1 /*
2 * HCI based Driver for Inside Secure microread NFC Chip - i2c layer
3 *
4 * Copyright (C) 2013 Intel Corporation. All rights reserved.
5 *
6 * This program is free software; you can redistribute it and/or modify it
7 * under the terms and conditions of the GNU General Public License,
8 * version 2, as published by the Free Software Foundation.
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 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, see <http://www.gnu.org/licenses/>.
17 */
18
19 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
20
21 #include <linux/module.h>
22 #include <linux/i2c.h>
23 #include <linux/delay.h>
24 #include <linux/slab.h>
25 #include <linux/interrupt.h>
26 #include <linux/gpio.h>
27
28 #include <linux/nfc.h>
29 #include <net/nfc/hci.h>
30 #include <net/nfc/llc.h>
31
32 #include "microread.h"
33
34 #define MICROREAD_I2C_DRIVER_NAME "microread"
35
36 #define MICROREAD_I2C_FRAME_HEADROOM 1
37 #define MICROREAD_I2C_FRAME_TAILROOM 1
38
39 /* framing in HCI mode */
40 #define MICROREAD_I2C_LLC_LEN 1
41 #define MICROREAD_I2C_LLC_CRC 1
42 #define MICROREAD_I2C_LLC_LEN_CRC (MICROREAD_I2C_LLC_LEN + \
43 MICROREAD_I2C_LLC_CRC)
44 #define MICROREAD_I2C_LLC_MIN_SIZE (1 + MICROREAD_I2C_LLC_LEN_CRC)
45 #define MICROREAD_I2C_LLC_MAX_PAYLOAD 29
46 #define MICROREAD_I2C_LLC_MAX_SIZE (MICROREAD_I2C_LLC_LEN_CRC + 1 + \
47 MICROREAD_I2C_LLC_MAX_PAYLOAD)
48
49 struct microread_i2c_phy {
50 struct i2c_client *i2c_dev;
51 struct nfc_hci_dev *hdev;
52
53 int hard_fault; /*
54 * < 0 if hardware error occured (e.g. i2c err)
55 * and prevents normal operation.
56 */
57 };
58
59 #define I2C_DUMP_SKB(info, skb) \
60 do { \
61 pr_debug("%s:\n", info); \
62 print_hex_dump(KERN_DEBUG, "i2c: ", DUMP_PREFIX_OFFSET, \
63 16, 1, (skb)->data, (skb)->len, 0); \
64 } while (0)
65
microread_i2c_add_len_crc(struct sk_buff * skb)66 static void microread_i2c_add_len_crc(struct sk_buff *skb)
67 {
68 int i;
69 u8 crc = 0;
70 int len;
71
72 len = skb->len;
73 *(u8 *)skb_push(skb, 1) = len;
74
75 for (i = 0; i < skb->len; i++)
76 crc = crc ^ skb->data[i];
77
78 skb_put_u8(skb, crc);
79 }
80
microread_i2c_remove_len_crc(struct sk_buff * skb)81 static void microread_i2c_remove_len_crc(struct sk_buff *skb)
82 {
83 skb_pull(skb, MICROREAD_I2C_FRAME_HEADROOM);
84 skb_trim(skb, MICROREAD_I2C_FRAME_TAILROOM);
85 }
86
check_crc(struct sk_buff * skb)87 static int check_crc(struct sk_buff *skb)
88 {
89 int i;
90 u8 crc = 0;
91
92 for (i = 0; i < skb->len - 1; i++)
93 crc = crc ^ skb->data[i];
94
95 if (crc != skb->data[skb->len-1]) {
96 pr_err("CRC error 0x%x != 0x%x\n", crc, skb->data[skb->len-1]);
97 pr_info("%s: BAD CRC\n", __func__);
98 return -EPERM;
99 }
100
101 return 0;
102 }
103
microread_i2c_enable(void * phy_id)104 static int microread_i2c_enable(void *phy_id)
105 {
106 return 0;
107 }
108
microread_i2c_disable(void * phy_id)109 static void microread_i2c_disable(void *phy_id)
110 {
111 return;
112 }
113
microread_i2c_write(void * phy_id,struct sk_buff * skb)114 static int microread_i2c_write(void *phy_id, struct sk_buff *skb)
115 {
116 int r;
117 struct microread_i2c_phy *phy = phy_id;
118 struct i2c_client *client = phy->i2c_dev;
119
120 if (phy->hard_fault != 0)
121 return phy->hard_fault;
122
123 usleep_range(3000, 6000);
124
125 microread_i2c_add_len_crc(skb);
126
127 I2C_DUMP_SKB("i2c frame written", skb);
128
129 r = i2c_master_send(client, skb->data, skb->len);
130
131 if (r == -EREMOTEIO) { /* Retry, chip was in standby */
132 usleep_range(6000, 10000);
133 r = i2c_master_send(client, skb->data, skb->len);
134 }
135
136 if (r >= 0) {
137 if (r != skb->len)
138 r = -EREMOTEIO;
139 else
140 r = 0;
141 }
142
143 microread_i2c_remove_len_crc(skb);
144
145 return r;
146 }
147
148
microread_i2c_read(struct microread_i2c_phy * phy,struct sk_buff ** skb)149 static int microread_i2c_read(struct microread_i2c_phy *phy,
150 struct sk_buff **skb)
151 {
152 int r;
153 u8 len;
154 u8 tmp[MICROREAD_I2C_LLC_MAX_SIZE - 1];
155 struct i2c_client *client = phy->i2c_dev;
156
157 r = i2c_master_recv(client, &len, 1);
158 if (r != 1) {
159 nfc_err(&client->dev, "cannot read len byte\n");
160 return -EREMOTEIO;
161 }
162
163 if ((len < MICROREAD_I2C_LLC_MIN_SIZE) ||
164 (len > MICROREAD_I2C_LLC_MAX_SIZE)) {
165 nfc_err(&client->dev, "invalid len byte\n");
166 r = -EBADMSG;
167 goto flush;
168 }
169
170 *skb = alloc_skb(1 + len, GFP_KERNEL);
171 if (*skb == NULL) {
172 r = -ENOMEM;
173 goto flush;
174 }
175
176 skb_put_u8(*skb, len);
177
178 r = i2c_master_recv(client, skb_put(*skb, len), len);
179 if (r != len) {
180 kfree_skb(*skb);
181 return -EREMOTEIO;
182 }
183
184 I2C_DUMP_SKB("cc frame read", *skb);
185
186 r = check_crc(*skb);
187 if (r != 0) {
188 kfree_skb(*skb);
189 r = -EBADMSG;
190 goto flush;
191 }
192
193 skb_pull(*skb, 1);
194 skb_trim(*skb, (*skb)->len - MICROREAD_I2C_FRAME_TAILROOM);
195
196 usleep_range(3000, 6000);
197
198 return 0;
199
200 flush:
201 if (i2c_master_recv(client, tmp, sizeof(tmp)) < 0)
202 r = -EREMOTEIO;
203
204 usleep_range(3000, 6000);
205
206 return r;
207 }
208
microread_i2c_irq_thread_fn(int irq,void * phy_id)209 static irqreturn_t microread_i2c_irq_thread_fn(int irq, void *phy_id)
210 {
211 struct microread_i2c_phy *phy = phy_id;
212 struct sk_buff *skb = NULL;
213 int r;
214
215 if (!phy || irq != phy->i2c_dev->irq) {
216 WARN_ON_ONCE(1);
217 return IRQ_NONE;
218 }
219
220 if (phy->hard_fault != 0)
221 return IRQ_HANDLED;
222
223 r = microread_i2c_read(phy, &skb);
224 if (r == -EREMOTEIO) {
225 phy->hard_fault = r;
226
227 nfc_hci_recv_frame(phy->hdev, NULL);
228
229 return IRQ_HANDLED;
230 } else if ((r == -ENOMEM) || (r == -EBADMSG)) {
231 return IRQ_HANDLED;
232 }
233
234 nfc_hci_recv_frame(phy->hdev, skb);
235
236 return IRQ_HANDLED;
237 }
238
239 static struct nfc_phy_ops i2c_phy_ops = {
240 .write = microread_i2c_write,
241 .enable = microread_i2c_enable,
242 .disable = microread_i2c_disable,
243 };
244
microread_i2c_probe(struct i2c_client * client,const struct i2c_device_id * id)245 static int microread_i2c_probe(struct i2c_client *client,
246 const struct i2c_device_id *id)
247 {
248 struct microread_i2c_phy *phy;
249 int r;
250
251 dev_dbg(&client->dev, "client %p\n", client);
252
253 phy = devm_kzalloc(&client->dev, sizeof(struct microread_i2c_phy),
254 GFP_KERNEL);
255 if (!phy)
256 return -ENOMEM;
257
258 i2c_set_clientdata(client, phy);
259 phy->i2c_dev = client;
260
261 r = request_threaded_irq(client->irq, NULL, microread_i2c_irq_thread_fn,
262 IRQF_TRIGGER_RISING | IRQF_ONESHOT,
263 MICROREAD_I2C_DRIVER_NAME, phy);
264 if (r) {
265 nfc_err(&client->dev, "Unable to register IRQ handler\n");
266 return r;
267 }
268
269 r = microread_probe(phy, &i2c_phy_ops, LLC_SHDLC_NAME,
270 MICROREAD_I2C_FRAME_HEADROOM,
271 MICROREAD_I2C_FRAME_TAILROOM,
272 MICROREAD_I2C_LLC_MAX_PAYLOAD, &phy->hdev);
273 if (r < 0)
274 goto err_irq;
275
276 nfc_info(&client->dev, "Probed\n");
277
278 return 0;
279
280 err_irq:
281 free_irq(client->irq, phy);
282
283 return r;
284 }
285
microread_i2c_remove(struct i2c_client * client)286 static int microread_i2c_remove(struct i2c_client *client)
287 {
288 struct microread_i2c_phy *phy = i2c_get_clientdata(client);
289
290 microread_remove(phy->hdev);
291
292 free_irq(client->irq, phy);
293
294 return 0;
295 }
296
297 static const struct i2c_device_id microread_i2c_id[] = {
298 { MICROREAD_I2C_DRIVER_NAME, 0},
299 { }
300 };
301 MODULE_DEVICE_TABLE(i2c, microread_i2c_id);
302
303 static struct i2c_driver microread_i2c_driver = {
304 .driver = {
305 .name = MICROREAD_I2C_DRIVER_NAME,
306 },
307 .probe = microread_i2c_probe,
308 .remove = microread_i2c_remove,
309 .id_table = microread_i2c_id,
310 };
311
312 module_i2c_driver(microread_i2c_driver);
313
314 MODULE_LICENSE("GPL");
315 MODULE_DESCRIPTION(DRIVER_DESC);
316
