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 = 0;
152	struct cros_ec_command *msg;
153
154	msg = kmalloc(sizeof(*msg) + ckdev->cols, GFP_KERNEL);
155	if (!msg)
156		return -ENOMEM;
157
158	msg->version = 0;
159	msg->command = EC_CMD_MKBP_STATE;
160	msg->insize = ckdev->cols;
161	msg->outsize = 0;
162
163	ret = cros_ec_cmd_xfer(ckdev->ec, msg);
164	if (ret < 0) {
165		dev_err(ckdev->dev, "Error transferring EC message %d\n", ret);
166		goto exit;
167	}
168
169	memcpy(kb_state, msg->data, ckdev->cols);
170exit:
171	kfree(msg);
172	return ret;
173}
174
175static irqreturn_t cros_ec_keyb_irq(int irq, void *data)
176{
177	struct cros_ec_keyb *ckdev = data;
178	struct cros_ec_device *ec = ckdev->ec;
179	int ret;
180	uint8_t kb_state[ckdev->cols];
181
182	if (device_may_wakeup(ec->dev))
183		pm_wakeup_event(ec->dev, 0);
184
185	ret = cros_ec_keyb_get_state(ckdev, kb_state);
186	if (ret >= 0)
187		cros_ec_keyb_process(ckdev, kb_state, ret);
188	else
189		dev_err(ec->dev, "failed to get keyboard state: %d\n", ret);
190
191	return IRQ_HANDLED;
192}
193
194static int cros_ec_keyb_open(struct input_dev *dev)
195{
196	struct cros_ec_keyb *ckdev = input_get_drvdata(dev);
197	struct cros_ec_device *ec = ckdev->ec;
198
199	return request_threaded_irq(ec->irq, NULL, cros_ec_keyb_irq,
200					IRQF_TRIGGER_LOW | IRQF_ONESHOT,
201					"cros_ec_keyb", ckdev);
202}
203
204static void cros_ec_keyb_close(struct input_dev *dev)
205{
206	struct cros_ec_keyb *ckdev = input_get_drvdata(dev);
207	struct cros_ec_device *ec = ckdev->ec;
208
209	free_irq(ec->irq, ckdev);
210}
211
212/*
213 * Walks keycodes flipping bit in buffer COLUMNS deep where bit is ROW.  Used by
214 * ghosting logic to ignore NULL or virtual keys.
215 */
216static void cros_ec_keyb_compute_valid_keys(struct cros_ec_keyb *ckdev)
217{
218	int row, col;
219	int row_shift = ckdev->row_shift;
220	unsigned short *keymap = ckdev->idev->keycode;
221	unsigned short code;
222
223	BUG_ON(ckdev->idev->keycodesize != sizeof(*keymap));
224
225	for (col = 0; col < ckdev->cols; col++) {
226		for (row = 0; row < ckdev->rows; row++) {
227			code = keymap[MATRIX_SCAN_CODE(row, col, row_shift)];
228			if (code && (code != KEY_BATTERY))
229				ckdev->valid_keys[col] |= 1 << row;
230		}
231		dev_dbg(ckdev->dev, "valid_keys[%02d] = 0x%02x\n",
232			col, ckdev->valid_keys[col]);
233	}
234}
235
236static int cros_ec_keyb_probe(struct platform_device *pdev)
237{
238	struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
239	struct device *dev = ec->dev;
240	struct cros_ec_keyb *ckdev;
241	struct input_dev *idev;
242	struct device_node *np;
243	int err;
244
245	np = pdev->dev.of_node;
246	if (!np)
247		return -ENODEV;
248
249	ckdev = devm_kzalloc(&pdev->dev, sizeof(*ckdev), GFP_KERNEL);
250	if (!ckdev)
251		return -ENOMEM;
252	err = matrix_keypad_parse_of_params(&pdev->dev, &ckdev->rows,
253					    &ckdev->cols);
254	if (err)
255		return err;
256
257	ckdev->valid_keys = devm_kzalloc(&pdev->dev, ckdev->cols, GFP_KERNEL);
258	if (!ckdev->valid_keys)
259		return -ENOMEM;
260
261	ckdev->old_kb_state = devm_kzalloc(&pdev->dev, ckdev->cols, GFP_KERNEL);
262	if (!ckdev->old_kb_state)
263		return -ENOMEM;
264
265	idev = devm_input_allocate_device(&pdev->dev);
266	if (!idev)
267		return -ENOMEM;
268
269	if (!ec->irq) {
270		dev_err(dev, "no EC IRQ specified\n");
271		return -EINVAL;
272	}
273
274	ckdev->ec = ec;
275	ckdev->dev = dev;
276	dev_set_drvdata(&pdev->dev, ckdev);
277
278	idev->name = CROS_EC_DEV_NAME;
279	idev->phys = ec->phys_name;
280	__set_bit(EV_REP, idev->evbit);
281
282	idev->id.bustype = BUS_VIRTUAL;
283	idev->id.version = 1;
284	idev->id.product = 0;
285	idev->dev.parent = &pdev->dev;
286	idev->open = cros_ec_keyb_open;
287	idev->close = cros_ec_keyb_close;
288
289	ckdev->ghost_filter = of_property_read_bool(np,
290					"google,needs-ghost-filter");
291
292	err = matrix_keypad_build_keymap(NULL, NULL, ckdev->rows, ckdev->cols,
293					 NULL, idev);
294	if (err) {
295		dev_err(dev, "cannot build key matrix\n");
296		return err;
297	}
298
299	ckdev->row_shift = get_count_order(ckdev->cols);
300
301	input_set_capability(idev, EV_MSC, MSC_SCAN);
302	input_set_drvdata(idev, ckdev);
303	ckdev->idev = idev;
304	cros_ec_keyb_compute_valid_keys(ckdev);
305
306	err = input_register_device(ckdev->idev);
307	if (err) {
308		dev_err(dev, "cannot register input device\n");
309		return err;
310	}
311
312	return 0;
313}
314
315#ifdef CONFIG_PM_SLEEP
316/* Clear any keys in the buffer */
317static void cros_ec_keyb_clear_keyboard(struct cros_ec_keyb *ckdev)
318{
319	uint8_t old_state[ckdev->cols];
320	uint8_t new_state[ckdev->cols];
321	unsigned long duration;
322	int i, ret;
323
324	/*
325	 * Keep reading until we see that the scan state does not change.
326	 * That indicates that we are done.
327	 *
328	 * Assume that the EC keyscan buffer is at most 32 deep.
329	 */
330	duration = jiffies;
331	ret = cros_ec_keyb_get_state(ckdev, new_state);
332	for (i = 1; !ret && i < 32; i++) {
333		memcpy(old_state, new_state, sizeof(old_state));
334		ret = cros_ec_keyb_get_state(ckdev, new_state);
335		if (0 == memcmp(old_state, new_state, sizeof(old_state)))
336			break;
337	}
338	duration = jiffies - duration;
339	dev_info(ckdev->dev, "Discarded %d keyscan(s) in %dus\n", i,
340		jiffies_to_usecs(duration));
341}
342
343static int cros_ec_keyb_resume(struct device *dev)
344{
345	struct cros_ec_keyb *ckdev = dev_get_drvdata(dev);
346
347	/*
348	 * When the EC is not a wake source, then it could not have caused the
349	 * resume, so we clear the EC's key scan buffer. If the EC was a
350	 * wake source (e.g. the lid is open and the user might press a key to
351	 * wake) then the key scan buffer should be preserved.
352	 */
353	if (!ckdev->ec->was_wake_device)
354		cros_ec_keyb_clear_keyboard(ckdev);
355
356	return 0;
357}
358
359#endif
360
361static SIMPLE_DEV_PM_OPS(cros_ec_keyb_pm_ops, NULL, cros_ec_keyb_resume);
362
363#ifdef CONFIG_OF
364static const struct of_device_id cros_ec_keyb_of_match[] = {
365	{ .compatible = "google,cros-ec-keyb" },
366	{},
367};
368MODULE_DEVICE_TABLE(of, cros_ec_keyb_of_match);
369#endif
370
371static struct platform_driver cros_ec_keyb_driver = {
372	.probe = cros_ec_keyb_probe,
373	.driver = {
374		.name = "cros-ec-keyb",
375		.of_match_table = of_match_ptr(cros_ec_keyb_of_match),
376		.pm	= &cros_ec_keyb_pm_ops,
377	},
378};
379
380module_platform_driver(cros_ec_keyb_driver);
381
382MODULE_LICENSE("GPL");
383MODULE_DESCRIPTION("ChromeOS EC keyboard driver");
384MODULE_ALIAS("platform:cros-ec-keyb");