/*
   * Allwinner sun4i low res adc attached tablet keys driver
   *
   * Copyright (C) 2014 Hans de Goede <hdegoede@redhat.com>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   */
  
  /*
   * Allwinnner sunxi SoCs have a lradc which is specifically designed to have
   * various (tablet) keys (ie home, back, search, etc). attached to it using
   * a resistor network. This driver is for the keys on such boards.
   *
   * There are 2 channels, currently this driver only supports channel 0 since
   * there are no boards known to use channel 1.
   */
  
  #include <linux/err.h>
  #include <linux/init.h>
  #include <linux/input.h>
  #include <linux/interrupt.h>
  #include <linux/io.h>
  #include <linux/module.h>
  #include <linux/of_platform.h>
  #include <linux/platform_device.h>
  #include <linux/regulator/consumer.h>
  #include <linux/slab.h>
  
  #define LRADC_CTRL		0x00
  #define LRADC_INTC		0x04
  #define LRADC_INTS		0x08
  #define LRADC_DATA0		0x0c
  #define LRADC_DATA1		0x10
  
  /* LRADC_CTRL bits */
  #define FIRST_CONVERT_DLY(x)	((x) << 24) /* 8 bits */
  #define CHAN_SELECT(x)		((x) << 22) /* 2 bits */
  #define CONTINUE_TIME_SEL(x)	((x) << 16) /* 4 bits */
  #define KEY_MODE_SEL(x)		((x) << 12) /* 2 bits */
  #define LEVELA_B_CNT(x)		((x) << 8)  /* 4 bits */
  #define HOLD_EN(x)		((x) << 6)
  #define LEVELB_VOL(x)		((x) << 4)  /* 2 bits */
  #define SAMPLE_RATE(x)		((x) << 2)  /* 2 bits */
  #define ENABLE(x)		((x) << 0)
  
  /* LRADC_INTC and LRADC_INTS bits */
  #define CHAN1_KEYUP_IRQ		BIT(12)
  #define CHAN1_ALRDY_HOLD_IRQ	BIT(11)
  #define CHAN1_HOLD_IRQ		BIT(10)
  #define	CHAN1_KEYDOWN_IRQ	BIT(9)
  #define CHAN1_DATA_IRQ		BIT(8)
  #define CHAN0_KEYUP_IRQ		BIT(4)
  #define CHAN0_ALRDY_HOLD_IRQ	BIT(3)
  #define CHAN0_HOLD_IRQ		BIT(2)
  #define	CHAN0_KEYDOWN_IRQ	BIT(1)
  #define CHAN0_DATA_IRQ		BIT(0)
  
  struct sun4i_lradc_keymap {
  	u32 voltage;
  	u32 keycode;
  };
  
  struct sun4i_lradc_data {
  	struct device *dev;
  	struct input_dev *input;
  	void __iomem *base;
  	struct regulator *vref_supply;
  	struct sun4i_lradc_keymap *chan0_map;
  	u32 chan0_map_count;
  	u32 chan0_keycode;
  	u32 vref;
  };
  
  static irqreturn_t sun4i_lradc_irq(int irq, void *dev_id)
  {
  	struct sun4i_lradc_data *lradc = dev_id;
  	u32 i, ints, val, voltage, diff, keycode = 0, closest = 0xffffffff;
  
  	ints  = readl(lradc->base + LRADC_INTS);
  
  	/*
  	 * lradc supports only one keypress at a time, release does not give
  	 * any info as to which key was released, so we cache the keycode.
  	 */
  
  	if (ints & CHAN0_KEYUP_IRQ) {
  		input_report_key(lradc->input, lradc->chan0_keycode, 0);
  		lradc->chan0_keycode = 0;
  	}
  
  	if ((ints & CHAN0_KEYDOWN_IRQ) && lradc->chan0_keycode == 0) {
  		val = readl(lradc->base + LRADC_DATA0) & 0x3f;
  		voltage = val * lradc->vref / 63;
  
  		for (i = 0; i < lradc->chan0_map_count; i++) {
  			diff = abs(lradc->chan0_map[i].voltage - voltage);
  			if (diff < closest) {
  				closest = diff;
  				keycode = lradc->chan0_map[i].keycode;
  			}
  		}
  
  		lradc->chan0_keycode = keycode;
  		input_report_key(lradc->input, lradc->chan0_keycode, 1);
  	}
  
  	input_sync(lradc->input);
  
  	writel(ints, lradc->base + LRADC_INTS);
  
  	return IRQ_HANDLED;
  }
  
  static int sun4i_lradc_open(struct input_dev *dev)
  {
  	struct sun4i_lradc_data *lradc = input_get_drvdata(dev);
  	int error;
  
  	error = regulator_enable(lradc->vref_supply);
  	if (error)
  		return error;
  
  	/* lradc Vref internally is divided by 2/3 */
  	lradc->vref = regulator_get_voltage(lradc->vref_supply) * 2 / 3;
  
  	/*
  	 * Set sample time to 4 ms / 250 Hz. Wait 2 * 4 ms for key to
  	 * stabilize on press, wait (1 + 1) * 4 ms for key release
  	 */
  	writel(FIRST_CONVERT_DLY(2) | LEVELA_B_CNT(1) | HOLD_EN(1) |
  		SAMPLE_RATE(0) | ENABLE(1), lradc->base + LRADC_CTRL);
  
  	writel(CHAN0_KEYUP_IRQ | CHAN0_KEYDOWN_IRQ, lradc->base + LRADC_INTC);
  
  	return 0;
  }
  
  static void sun4i_lradc_close(struct input_dev *dev)
  {
  	struct sun4i_lradc_data *lradc = input_get_drvdata(dev);
  
  	/* Disable lradc, leave other settings unchanged */
  	writel(FIRST_CONVERT_DLY(2) | LEVELA_B_CNT(1) | HOLD_EN(1) |
  		SAMPLE_RATE(2), lradc->base + LRADC_CTRL);
  	writel(0, lradc->base + LRADC_INTC);
  
  	regulator_disable(lradc->vref_supply);
  }
  
  static int sun4i_lradc_load_dt_keymap(struct device *dev,
  				      struct sun4i_lradc_data *lradc)
  {
  	struct device_node *np, *pp;
  	int i;
  	int error;
  
  	np = dev->of_node;
  	if (!np)
  		return -EINVAL;
  
  	lradc->chan0_map_count = of_get_child_count(np);
  	if (lradc->chan0_map_count == 0) {
  		dev_err(dev, "keymap is missing in device tree
  ");
  		return -EINVAL;
  	}
  
  	lradc->chan0_map = devm_kmalloc_array(dev, lradc->chan0_map_count,
  					      sizeof(struct sun4i_lradc_keymap),
  					      GFP_KERNEL);
  	if (!lradc->chan0_map)
  		return -ENOMEM;
  
  	i = 0;
  	for_each_child_of_node(np, pp) {
  		struct sun4i_lradc_keymap *map = &lradc->chan0_map[i];
  		u32 channel;
  
  		error = of_property_read_u32(pp, "channel", &channel);
  		if (error || channel != 0) {
  			dev_err(dev, "%s: Inval channel prop
  ", pp->name);
  			return -EINVAL;
  		}
  
  		error = of_property_read_u32(pp, "voltage", &map->voltage);
  		if (error) {
  			dev_err(dev, "%s: Inval voltage prop
  ", pp->name);
  			return -EINVAL;
  		}
  
  		error = of_property_read_u32(pp, "linux,code", &map->keycode);
  		if (error) {
  			dev_err(dev, "%s: Inval linux,code prop
  ", pp->name);
  			return -EINVAL;
  		}
  
  		i++;
  	}
  
  	return 0;
  }
  
  static int sun4i_lradc_probe(struct platform_device *pdev)
  {
  	struct sun4i_lradc_data *lradc;
  	struct device *dev = &pdev->dev;
  	int i;
  	int error;
  
  	lradc = devm_kzalloc(dev, sizeof(struct sun4i_lradc_data), GFP_KERNEL);
  	if (!lradc)
  		return -ENOMEM;
  
  	error = sun4i_lradc_load_dt_keymap(dev, lradc);
  	if (error)
  		return error;
  
  	lradc->vref_supply = devm_regulator_get(dev, "vref");
  	if (IS_ERR(lradc->vref_supply))
  		return PTR_ERR(lradc->vref_supply);
  
  	lradc->dev = dev;
  	lradc->input = devm_input_allocate_device(dev);
  	if (!lradc->input)
  		return -ENOMEM;
  
  	lradc->input->name = pdev->name;
  	lradc->input->phys = "sun4i_lradc/input0";
  	lradc->input->open = sun4i_lradc_open;
  	lradc->input->close = sun4i_lradc_close;
  	lradc->input->id.bustype = BUS_HOST;
  	lradc->input->id.vendor = 0x0001;
  	lradc->input->id.product = 0x0001;
  	lradc->input->id.version = 0x0100;
  
  	__set_bit(EV_KEY, lradc->input->evbit);
  	for (i = 0; i < lradc->chan0_map_count; i++)
  		__set_bit(lradc->chan0_map[i].keycode, lradc->input->keybit);
  
  	input_set_drvdata(lradc->input, lradc);
  
  	lradc->base = devm_ioremap_resource(dev,
  			      platform_get_resource(pdev, IORESOURCE_MEM, 0));
  	if (IS_ERR(lradc->base))
  		return PTR_ERR(lradc->base);
  
  	error = devm_request_irq(dev, platform_get_irq(pdev, 0),
  				 sun4i_lradc_irq, 0,
  				 "sun4i-a10-lradc-keys", lradc);
  	if (error)
  		return error;
  
  	error = input_register_device(lradc->input);
  	if (error)
  		return error;
  
  	platform_set_drvdata(pdev, lradc);
  	return 0;
  }
  
  static const struct of_device_id sun4i_lradc_of_match[] = {
  	{ .compatible = "allwinner,sun4i-a10-lradc-keys", },
  	{ /* sentinel */ }
  };
  MODULE_DEVICE_TABLE(of, sun4i_lradc_of_match);
  
  static struct platform_driver sun4i_lradc_driver = {
  	.driver = {
  		.name	= "sun4i-a10-lradc-keys",
  		.of_match_table = of_match_ptr(sun4i_lradc_of_match),
  	},
  	.probe	= sun4i_lradc_probe,
  };
  
  module_platform_driver(sun4i_lradc_driver);
  
  MODULE_DESCRIPTION("Allwinner sun4i low res adc attached tablet keys driver");
  MODULE_AUTHOR("Hans de Goede <hdegoede@redhat.com>");
  MODULE_LICENSE("GPL");