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  */
48 struct 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  */
67 static 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  */
107 static 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 
149 static int cros_ec_keyb_get_state(struct cros_ec_keyb *ckdev, uint8_t *kb_state)
150 {
151 	struct cros_ec_command msg = {
152 		.version = 0,
153 		.command = EC_CMD_MKBP_STATE,
154 		.outdata = NULL,
155 		.outsize = 0,
156 		.indata = kb_state,
157 		.insize = ckdev->cols,
158 	};
159 
160 	return cros_ec_cmd_xfer(ckdev->ec, &msg);
161 }
162 
163 static irqreturn_t cros_ec_keyb_irq(int irq, void *data)
164 {
165 	struct cros_ec_keyb *ckdev = data;
166 	struct cros_ec_device *ec = ckdev->ec;
167 	int ret;
168 	uint8_t kb_state[ckdev->cols];
169 
170 	if (device_may_wakeup(ec->dev))
171 		pm_wakeup_event(ec->dev, 0);
172 
173 	ret = cros_ec_keyb_get_state(ckdev, kb_state);
174 	if (ret >= 0)
175 		cros_ec_keyb_process(ckdev, kb_state, ret);
176 	else
177 		dev_err(ec->dev, "failed to get keyboard state: %d\n", ret);
178 
179 	return IRQ_HANDLED;
180 }
181 
182 static int cros_ec_keyb_open(struct input_dev *dev)
183 {
184 	struct cros_ec_keyb *ckdev = input_get_drvdata(dev);
185 	struct cros_ec_device *ec = ckdev->ec;
186 
187 	return request_threaded_irq(ec->irq, NULL, cros_ec_keyb_irq,
188 					IRQF_TRIGGER_LOW | IRQF_ONESHOT,
189 					"cros_ec_keyb", ckdev);
190 }
191 
192 static void cros_ec_keyb_close(struct input_dev *dev)
193 {
194 	struct cros_ec_keyb *ckdev = input_get_drvdata(dev);
195 	struct cros_ec_device *ec = ckdev->ec;
196 
197 	free_irq(ec->irq, ckdev);
198 }
199 
200 /*
201  * Walks keycodes flipping bit in buffer COLUMNS deep where bit is ROW.  Used by
202  * ghosting logic to ignore NULL or virtual keys.
203  */
204 static void cros_ec_keyb_compute_valid_keys(struct cros_ec_keyb *ckdev)
205 {
206 	int row, col;
207 	int row_shift = ckdev->row_shift;
208 	unsigned short *keymap = ckdev->idev->keycode;
209 	unsigned short code;
210 
211 	BUG_ON(ckdev->idev->keycodesize != sizeof(*keymap));
212 
213 	for (col = 0; col < ckdev->cols; col++) {
214 		for (row = 0; row < ckdev->rows; row++) {
215 			code = keymap[MATRIX_SCAN_CODE(row, col, row_shift)];
216 			if (code && (code != KEY_BATTERY))
217 				ckdev->valid_keys[col] |= 1 << row;
218 		}
219 		dev_dbg(ckdev->dev, "valid_keys[%02d] = 0x%02x\n",
220 			col, ckdev->valid_keys[col]);
221 	}
222 }
223 
224 static int cros_ec_keyb_probe(struct platform_device *pdev)
225 {
226 	struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
227 	struct device *dev = ec->dev;
228 	struct cros_ec_keyb *ckdev;
229 	struct input_dev *idev;
230 	struct device_node *np;
231 	int err;
232 
233 	np = pdev->dev.of_node;
234 	if (!np)
235 		return -ENODEV;
236 
237 	ckdev = devm_kzalloc(&pdev->dev, sizeof(*ckdev), GFP_KERNEL);
238 	if (!ckdev)
239 		return -ENOMEM;
240 	err = matrix_keypad_parse_of_params(&pdev->dev, &ckdev->rows,
241 					    &ckdev->cols);
242 	if (err)
243 		return err;
244 
245 	ckdev->valid_keys = devm_kzalloc(&pdev->dev, ckdev->cols, GFP_KERNEL);
246 	if (!ckdev->valid_keys)
247 		return -ENOMEM;
248 
249 	ckdev->old_kb_state = devm_kzalloc(&pdev->dev, ckdev->cols, GFP_KERNEL);
250 	if (!ckdev->old_kb_state)
251 		return -ENOMEM;
252 
253 	idev = devm_input_allocate_device(&pdev->dev);
254 	if (!idev)
255 		return -ENOMEM;
256 
257 	if (!ec->irq) {
258 		dev_err(dev, "no EC IRQ specified\n");
259 		return -EINVAL;
260 	}
261 
262 	ckdev->ec = ec;
263 	ckdev->dev = dev;
264 	dev_set_drvdata(&pdev->dev, ckdev);
265 
266 	idev->name = ec->ec_name;
267 	idev->phys = ec->phys_name;
268 	__set_bit(EV_REP, idev->evbit);
269 
270 	idev->id.bustype = BUS_VIRTUAL;
271 	idev->id.version = 1;
272 	idev->id.product = 0;
273 	idev->dev.parent = &pdev->dev;
274 	idev->open = cros_ec_keyb_open;
275 	idev->close = cros_ec_keyb_close;
276 
277 	ckdev->ghost_filter = of_property_read_bool(np,
278 					"google,needs-ghost-filter");
279 
280 	err = matrix_keypad_build_keymap(NULL, NULL, ckdev->rows, ckdev->cols,
281 					 NULL, idev);
282 	if (err) {
283 		dev_err(dev, "cannot build key matrix\n");
284 		return err;
285 	}
286 
287 	ckdev->row_shift = get_count_order(ckdev->cols);
288 
289 	input_set_capability(idev, EV_MSC, MSC_SCAN);
290 	input_set_drvdata(idev, ckdev);
291 	ckdev->idev = idev;
292 	cros_ec_keyb_compute_valid_keys(ckdev);
293 
294 	err = input_register_device(ckdev->idev);
295 	if (err) {
296 		dev_err(dev, "cannot register input device\n");
297 		return err;
298 	}
299 
300 	return 0;
301 }
302 
303 #ifdef CONFIG_PM_SLEEP
304 /* Clear any keys in the buffer */
305 static void cros_ec_keyb_clear_keyboard(struct cros_ec_keyb *ckdev)
306 {
307 	uint8_t old_state[ckdev->cols];
308 	uint8_t new_state[ckdev->cols];
309 	unsigned long duration;
310 	int i, ret;
311 
312 	/*
313 	 * Keep reading until we see that the scan state does not change.
314 	 * That indicates that we are done.
315 	 *
316 	 * Assume that the EC keyscan buffer is at most 32 deep.
317 	 */
318 	duration = jiffies;
319 	ret = cros_ec_keyb_get_state(ckdev, new_state);
320 	for (i = 1; !ret && i < 32; i++) {
321 		memcpy(old_state, new_state, sizeof(old_state));
322 		ret = cros_ec_keyb_get_state(ckdev, new_state);
323 		if (0 == memcmp(old_state, new_state, sizeof(old_state)))
324 			break;
325 	}
326 	duration = jiffies - duration;
327 	dev_info(ckdev->dev, "Discarded %d keyscan(s) in %dus\n", i,
328 		jiffies_to_usecs(duration));
329 }
330 
331 static int cros_ec_keyb_resume(struct device *dev)
332 {
333 	struct cros_ec_keyb *ckdev = dev_get_drvdata(dev);
334 
335 	/*
336 	 * When the EC is not a wake source, then it could not have caused the
337 	 * resume, so we clear the EC's key scan buffer. If the EC was a
338 	 * wake source (e.g. the lid is open and the user might press a key to
339 	 * wake) then the key scan buffer should be preserved.
340 	 */
341 	if (ckdev->ec->was_wake_device)
342 		cros_ec_keyb_clear_keyboard(ckdev);
343 
344 	return 0;
345 }
346 
347 #endif
348 
349 static SIMPLE_DEV_PM_OPS(cros_ec_keyb_pm_ops, NULL, cros_ec_keyb_resume);
350 
351 #ifdef CONFIG_OF
352 static const struct of_device_id cros_ec_keyb_of_match[] = {
353 	{ .compatible = "google,cros-ec-keyb" },
354 	{},
355 };
356 MODULE_DEVICE_TABLE(of, cros_ec_keyb_of_match);
357 #endif
358 
359 static struct platform_driver cros_ec_keyb_driver = {
360 	.probe = cros_ec_keyb_probe,
361 	.driver = {
362 		.name = "cros-ec-keyb",
363 		.of_match_table = of_match_ptr(cros_ec_keyb_of_match),
364 		.pm	= &cros_ec_keyb_pm_ops,
365 	},
366 };
367 
368 module_platform_driver(cros_ec_keyb_driver);
369 
370 MODULE_LICENSE("GPL");
371 MODULE_DESCRIPTION("ChromeOS EC keyboard driver");
372 MODULE_ALIAS("platform:cros-ec-keyb");
373