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
49struct microread_i2c_phy {
50	struct i2c_client *i2c_dev;
51	struct nfc_hci_dev *hdev;
52
53	int irq;
54
55	int hard_fault;		/*
56				 * < 0 if hardware error occured (e.g. i2c err)
57				 * and prevents normal operation.
58				 */
59};
60
61#define I2C_DUMP_SKB(info, skb)					\
62do {								\
63	pr_debug("%s:\n", info);				\
64	print_hex_dump(KERN_DEBUG, "i2c: ", DUMP_PREFIX_OFFSET,	\
65		       16, 1, (skb)->data, (skb)->len, 0);	\
66} while (0)
67
68static void microread_i2c_add_len_crc(struct sk_buff *skb)
69{
70	int i;
71	u8 crc = 0;
72	int len;
73
74	len = skb->len;
75	*skb_push(skb, 1) = len;
76
77	for (i = 0; i < skb->len; i++)
78		crc = crc ^ skb->data[i];
79
80	*skb_put(skb, 1) = crc;
81}
82
83static void microread_i2c_remove_len_crc(struct sk_buff *skb)
84{
85	skb_pull(skb, MICROREAD_I2C_FRAME_HEADROOM);
86	skb_trim(skb, MICROREAD_I2C_FRAME_TAILROOM);
87}
88
89static int check_crc(struct sk_buff *skb)
90{
91	int i;
92	u8 crc = 0;
93
94	for (i = 0; i < skb->len - 1; i++)
95		crc = crc ^ skb->data[i];
96
97	if (crc != skb->data[skb->len-1]) {
98		pr_err("CRC error 0x%x != 0x%x\n", crc, skb->data[skb->len-1]);
99		pr_info("%s: BAD CRC\n", __func__);
100		return -EPERM;
101	}
102
103	return 0;
104}
105
106static int microread_i2c_enable(void *phy_id)
107{
108	return 0;
109}
110
111static void microread_i2c_disable(void *phy_id)
112{
113	return;
114}
115
116static int microread_i2c_write(void *phy_id, struct sk_buff *skb)
117{
118	int r;
119	struct microread_i2c_phy *phy = phy_id;
120	struct i2c_client *client = phy->i2c_dev;
121
122	if (phy->hard_fault != 0)
123		return phy->hard_fault;
124
125	usleep_range(3000, 6000);
126
127	microread_i2c_add_len_crc(skb);
128
129	I2C_DUMP_SKB("i2c frame written", skb);
130
131	r = i2c_master_send(client, skb->data, skb->len);
132
133	if (r == -EREMOTEIO) {	/* Retry, chip was in standby */
134		usleep_range(6000, 10000);
135		r = i2c_master_send(client, skb->data, skb->len);
136	}
137
138	if (r >= 0) {
139		if (r != skb->len)
140			r = -EREMOTEIO;
141		else
142			r = 0;
143	}
144
145	microread_i2c_remove_len_crc(skb);
146
147	return r;
148}
149
150
151static int microread_i2c_read(struct microread_i2c_phy *phy,
152			      struct sk_buff **skb)
153{
154	int r;
155	u8 len;
156	u8 tmp[MICROREAD_I2C_LLC_MAX_SIZE - 1];
157	struct i2c_client *client = phy->i2c_dev;
158
159	r = i2c_master_recv(client, &len, 1);
160	if (r != 1) {
161		nfc_err(&client->dev, "cannot read len byte\n");
162		return -EREMOTEIO;
163	}
164
165	if ((len < MICROREAD_I2C_LLC_MIN_SIZE) ||
166	    (len > MICROREAD_I2C_LLC_MAX_SIZE)) {
167		nfc_err(&client->dev, "invalid len byte\n");
168		r = -EBADMSG;
169		goto flush;
170	}
171
172	*skb = alloc_skb(1 + len, GFP_KERNEL);
173	if (*skb == NULL) {
174		r = -ENOMEM;
175		goto flush;
176	}
177
178	*skb_put(*skb, 1) = len;
179
180	r = i2c_master_recv(client, skb_put(*skb, len), len);
181	if (r != len) {
182		kfree_skb(*skb);
183		return -EREMOTEIO;
184	}
185
186	I2C_DUMP_SKB("cc frame read", *skb);
187
188	r = check_crc(*skb);
189	if (r != 0) {
190		kfree_skb(*skb);
191		r = -EBADMSG;
192		goto flush;
193	}
194
195	skb_pull(*skb, 1);
196	skb_trim(*skb, (*skb)->len - MICROREAD_I2C_FRAME_TAILROOM);
197
198	usleep_range(3000, 6000);
199
200	return 0;
201
202flush:
203	if (i2c_master_recv(client, tmp, sizeof(tmp)) < 0)
204		r = -EREMOTEIO;
205
206	usleep_range(3000, 6000);
207
208	return r;
209}
210
211static irqreturn_t microread_i2c_irq_thread_fn(int irq, void *phy_id)
212{
213	struct microread_i2c_phy *phy = phy_id;
214	struct i2c_client *client;
215	struct sk_buff *skb = NULL;
216	int r;
217
218	if (!phy || irq != phy->i2c_dev->irq) {
219		WARN_ON_ONCE(1);
220		return IRQ_NONE;
221	}
222
223	client = phy->i2c_dev;
224
225	if (phy->hard_fault != 0)
226		return IRQ_HANDLED;
227
228	r = microread_i2c_read(phy, &skb);
229	if (r == -EREMOTEIO) {
230		phy->hard_fault = r;
231
232		nfc_hci_recv_frame(phy->hdev, NULL);
233
234		return IRQ_HANDLED;
235	} else if ((r == -ENOMEM) || (r == -EBADMSG)) {
236		return IRQ_HANDLED;
237	}
238
239	nfc_hci_recv_frame(phy->hdev, skb);
240
241	return IRQ_HANDLED;
242}
243
244static struct nfc_phy_ops i2c_phy_ops = {
245	.write = microread_i2c_write,
246	.enable = microread_i2c_enable,
247	.disable = microread_i2c_disable,
248};
249
250static int microread_i2c_probe(struct i2c_client *client,
251			       const struct i2c_device_id *id)
252{
253	struct microread_i2c_phy *phy;
254	struct microread_nfc_platform_data *pdata =
255		dev_get_platdata(&client->dev);
256	int r;
257
258	dev_dbg(&client->dev, "client %p\n", client);
259
260	if (!pdata) {
261		nfc_err(&client->dev, "client %p: missing platform data\n",
262			client);
263		return -EINVAL;
264	}
265
266	phy = devm_kzalloc(&client->dev, sizeof(struct microread_i2c_phy),
267			   GFP_KERNEL);
268	if (!phy)
269		return -ENOMEM;
270
271	i2c_set_clientdata(client, phy);
272	phy->i2c_dev = client;
273
274	r = request_threaded_irq(client->irq, NULL, microread_i2c_irq_thread_fn,
275				 IRQF_TRIGGER_RISING | IRQF_ONESHOT,
276				 MICROREAD_I2C_DRIVER_NAME, phy);
277	if (r) {
278		nfc_err(&client->dev, "Unable to register IRQ handler\n");
279		return r;
280	}
281
282	r = microread_probe(phy, &i2c_phy_ops, LLC_SHDLC_NAME,
283			    MICROREAD_I2C_FRAME_HEADROOM,
284			    MICROREAD_I2C_FRAME_TAILROOM,
285			    MICROREAD_I2C_LLC_MAX_PAYLOAD, &phy->hdev);
286	if (r < 0)
287		goto err_irq;
288
289	nfc_info(&client->dev, "Probed\n");
290
291	return 0;
292
293err_irq:
294	free_irq(client->irq, phy);
295
296	return r;
297}
298
299static int microread_i2c_remove(struct i2c_client *client)
300{
301	struct microread_i2c_phy *phy = i2c_get_clientdata(client);
302
303	microread_remove(phy->hdev);
304
305	free_irq(client->irq, phy);
306
307	return 0;
308}
309
310static struct i2c_device_id microread_i2c_id[] = {
311	{ MICROREAD_I2C_DRIVER_NAME, 0},
312	{ }
313};
314MODULE_DEVICE_TABLE(i2c, microread_i2c_id);
315
316static struct i2c_driver microread_i2c_driver = {
317	.driver = {
318		.name = MICROREAD_I2C_DRIVER_NAME,
319	},
320	.probe		= microread_i2c_probe,
321	.remove		= microread_i2c_remove,
322	.id_table	= microread_i2c_id,
323};
324
325module_i2c_driver(microread_i2c_driver);
326
327MODULE_LICENSE("GPL");
328MODULE_DESCRIPTION(DRIVER_DESC);
329