1/*
2 * ChromeOS EC keyboard driver
3 *
4 * Copyright (C) 2012 Google, Inc
5 *
6 * This software is licensed under the terms of the GNU General Public
7 * License version 2, as published by the Free Software Foundation, and
8 * may be copied, distributed, and modified under those terms.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13 * GNU General Public License for more details.
14 *
15 * This driver uses the Chrome OS EC byte-level message-based protocol for
16 * communicating the keyboard state (which keys are pressed) from a keyboard EC
17 * to the AP over some bus (such as i2c, lpc, spi).  The EC does debouncing,
18 * but everything else (including deghosting) is done here.  The main
19 * motivation for this is to keep the EC firmware as simple as possible, since
20 * it cannot be easily upgraded and EC flash/IRAM space is relatively
21 * expensive.
22 */
23
24#include <linux/module.h>
25#include <linux/bitops.h>
26#include <linux/i2c.h>
27#include <linux/input.h>
28#include <linux/interrupt.h>
29#include <linux/kernel.h>
30#include <linux/platform_device.h>
31#include <linux/slab.h>
32#include <linux/input/matrix_keypad.h>
33#include <linux/mfd/cros_ec.h>
34#include <linux/mfd/cros_ec_commands.h>
35
36/*
37 * @rows: Number of rows in the keypad
38 * @cols: Number of columns in the keypad
39 * @row_shift: log2 or number of rows, rounded up
40 * @keymap_data: Matrix keymap data used to convert to keyscan values
41 * @ghost_filter: true to enable the matrix key-ghosting filter
42 * @valid_keys: bitmap of existing keys for each matrix column
43 * @old_kb_state: bitmap of keys pressed last scan
44 * @dev: Device pointer
45 * @idev: Input device
46 * @ec: Top level ChromeOS device to use to talk to EC
47 */
48struct cros_ec_keyb {
49	unsigned int rows;
50	unsigned int cols;
51	int row_shift;
52	const struct matrix_keymap_data *keymap_data;
53	bool ghost_filter;
54	uint8_t *valid_keys;
55	uint8_t *old_kb_state;
56
57	struct device *dev;
58	struct input_dev *idev;
59	struct cros_ec_device *ec;
60};
61
62
63/*
64 * Returns true when there is at least one combination of pressed keys that
65 * results in ghosting.
66 */
67static bool cros_ec_keyb_has_ghosting(struct cros_ec_keyb *ckdev, uint8_t *buf)
68{
69	int col1, col2, buf1, buf2;
70	struct device *dev = ckdev->dev;
71	uint8_t *valid_keys = ckdev->valid_keys;
72
73	/*
74	 * Ghosting happens if for any pressed key X there are other keys
75	 * pressed both in the same row and column of X as, for instance,
76	 * in the following diagram:
77	 *
78	 * . . Y . g .
79	 * . . . . . .
80	 * . . . . . .
81	 * . . X . Z .
82	 *
83	 * In this case only X, Y, and Z are pressed, but g appears to be
84	 * pressed too (see Wikipedia).
85	 */
86	for (col1 = 0; col1 < ckdev->cols; col1++) {
87		buf1 = buf[col1] & valid_keys[col1];
88		for (col2 = col1 + 1; col2 < ckdev->cols; col2++) {
89			buf2 = buf[col2] & valid_keys[col2];
90			if (hweight8(buf1 & buf2) > 1) {
91				dev_dbg(dev, "ghost found at: B[%02d]:0x%02x & B[%02d]:0x%02x",
92					col1, buf1, col2, buf2);
93				return true;
94			}
95		}
96	}
97
98	return false;
99}
100
101
102/*
103 * Compares the new keyboard state to the old one and produces key
104 * press/release events accordingly.  The keyboard state is 13 bytes (one byte
105 * per column)
106 */
107static void cros_ec_keyb_process(struct cros_ec_keyb *ckdev,
108			 uint8_t *kb_state, int len)
109{
110	struct input_dev *idev = ckdev->idev;
111	int col, row;
112	int new_state;
113	int old_state;
114	int num_cols;
115
116	num_cols = len;
117
118	if (ckdev->ghost_filter && cros_ec_keyb_has_ghosting(ckdev, kb_state)) {
119		/*
120		 * Simple-minded solution: ignore this state. The obvious
121		 * improvement is to only ignore changes to keys involved in
122		 * the ghosting, but process the other changes.
123		 */
124		dev_dbg(ckdev->dev, "ghosting found\n");
125		return;
126	}
127
128	for (col = 0; col < ckdev->cols; col++) {
129		for (row = 0; row < ckdev->rows; row++) {
130			int pos = MATRIX_SCAN_CODE(row, col, ckdev->row_shift);
131			const unsigned short *keycodes = idev->keycode;
132
133			new_state = kb_state[col] & (1 << row);
134			old_state = ckdev->old_kb_state[col] & (1 << row);
135			if (new_state != old_state) {
136				dev_dbg(ckdev->dev,
137					"changed: [r%d c%d]: byte %02x\n",
138					row, col, new_state);
139
140				input_report_key(idev, keycodes[pos],
141						 new_state);
142			}
143		}
144		ckdev->old_kb_state[col] = kb_state[col];
145	}
146	input_sync(ckdev->idev);
147}
148
149static int cros_ec_keyb_get_state(struct cros_ec_keyb *ckdev, uint8_t *kb_state)
150{
151	int ret;
152	struct cros_ec_command msg = {
153		.command = EC_CMD_MKBP_STATE,
154		.insize = ckdev->cols,
155	};
156
157	ret = cros_ec_cmd_xfer(ckdev->ec, &msg);
158	if (ret < 0)
159		return ret;
160
161	memcpy(kb_state, msg.indata, ckdev->cols);
162
163	return 0;
164}
165
166static irqreturn_t cros_ec_keyb_irq(int irq, void *data)
167{
168	struct cros_ec_keyb *ckdev = data;
169	struct cros_ec_device *ec = ckdev->ec;
170	int ret;
171	uint8_t kb_state[ckdev->cols];
172
173	if (device_may_wakeup(ec->dev))
174		pm_wakeup_event(ec->dev, 0);
175
176	ret = cros_ec_keyb_get_state(ckdev, kb_state);
177	if (ret >= 0)
178		cros_ec_keyb_process(ckdev, kb_state, ret);
179	else
180		dev_err(ec->dev, "failed to get keyboard state: %d\n", ret);
181
182	return IRQ_HANDLED;
183}
184
185static int cros_ec_keyb_open(struct input_dev *dev)
186{
187	struct cros_ec_keyb *ckdev = input_get_drvdata(dev);
188	struct cros_ec_device *ec = ckdev->ec;
189
190	return request_threaded_irq(ec->irq, NULL, cros_ec_keyb_irq,
191					IRQF_TRIGGER_LOW | IRQF_ONESHOT,
192					"cros_ec_keyb", ckdev);
193}
194
195static void cros_ec_keyb_close(struct input_dev *dev)
196{
197	struct cros_ec_keyb *ckdev = input_get_drvdata(dev);
198	struct cros_ec_device *ec = ckdev->ec;
199
200	free_irq(ec->irq, ckdev);
201}
202
203/*
204 * Walks keycodes flipping bit in buffer COLUMNS deep where bit is ROW.  Used by
205 * ghosting logic to ignore NULL or virtual keys.
206 */
207static void cros_ec_keyb_compute_valid_keys(struct cros_ec_keyb *ckdev)
208{
209	int row, col;
210	int row_shift = ckdev->row_shift;
211	unsigned short *keymap = ckdev->idev->keycode;
212	unsigned short code;
213
214	BUG_ON(ckdev->idev->keycodesize != sizeof(*keymap));
215
216	for (col = 0; col < ckdev->cols; col++) {
217		for (row = 0; row < ckdev->rows; row++) {
218			code = keymap[MATRIX_SCAN_CODE(row, col, row_shift)];
219			if (code && (code != KEY_BATTERY))
220				ckdev->valid_keys[col] |= 1 << row;
221		}
222		dev_dbg(ckdev->dev, "valid_keys[%02d] = 0x%02x\n",
223			col, ckdev->valid_keys[col]);
224	}
225}
226
227static int cros_ec_keyb_probe(struct platform_device *pdev)
228{
229	struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
230	struct device *dev = ec->dev;
231	struct cros_ec_keyb *ckdev;
232	struct input_dev *idev;
233	struct device_node *np;
234	int err;
235
236	np = pdev->dev.of_node;
237	if (!np)
238		return -ENODEV;
239
240	ckdev = devm_kzalloc(&pdev->dev, sizeof(*ckdev), GFP_KERNEL);
241	if (!ckdev)
242		return -ENOMEM;
243	err = matrix_keypad_parse_of_params(&pdev->dev, &ckdev->rows,
244					    &ckdev->cols);
245	if (err)
246		return err;
247
248	ckdev->valid_keys = devm_kzalloc(&pdev->dev, ckdev->cols, GFP_KERNEL);
249	if (!ckdev->valid_keys)
250		return -ENOMEM;
251
252	ckdev->old_kb_state = devm_kzalloc(&pdev->dev, ckdev->cols, GFP_KERNEL);
253	if (!ckdev->old_kb_state)
254		return -ENOMEM;
255
256	idev = devm_input_allocate_device(&pdev->dev);
257	if (!idev)
258		return -ENOMEM;
259
260	if (!ec->irq) {
261		dev_err(dev, "no EC IRQ specified\n");
262		return -EINVAL;
263	}
264
265	ckdev->ec = ec;
266	ckdev->dev = dev;
267	dev_set_drvdata(&pdev->dev, ckdev);
268
269	idev->name = ec->ec_name;
270	idev->phys = ec->phys_name;
271	__set_bit(EV_REP, idev->evbit);
272
273	idev->id.bustype = BUS_VIRTUAL;
274	idev->id.version = 1;
275	idev->id.product = 0;
276	idev->dev.parent = &pdev->dev;
277	idev->open = cros_ec_keyb_open;
278	idev->close = cros_ec_keyb_close;
279
280	ckdev->ghost_filter = of_property_read_bool(np,
281					"google,needs-ghost-filter");
282
283	err = matrix_keypad_build_keymap(NULL, NULL, ckdev->rows, ckdev->cols,
284					 NULL, idev);
285	if (err) {
286		dev_err(dev, "cannot build key matrix\n");
287		return err;
288	}
289
290	ckdev->row_shift = get_count_order(ckdev->cols);
291
292	input_set_capability(idev, EV_MSC, MSC_SCAN);
293	input_set_drvdata(idev, ckdev);
294	ckdev->idev = idev;
295	cros_ec_keyb_compute_valid_keys(ckdev);
296
297	err = input_register_device(ckdev->idev);
298	if (err) {
299		dev_err(dev, "cannot register input device\n");
300		return err;
301	}
302
303	return 0;
304}
305
306#ifdef CONFIG_PM_SLEEP
307/* Clear any keys in the buffer */
308static void cros_ec_keyb_clear_keyboard(struct cros_ec_keyb *ckdev)
309{
310	uint8_t old_state[ckdev->cols];
311	uint8_t new_state[ckdev->cols];
312	unsigned long duration;
313	int i, ret;
314
315	/*
316	 * Keep reading until we see that the scan state does not change.
317	 * That indicates that we are done.
318	 *
319	 * Assume that the EC keyscan buffer is at most 32 deep.
320	 */
321	duration = jiffies;
322	ret = cros_ec_keyb_get_state(ckdev, new_state);
323	for (i = 1; !ret && i < 32; i++) {
324		memcpy(old_state, new_state, sizeof(old_state));
325		ret = cros_ec_keyb_get_state(ckdev, new_state);
326		if (0 == memcmp(old_state, new_state, sizeof(old_state)))
327			break;
328	}
329	duration = jiffies - duration;
330	dev_info(ckdev->dev, "Discarded %d keyscan(s) in %dus\n", i,
331		jiffies_to_usecs(duration));
332}
333
334static int cros_ec_keyb_resume(struct device *dev)
335{
336	struct cros_ec_keyb *ckdev = dev_get_drvdata(dev);
337
338	/*
339	 * When the EC is not a wake source, then it could not have caused the
340	 * resume, so we clear the EC's key scan buffer. If the EC was a
341	 * wake source (e.g. the lid is open and the user might press a key to
342	 * wake) then the key scan buffer should be preserved.
343	 */
344	if (!ckdev->ec->was_wake_device)
345		cros_ec_keyb_clear_keyboard(ckdev);
346
347	return 0;
348}
349
350#endif
351
352static SIMPLE_DEV_PM_OPS(cros_ec_keyb_pm_ops, NULL, cros_ec_keyb_resume);
353
354#ifdef CONFIG_OF
355static const struct of_device_id cros_ec_keyb_of_match[] = {
356	{ .compatible = "google,cros-ec-keyb" },
357	{},
358};
359MODULE_DEVICE_TABLE(of, cros_ec_keyb_of_match);
360#endif
361
362static struct platform_driver cros_ec_keyb_driver = {
363	.probe = cros_ec_keyb_probe,
364	.driver = {
365		.name = "cros-ec-keyb",
366		.of_match_table = of_match_ptr(cros_ec_keyb_of_match),
367		.pm	= &cros_ec_keyb_pm_ops,
368	},
369};
370
371module_platform_driver(cros_ec_keyb_driver);
372
373MODULE_LICENSE("GPL");
374MODULE_DESCRIPTION("ChromeOS EC keyboard driver");
375MODULE_ALIAS("platform:cros-ec-keyb");
376