1/*
  2 * Allwinner sun4i low res adc attached tablet keys driver
  3 *
  4 * Copyright (C) 2014 Hans de Goede <hdegoede@redhat.com>
  5 *
  6 * This program is free software; you can redistribute it and/or modify
  7 * it under the terms of the GNU General Public License as published by
  8 * the Free Software Foundation; either version 2 of the License, or
  9 * (at your option) any later version.
 10 *
 11 * This program is distributed in the hope that it will be useful,
 12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 14 * GNU General Public License for more details.
 15 */
 16
 17/*
 18 * Allwinnner sunxi SoCs have a lradc which is specifically designed to have
 19 * various (tablet) keys (ie home, back, search, etc). attached to it using
 20 * a resistor network. This driver is for the keys on such boards.
 21 *
 22 * There are 2 channels, currently this driver only supports channel 0 since
 23 * there are no boards known to use channel 1.
 24 */
 25
 26#include <linux/err.h>
 27#include <linux/init.h>
 28#include <linux/input.h>
 29#include <linux/interrupt.h>
 30#include <linux/io.h>
 31#include <linux/module.h>
 32#include <linux/of_platform.h>
 33#include <linux/platform_device.h>
 34#include <linux/regulator/consumer.h>
 35#include <linux/slab.h>
 36
 37#define LRADC_CTRL		0x00
 38#define LRADC_INTC		0x04
 39#define LRADC_INTS		0x08
 40#define LRADC_DATA0		0x0c
 41#define LRADC_DATA1		0x10
 42
 43/* LRADC_CTRL bits */
 44#define FIRST_CONVERT_DLY(x)	((x) << 24) /* 8 bits */
 45#define CHAN_SELECT(x)		((x) << 22) /* 2 bits */
 46#define CONTINUE_TIME_SEL(x)	((x) << 16) /* 4 bits */
 47#define KEY_MODE_SEL(x)		((x) << 12) /* 2 bits */
 48#define LEVELA_B_CNT(x)		((x) << 8)  /* 4 bits */
 49#define HOLD_EN(x)		((x) << 6)
 50#define LEVELB_VOL(x)		((x) << 4)  /* 2 bits */
 51#define SAMPLE_RATE(x)		((x) << 2)  /* 2 bits */
 52#define ENABLE(x)		((x) << 0)
 53
 54/* LRADC_INTC and LRADC_INTS bits */
 55#define CHAN1_KEYUP_IRQ		BIT(12)
 56#define CHAN1_ALRDY_HOLD_IRQ	BIT(11)
 57#define CHAN1_HOLD_IRQ		BIT(10)
 58#define	CHAN1_KEYDOWN_IRQ	BIT(9)
 59#define CHAN1_DATA_IRQ		BIT(8)
 60#define CHAN0_KEYUP_IRQ		BIT(4)
 61#define CHAN0_ALRDY_HOLD_IRQ	BIT(3)
 62#define CHAN0_HOLD_IRQ		BIT(2)
 63#define	CHAN0_KEYDOWN_IRQ	BIT(1)
 64#define CHAN0_DATA_IRQ		BIT(0)
 65
 66struct sun4i_lradc_keymap {
 67	u32 voltage;
 68	u32 keycode;
 69};
 70
 71struct sun4i_lradc_data {
 72	struct device *dev;
 73	struct input_dev *input;
 74	void __iomem *base;
 75	struct regulator *vref_supply;
 76	struct sun4i_lradc_keymap *chan0_map;
 77	u32 chan0_map_count;
 78	u32 chan0_keycode;
 79	u32 vref;
 80};
 81
 82static irqreturn_t sun4i_lradc_irq(int irq, void *dev_id)
 83{
 84	struct sun4i_lradc_data *lradc = dev_id;
 85	u32 i, ints, val, voltage, diff, keycode = 0, closest = 0xffffffff;
 86
 87	ints  = readl(lradc->base + LRADC_INTS);
 88
 89	/*
 90	 * lradc supports only one keypress at a time, release does not give
 91	 * any info as to which key was released, so we cache the keycode.
 92	 */
 93
 94	if (ints & CHAN0_KEYUP_IRQ) {
 95		input_report_key(lradc->input, lradc->chan0_keycode, 0);
 96		lradc->chan0_keycode = 0;
 97	}
 98
 99	if ((ints & CHAN0_KEYDOWN_IRQ) && lradc->chan0_keycode == 0) {
100		val = readl(lradc->base + LRADC_DATA0) & 0x3f;
101		voltage = val * lradc->vref / 63;
102
103		for (i = 0; i < lradc->chan0_map_count; i++) {
104			diff = abs(lradc->chan0_map[i].voltage - voltage);
105			if (diff < closest) {
106				closest = diff;
107				keycode = lradc->chan0_map[i].keycode;
108			}
109		}
110
111		lradc->chan0_keycode = keycode;
112		input_report_key(lradc->input, lradc->chan0_keycode, 1);
113	}
114
115	input_sync(lradc->input);
116
117	writel(ints, lradc->base + LRADC_INTS);
118
119	return IRQ_HANDLED;
120}
121
122static int sun4i_lradc_open(struct input_dev *dev)
123{
124	struct sun4i_lradc_data *lradc = input_get_drvdata(dev);
125	int error;
126
127	error = regulator_enable(lradc->vref_supply);
128	if (error)
129		return error;
130
131	/* lradc Vref internally is divided by 2/3 */
132	lradc->vref = regulator_get_voltage(lradc->vref_supply) * 2 / 3;
133
134	/*
135	 * Set sample time to 4 ms / 250 Hz. Wait 2 * 4 ms for key to
136	 * stabilize on press, wait (1 + 1) * 4 ms for key release
137	 */
138	writel(FIRST_CONVERT_DLY(2) | LEVELA_B_CNT(1) | HOLD_EN(1) |
139		SAMPLE_RATE(0) | ENABLE(1), lradc->base + LRADC_CTRL);
140
141	writel(CHAN0_KEYUP_IRQ | CHAN0_KEYDOWN_IRQ, lradc->base + LRADC_INTC);
142
143	return 0;
144}
145
146static void sun4i_lradc_close(struct input_dev *dev)
147{
148	struct sun4i_lradc_data *lradc = input_get_drvdata(dev);
149
150	/* Disable lradc, leave other settings unchanged */
151	writel(FIRST_CONVERT_DLY(2) | LEVELA_B_CNT(1) | HOLD_EN(1) |
152		SAMPLE_RATE(2), lradc->base + LRADC_CTRL);
153	writel(0, lradc->base + LRADC_INTC);
154
155	regulator_disable(lradc->vref_supply);
156}
157
158static int sun4i_lradc_load_dt_keymap(struct device *dev,
159				      struct sun4i_lradc_data *lradc)
160{
161	struct device_node *np, *pp;
162	int i;
163	int error;
164
165	np = dev->of_node;
166	if (!np)
167		return -EINVAL;
168
169	lradc->chan0_map_count = of_get_child_count(np);
170	if (lradc->chan0_map_count == 0) {
171		dev_err(dev, "keymap is missing in device tree\n");
172		return -EINVAL;
173	}
174
175	lradc->chan0_map = devm_kmalloc_array(dev, lradc->chan0_map_count,
176					      sizeof(struct sun4i_lradc_keymap),
177					      GFP_KERNEL);
178	if (!lradc->chan0_map)
179		return -ENOMEM;
180
181	i = 0;
182	for_each_child_of_node(np, pp) {
183		struct sun4i_lradc_keymap *map = &lradc->chan0_map[i];
184		u32 channel;
185
186		error = of_property_read_u32(pp, "channel", &channel);
187		if (error || channel != 0) {
188			dev_err(dev, "%s: Inval channel prop\n", pp->name);
189			return -EINVAL;
190		}
191
192		error = of_property_read_u32(pp, "voltage", &map->voltage);
193		if (error) {
194			dev_err(dev, "%s: Inval voltage prop\n", pp->name);
195			return -EINVAL;
196		}
197
198		error = of_property_read_u32(pp, "linux,code", &map->keycode);
199		if (error) {
200			dev_err(dev, "%s: Inval linux,code prop\n", pp->name);
201			return -EINVAL;
202		}
203
204		i++;
205	}
206
207	return 0;
208}
209
210static int sun4i_lradc_probe(struct platform_device *pdev)
211{
212	struct sun4i_lradc_data *lradc;
213	struct device *dev = &pdev->dev;
214	int i;
215	int error;
216
217	lradc = devm_kzalloc(dev, sizeof(struct sun4i_lradc_data), GFP_KERNEL);
218	if (!lradc)
219		return -ENOMEM;
220
221	error = sun4i_lradc_load_dt_keymap(dev, lradc);
222	if (error)
223		return error;
224
225	lradc->vref_supply = devm_regulator_get(dev, "vref");
226	if (IS_ERR(lradc->vref_supply))
227		return PTR_ERR(lradc->vref_supply);
228
229	lradc->dev = dev;
230	lradc->input = devm_input_allocate_device(dev);
231	if (!lradc->input)
232		return -ENOMEM;
233
234	lradc->input->name = pdev->name;
235	lradc->input->phys = "sun4i_lradc/input0";
236	lradc->input->open = sun4i_lradc_open;
237	lradc->input->close = sun4i_lradc_close;
238	lradc->input->id.bustype = BUS_HOST;
239	lradc->input->id.vendor = 0x0001;
240	lradc->input->id.product = 0x0001;
241	lradc->input->id.version = 0x0100;
242
243	__set_bit(EV_KEY, lradc->input->evbit);
244	for (i = 0; i < lradc->chan0_map_count; i++)
245		__set_bit(lradc->chan0_map[i].keycode, lradc->input->keybit);
246
247	input_set_drvdata(lradc->input, lradc);
248
249	lradc->base = devm_ioremap_resource(dev,
250			      platform_get_resource(pdev, IORESOURCE_MEM, 0));
251	if (IS_ERR(lradc->base))
252		return PTR_ERR(lradc->base);
253
254	error = devm_request_irq(dev, platform_get_irq(pdev, 0),
255				 sun4i_lradc_irq, 0,
256				 "sun4i-a10-lradc-keys", lradc);
257	if (error)
258		return error;
259
260	error = input_register_device(lradc->input);
261	if (error)
262		return error;
263
264	platform_set_drvdata(pdev, lradc);
265	return 0;
266}
267
268static const struct of_device_id sun4i_lradc_of_match[] = {
269	{ .compatible = "allwinner,sun4i-a10-lradc-keys", },
270	{ /* sentinel */ }
271};
272MODULE_DEVICE_TABLE(of, sun4i_lradc_of_match);
273
274static struct platform_driver sun4i_lradc_driver = {
275	.driver = {
276		.name	= "sun4i-a10-lradc-keys",
277		.of_match_table = of_match_ptr(sun4i_lradc_of_match),
278	},
279	.probe	= sun4i_lradc_probe,
280};
281
282module_platform_driver(sun4i_lradc_driver);
283
284MODULE_DESCRIPTION("Allwinner sun4i low res adc attached tablet keys driver");
285MODULE_AUTHOR("Hans de Goede <hdegoede@redhat.com>");
286MODULE_LICENSE("GPL");