1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Support for the custom fast charging protocol found on the Lenovo Yoga
4 * Tablet 2 1380F / 1380L models.
5 *
6 * Copyright (C) 2024 Hans de Goede <hansg@kernel.org>
7 */
8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
9
10 #include <linux/delay.h>
11 #include <linux/err.h>
12 #include <linux/errno.h>
13 #include <linux/extcon.h>
14 #include <linux/gpio/consumer.h>
15 #include <linux/module.h>
16 #include <linux/notifier.h>
17 #include <linux/pinctrl/consumer.h>
18 #include <linux/pinctrl/machine.h>
19 #include <linux/platform_device.h>
20 #include <linux/serdev.h>
21 #include <linux/time.h>
22 #include <linux/types.h>
23 #include <linux/workqueue.h>
24 #include "../serdev_helpers.h"
25
26 #define YT2_1380_FC_PDEV_NAME "lenovo-yoga-tab2-pro-1380-fastcharger"
27 #define YT2_1380_FC_SERDEV_CTRL "serial0"
28 #define YT2_1380_FC_SERDEV_NAME "serial0-0"
29 #define YT2_1380_FC_EXTCON_NAME "i2c-lc824206xa"
30
31 #define YT2_1380_FC_MAX_TRIES 5
32 #define YT2_1380_FC_PIN_SW_DELAY_US (10 * USEC_PER_MSEC)
33 #define YT2_1380_FC_UART_DRAIN_DELAY_US (50 * USEC_PER_MSEC)
34 #define YT2_1380_FC_VOLT_SW_DELAY_US (1000 * USEC_PER_MSEC)
35
36 struct yt2_1380_fc {
37 struct device *dev;
38 struct pinctrl *pinctrl;
39 struct pinctrl_state *gpio_state;
40 struct pinctrl_state *uart_state;
41 struct gpio_desc *uart3_txd;
42 struct gpio_desc *uart3_rxd;
43 struct extcon_dev *extcon;
44 struct notifier_block nb;
45 struct work_struct work;
46 bool fast_charging;
47 };
48
yt2_1380_fc_set_gpio_mode(struct yt2_1380_fc * fc,bool enable)49 static int yt2_1380_fc_set_gpio_mode(struct yt2_1380_fc *fc, bool enable)
50 {
51 struct pinctrl_state *state = enable ? fc->gpio_state : fc->uart_state;
52 int ret;
53
54 ret = pinctrl_select_state(fc->pinctrl, state);
55 if (ret) {
56 dev_err(fc->dev, "Error %d setting pinctrl state\n", ret);
57 return ret;
58 }
59
60 fsleep(YT2_1380_FC_PIN_SW_DELAY_US);
61 return 0;
62 }
63
yt2_1380_fc_dedicated_charger_connected(struct yt2_1380_fc * fc)64 static bool yt2_1380_fc_dedicated_charger_connected(struct yt2_1380_fc *fc)
65 {
66 return extcon_get_state(fc->extcon, EXTCON_CHG_USB_DCP) > 0;
67 }
68
yt2_1380_fc_fast_charger_connected(struct yt2_1380_fc * fc)69 static bool yt2_1380_fc_fast_charger_connected(struct yt2_1380_fc *fc)
70 {
71 return extcon_get_state(fc->extcon, EXTCON_CHG_USB_FAST) > 0;
72 }
73
yt2_1380_fc_worker(struct work_struct * work)74 static void yt2_1380_fc_worker(struct work_struct *work)
75 {
76 struct yt2_1380_fc *fc = container_of(work, struct yt2_1380_fc, work);
77 int i, ret;
78
79 /* Do nothing if already fast charging */
80 if (yt2_1380_fc_fast_charger_connected(fc))
81 return;
82
83 for (i = 0; i < YT2_1380_FC_MAX_TRIES; i++) {
84 /* Set pins to UART mode (for charger disconnect and retries) */
85 ret = yt2_1380_fc_set_gpio_mode(fc, false);
86 if (ret)
87 return;
88
89 /* Only try 12V charging if a dedicated charger is detected */
90 if (!yt2_1380_fc_dedicated_charger_connected(fc))
91 return;
92
93 /* Send the command to switch to 12V charging */
94 ret = serdev_device_write_buf(to_serdev_device(fc->dev), "SC", strlen("SC"));
95 if (ret != strlen("SC")) {
96 dev_err(fc->dev, "Error %d writing to uart\n", ret);
97 return;
98 }
99
100 fsleep(YT2_1380_FC_UART_DRAIN_DELAY_US);
101
102 /* Re-check a charger is still connected */
103 if (!yt2_1380_fc_dedicated_charger_connected(fc))
104 return;
105
106 /*
107 * Now switch the lines to GPIO (output, high). The charger
108 * expects the lines being driven high after the command.
109 * Presumably this is used to detect the tablet getting
110 * unplugged (to switch back to 5V output on unplug).
111 */
112 ret = yt2_1380_fc_set_gpio_mode(fc, true);
113 if (ret)
114 return;
115
116 fsleep(YT2_1380_FC_VOLT_SW_DELAY_US);
117
118 if (yt2_1380_fc_fast_charger_connected(fc))
119 return; /* Success */
120 }
121
122 dev_dbg(fc->dev, "Failed to switch to 12V charging (not the original charger?)\n");
123 /* Failed to enable 12V fast charging, reset pins to default UART mode */
124 yt2_1380_fc_set_gpio_mode(fc, false);
125 }
126
yt2_1380_fc_extcon_evt(struct notifier_block * nb,unsigned long event,void * param)127 static int yt2_1380_fc_extcon_evt(struct notifier_block *nb,
128 unsigned long event, void *param)
129 {
130 struct yt2_1380_fc *fc = container_of(nb, struct yt2_1380_fc, nb);
131
132 schedule_work(&fc->work);
133 return NOTIFY_OK;
134 }
135
yt2_1380_fc_receive(struct serdev_device * serdev,const u8 * data,size_t len)136 static size_t yt2_1380_fc_receive(struct serdev_device *serdev, const u8 *data, size_t len)
137 {
138 /*
139 * Since the USB data lines are shorted for DCP detection, echos of
140 * the "SC" command send in yt2_1380_fc_worker() will be received.
141 */
142 dev_dbg(&serdev->dev, "recv: %*ph\n", (int)len, data);
143 return len;
144 }
145
146 static const struct serdev_device_ops yt2_1380_fc_serdev_ops = {
147 .receive_buf = yt2_1380_fc_receive,
148 .write_wakeup = serdev_device_write_wakeup,
149 };
150
yt2_1380_fc_serdev_probe(struct serdev_device * serdev)151 static int yt2_1380_fc_serdev_probe(struct serdev_device *serdev)
152 {
153 struct device *dev = &serdev->dev;
154 struct yt2_1380_fc *fc;
155 int ret;
156
157 fc = devm_kzalloc(dev, sizeof(*fc), GFP_KERNEL);
158 if (!fc)
159 return -ENOMEM;
160
161 fc->dev = dev;
162 fc->nb.notifier_call = yt2_1380_fc_extcon_evt;
163 INIT_WORK(&fc->work, yt2_1380_fc_worker);
164
165 /*
166 * Do this first since it may return -EPROBE_DEFER.
167 * There is no extcon_put(), so there is no need to free this.
168 */
169 fc->extcon = extcon_get_extcon_dev(YT2_1380_FC_EXTCON_NAME);
170 if (IS_ERR(fc->extcon))
171 return dev_err_probe(dev, PTR_ERR(fc->extcon), "getting extcon\n");
172
173 fc->pinctrl = devm_pinctrl_get(dev);
174 if (IS_ERR(fc->pinctrl))
175 return dev_err_probe(dev, PTR_ERR(fc->pinctrl), "getting pinctrl\n");
176
177 /*
178 * To switch the UART3 pins connected to the USB data lines between
179 * UART and GPIO modes.
180 */
181 fc->gpio_state = pinctrl_lookup_state(fc->pinctrl, "uart3_gpio");
182 fc->uart_state = pinctrl_lookup_state(fc->pinctrl, "uart3_uart");
183 if (IS_ERR(fc->gpio_state) || IS_ERR(fc->uart_state))
184 return dev_err_probe(dev, -EINVAL, "getting pinctrl states\n");
185
186 ret = yt2_1380_fc_set_gpio_mode(fc, true);
187 if (ret)
188 return ret;
189
190 fc->uart3_txd = devm_gpiod_get(dev, "uart3_txd", GPIOD_OUT_HIGH);
191 if (IS_ERR(fc->uart3_txd))
192 return dev_err_probe(dev, PTR_ERR(fc->uart3_txd), "getting uart3_txd gpio\n");
193
194 fc->uart3_rxd = devm_gpiod_get(dev, "uart3_rxd", GPIOD_OUT_HIGH);
195 if (IS_ERR(fc->uart3_rxd))
196 return dev_err_probe(dev, PTR_ERR(fc->uart3_rxd), "getting uart3_rxd gpio\n");
197
198 ret = yt2_1380_fc_set_gpio_mode(fc, false);
199 if (ret)
200 return ret;
201
202 serdev_device_set_drvdata(serdev, fc);
203 serdev_device_set_client_ops(serdev, &yt2_1380_fc_serdev_ops);
204
205 ret = devm_serdev_device_open(dev, serdev);
206 if (ret)
207 return dev_err_probe(dev, ret, "opening UART device\n");
208
209 serdev_device_set_baudrate(serdev, 600);
210 serdev_device_set_flow_control(serdev, false);
211
212 ret = devm_extcon_register_notifier_all(dev, fc->extcon, &fc->nb);
213 if (ret)
214 return dev_err_probe(dev, ret, "registering extcon notifier\n");
215
216 /* In case the extcon already has detected a DCP charger */
217 schedule_work(&fc->work);
218
219 return 0;
220 }
221
222 static struct serdev_device_driver yt2_1380_fc_serdev_driver = {
223 .probe = yt2_1380_fc_serdev_probe,
224 .driver = {
225 .name = KBUILD_MODNAME,
226 },
227 };
228
229 static const struct pinctrl_map yt2_1380_fc_pinctrl_map[] = {
230 PIN_MAP_MUX_GROUP(YT2_1380_FC_SERDEV_NAME, "uart3_uart",
231 "INT33FC:00", "uart3_grp", "uart"),
232 PIN_MAP_MUX_GROUP(YT2_1380_FC_SERDEV_NAME, "uart3_gpio",
233 "INT33FC:00", "uart3_grp_gpio", "gpio"),
234 };
235
yt2_1380_fc_pdev_probe(struct platform_device * pdev)236 static int yt2_1380_fc_pdev_probe(struct platform_device *pdev)
237 {
238 struct serdev_device *serdev;
239 struct device *ctrl_dev;
240 int ret;
241
242 /* Register pinctrl mappings for setting the UART3 pins mode */
243 ret = devm_pinctrl_register_mappings(&pdev->dev, yt2_1380_fc_pinctrl_map,
244 ARRAY_SIZE(yt2_1380_fc_pinctrl_map));
245 if (ret)
246 return ret;
247
248 /* And create the serdev to talk to the charger over the UART3 pins */
249 ctrl_dev = get_serdev_controller("PNP0501", "1", 0, YT2_1380_FC_SERDEV_CTRL);
250 if (IS_ERR(ctrl_dev))
251 return PTR_ERR(ctrl_dev);
252
253 serdev = serdev_device_alloc(to_serdev_controller(ctrl_dev));
254 put_device(ctrl_dev);
255 if (!serdev)
256 return -ENOMEM;
257
258 ret = serdev_device_add(serdev);
259 if (ret) {
260 serdev_device_put(serdev);
261 return dev_err_probe(&pdev->dev, ret, "adding serdev\n");
262 }
263
264 /*
265 * serdev device <-> driver matching relies on OF or ACPI matches and
266 * neither is available here, manually bind the driver.
267 */
268 ret = device_driver_attach(&yt2_1380_fc_serdev_driver.driver, &serdev->dev);
269 if (ret) {
270 /* device_driver_attach() maps EPROBE_DEFER to EAGAIN, map it back */
271 serdev_device_remove(serdev);
272 return dev_err_probe(&pdev->dev,
273 (ret == -EAGAIN) ? -EPROBE_DEFER : ret,
274 "attaching serdev driver\n");
275 }
276
277 /* So that yt2_1380_fc_pdev_remove() can remove the serdev */
278 platform_set_drvdata(pdev, serdev);
279 return 0;
280 }
281
yt2_1380_fc_pdev_remove(struct platform_device * pdev)282 static void yt2_1380_fc_pdev_remove(struct platform_device *pdev)
283 {
284 struct serdev_device *serdev = platform_get_drvdata(pdev);
285
286 serdev_device_remove(serdev);
287 }
288
289 static struct platform_driver yt2_1380_fc_pdev_driver = {
290 .probe = yt2_1380_fc_pdev_probe,
291 .remove = yt2_1380_fc_pdev_remove,
292 .driver = {
293 .name = YT2_1380_FC_PDEV_NAME,
294 .probe_type = PROBE_PREFER_ASYNCHRONOUS,
295 },
296 };
297
yt2_1380_fc_module_init(void)298 static int __init yt2_1380_fc_module_init(void)
299 {
300 int ret;
301
302 /*
303 * serdev driver MUST be registered first because pdev driver calls
304 * device_driver_attach() on the serdev, serdev-driver pair.
305 */
306 ret = serdev_device_driver_register(&yt2_1380_fc_serdev_driver);
307 if (ret)
308 return ret;
309
310 ret = platform_driver_register(&yt2_1380_fc_pdev_driver);
311 if (ret)
312 serdev_device_driver_unregister(&yt2_1380_fc_serdev_driver);
313
314 return ret;
315 }
316 module_init(yt2_1380_fc_module_init);
317
yt2_1380_fc_module_exit(void)318 static void __exit yt2_1380_fc_module_exit(void)
319 {
320 platform_driver_unregister(&yt2_1380_fc_pdev_driver);
321 serdev_device_driver_unregister(&yt2_1380_fc_serdev_driver);
322 }
323 module_exit(yt2_1380_fc_module_exit);
324
325 MODULE_ALIAS("platform:" YT2_1380_FC_PDEV_NAME);
326 MODULE_DESCRIPTION("Lenovo Yoga Tablet 2 1380 fast charge driver");
327 MODULE_AUTHOR("Hans de Goede <hansg@kernel.org>");
328 MODULE_LICENSE("GPL");
329