYPAD_UNKNOWN_INT_STS);
  
  	return 0;
  }
  
  static int nspire_keypad_open(struct input_dev *input)
  {
  	struct nspire_keypad *keypad = input_get_drvdata(input);
  	int error;
  
  	error = clk_prepare_enable(keypad->clk);
  	if (error)
  		return error;
  
  	error = nspire_keypad_chip_init(keypad);
  	if (error) {
  		clk_disable_unprepare(keypad->clk);
  		return error;
  	}
  
  	return 0;
  }
  
  static void nspire_keypad_close(struct input_dev *input)
  {
  	struct nspire_keypad *keypad = input_get_drvdata(input);
  
  	clk_disable_unprepare(keypad->clk);
  }
  
  static int nspire_keypad_probe(struct platform_device *pdev)
  {
  	const struct device_node *of_node = pdev->dev.of_node;
  	struct nspire_keypad *keypad;
  	struct input_dev *input;
  	struct resource *res;
  	int irq;
  	int error;
  
  	irq = platform_get_irq(pdev, 0);
  	if (irq < 0) {
  		dev_err(&pdev->dev, "failed to get keypad irq
  ");
  		return -EINVAL;
  	}
  
  	keypad = devm_kzalloc(&pdev->dev, sizeof(struct nspire_keypad),
  			      GFP_KERNEL);
  	if (!keypad) {
  		dev_err(&pdev->dev, "failed to allocate keypad memory
  ");
  		return -ENOMEM;
  	}
  
  	keypad->row_shift = get_count_order(KEYPAD_BITMASK_COLS);
  
  	error = of_property_read_u32(of_node, "scan-interval",
  				     &keypad->scan_interval);
  	if (error) {
  		dev_err(&pdev->dev, "failed to get scan-interval
  ");
  		return error;
  	}
  
  	error = of_property_read_u32(of_node, "row-delay",
  				     &keypad->row_delay);
  	if (error) {
  		dev_err(&pdev->dev, "failed to get row-delay
  ");
  		return error;
  	}
  
  	keypad->active_low = of_property_read_bool(of_node, "active-low");
  
  	keypad->clk = devm_clk_get(&pdev->dev, NULL);
  	if (IS_ERR(keypad->clk)) {
  		dev_err(&pdev->dev, "unable to get clock
  ");
  		return PTR_ERR(keypad->clk);
  	}
  
  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	keypad->reg_base = devm_ioremap_resource(&pdev->dev, res);
  	if (IS_ERR(keypad->reg_base))
  		return PTR_ERR(keypad->reg_base);
  
  	keypad->input = input = devm_input_allocate_device(&pdev->dev);
  	if (!input) {
  		dev_err(&pdev->dev, "failed to allocate input device
  ");
  		return -ENOMEM;
  	}
  
  	input_set_drvdata(input, keypad);
  
  	input->id.bustype = BUS_HOST;
  	input->name = "nspire-keypad";
  	input->open = nspire_keypad_open;
  	input->close = nspire_keypad_close;
  
  	__set_bit(EV_KEY, input->evbit);
  	__set_bit(EV_REP, input->evbit);
  	input_set_capability(input, EV_MSC, MSC_SCAN);
  
  	error = matrix_keypad_build_keymap(NULL, NULL,
  					   KEYPAD_BITMASK_ROWS,
  					   KEYPAD_BITMASK_COLS,
  					   NULL, input);
  	if (error) {
  		dev_err(&pdev->dev, "building keymap failed
  ");
  		return error;
  	}
  
  	error = devm_request_irq(&pdev->dev, irq, nspire_keypad_irq, 0,
  				 "nspire_keypad", keypad);
  	if (error) {
  		dev_err(&pdev->dev, "allocate irq %d failed
  ", irq);
  		return error;
  	}
  
  	error = input_register_device(input);
  	if (error) {
  		dev_err(&pdev->dev,
  			"unable to register input device: %d
  ", error);
  		return error;
  	}
  
  	platform_set_drvdata(pdev, keypad);
  
  	dev_dbg(&pdev->dev,
  		"TI-NSPIRE keypad at %pR (scan_interval=%uus, row_delay=%uus%s)
  ",
  		res, keypad->row_delay, keypad->scan_interval,
  		keypad->active_low ? ", active_low" : "");
  
  	return 0;
  }
  
  static const struct of_device_id nspire_keypad_dt_match[] = {
  	{ .compatible = "ti,nspire-keypad" },
  	{ },
  };
  MODULE_DEVICE_TABLE(of, nspire_keypad_dt_match);
  
  static struct platform_driver nspire_keypad_driver = {
  	.driver = {
  		.name = "nspire-keypad",
  		.of_match_table = nspire_keypad_dt_match,
  	},
  	.probe = nspire_keypad_probe,
  };
  
  module_platform_driver(nspire_keypad_driver);
  
  MODULE_LICENSE("GPL");
  MODULE_DESCRIPTION("TI-NSPIRE Keypad Driver");