drivers/input/keyboard/cros_ec_keyb.c

   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 ckdev->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 static struct platform_driver cros_ec_keyb_driver = {
 352         .probe = cros_ec_keyb_probe,
 353         .driver = {
 354                 .name = "cros-ec-keyb",
 355                 .pm     = &cros_ec_keyb_pm_ops,
 356         },
 357 };
 358
 359 module_platform_driver(cros_ec_keyb_driver);
 360
 361 MODULE_LICENSE("GPL");
 362 MODULE_DESCRIPTION("ChromeOS EC keyboard driver");
 363 MODULE_ALIAS("platform:cros-ec-keyb");