uart.c

  1// SPDX-License-Identifier: GPL-2.0+
  2/*
  3 * Driver for NXP PN532 NFC Chip - UART transport layer
  4 *
  5 * Copyright (C) 2018 Lemonage Software GmbH
  6 * Author: Lars Pöschel <poeschel@lemonage.de>
  7 * All rights reserved.
  8 */
  9
 10#include <linux/device.h>
 11#include <linux/kernel.h>
 12#include <linux/module.h>
 13#include <linux/nfc.h>
 14#include <linux/netdevice.h>
 15#include <linux/of.h>
 16#include <linux/serdev.h>
 17#include "pn533.h"
 18
 19#define PN532_UART_SKB_BUFF_LEN	(PN533_CMD_DATAEXCH_DATA_MAXLEN * 2)
 20
 21enum send_wakeup {
 22	PN532_SEND_NO_WAKEUP = 0,
 23	PN532_SEND_WAKEUP,
 24	PN532_SEND_LAST_WAKEUP,
 25};
 26
 27
 28struct pn532_uart_phy {
 29	struct serdev_device *serdev;
 30	struct sk_buff *recv_skb;
 31	struct pn533 *priv;
 32	/*
 33	 * send_wakeup variable is used to control if we need to send a wakeup
 34	 * request to the pn532 chip prior to our actual command. There is a
 35	 * little propability of a race condition. We decided to not mutex the
 36	 * variable as the worst that could happen is, that we send a wakeup
 37	 * to the chip that is already awake. This does not hurt. It is a
 38	 * no-op to the chip.
 39	 */
 40	enum send_wakeup send_wakeup;
 41	struct timer_list cmd_timeout;
 42	struct sk_buff *cur_out_buf;
 43};
 44
 45static int pn532_uart_send_frame(struct pn533 *dev,
 46				struct sk_buff *out)
 47{
 48	/* wakeup sequence and dummy bytes for waiting time */
 49	static const u8 wakeup[] = {
 50		0x55, 0x55, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
 51		0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
 52	struct pn532_uart_phy *pn532 = dev->phy;
 53	int err;
 54
 55	print_hex_dump_debug("PN532_uart TX: ", DUMP_PREFIX_NONE, 16, 1,
 56			     out->data, out->len, false);
 57
 58	pn532->cur_out_buf = out;
 59	if (pn532->send_wakeup) {
 60		err = serdev_device_write(pn532->serdev,
 61				wakeup, sizeof(wakeup),
 62				MAX_SCHEDULE_TIMEOUT);
 63		if (err < 0)
 64			return err;
 65	}
 66
 67	if (pn532->send_wakeup == PN532_SEND_LAST_WAKEUP)
 68		pn532->send_wakeup = PN532_SEND_NO_WAKEUP;
 69
 70	err = serdev_device_write(pn532->serdev, out->data, out->len,
 71			MAX_SCHEDULE_TIMEOUT);
 72	if (err < 0)
 73		return err;
 74
 75	mod_timer(&pn532->cmd_timeout, HZ / 40 + jiffies);
 76	return 0;
 77}
 78
 79static int pn532_uart_send_ack(struct pn533 *dev, gfp_t flags)
 80{
 81	/* spec 7.1.1.3:  Preamble, SoPC (2), ACK Code (2), Postamble */
 82	static const u8 ack[PN533_STD_FRAME_ACK_SIZE] = {
 83			0x00, 0x00, 0xff, 0x00, 0xff, 0x00};
 84	struct pn532_uart_phy *pn532 = dev->phy;
 85	int err;
 86
 87	err = serdev_device_write(pn532->serdev, ack, sizeof(ack),
 88			MAX_SCHEDULE_TIMEOUT);
 89	if (err < 0)
 90		return err;
 91
 92	return 0;
 93}
 94
 95static void pn532_uart_abort_cmd(struct pn533 *dev, gfp_t flags)
 96{
 97	/* An ack will cancel the last issued command */
 98	pn532_uart_send_ack(dev, flags);
 99	/* schedule cmd_complete_work to finish current command execution */
100	pn533_recv_frame(dev, NULL, -ENOENT);
101}
102
103static int pn532_dev_up(struct pn533 *dev)
104{
105	struct pn532_uart_phy *pn532 = dev->phy;
106	int ret = 0;
107
108	ret = serdev_device_open(pn532->serdev);
109	if (ret)
110		return ret;
111
112	pn532->send_wakeup = PN532_SEND_LAST_WAKEUP;
113	return ret;
114}
115
116static int pn532_dev_down(struct pn533 *dev)
117{
118	struct pn532_uart_phy *pn532 = dev->phy;
119
120	serdev_device_close(pn532->serdev);
121	pn532->send_wakeup = PN532_SEND_WAKEUP;
122
123	return 0;
124}
125
126static const struct pn533_phy_ops uart_phy_ops = {
127	.send_frame = pn532_uart_send_frame,
128	.send_ack = pn532_uart_send_ack,
129	.abort_cmd = pn532_uart_abort_cmd,
130	.dev_up = pn532_dev_up,
131	.dev_down = pn532_dev_down,
132};
133
134static void pn532_cmd_timeout(struct timer_list *t)
135{
136	struct pn532_uart_phy *dev = timer_container_of(dev, t, cmd_timeout);
137
138	pn532_uart_send_frame(dev->priv, dev->cur_out_buf);
139}
140
141/*
142 * scans the buffer if it contains a pn532 frame. It is not checked if the
143 * frame is really valid. This is later done with pn533_rx_frame_is_valid.
144 * This is useful for malformed or errornous transmitted frames. Adjusts the
145 * bufferposition where the frame starts, since pn533_recv_frame expects a
146 * well formed frame.
147 */
148static int pn532_uart_rx_is_frame(struct sk_buff *skb)
149{
150	struct pn533_std_frame *std;
151	struct pn533_ext_frame *ext;
152	u16 frame_len;
153	int i;
154
155	for (i = 0; i + PN533_STD_FRAME_ACK_SIZE <= skb->len; i++) {
156		std = (struct pn533_std_frame *)&skb->data[i];
157		/* search start code */
158		if (std->start_frame != cpu_to_be16(PN533_STD_FRAME_SOF))
159			continue;
160
161		/* frame type */
162		switch (std->datalen) {
163		case PN533_FRAME_DATALEN_ACK:
164			if (std->datalen_checksum == 0xff) {
165				skb_pull(skb, i);
166				return 1;
167			}
168
169			break;
170		case PN533_FRAME_DATALEN_ERROR:
171			if ((std->datalen_checksum == 0xff) &&
172					(skb->len >=
173					 PN533_STD_ERROR_FRAME_SIZE)) {
174				skb_pull(skb, i);
175				return 1;
176			}
177
178			break;
179		case PN533_FRAME_DATALEN_EXTENDED:
180			ext = (struct pn533_ext_frame *)&skb->data[i];
181			frame_len = be16_to_cpu(ext->datalen);
182			if (skb->len >= frame_len +
183					sizeof(struct pn533_ext_frame) +
184					2 /* CKS + Postamble */) {
185				skb_pull(skb, i);
186				return 1;
187			}
188
189			break;
190		default: /* normal information frame */
191			frame_len = std->datalen;
192			if (skb->len >= frame_len +
193					sizeof(struct pn533_std_frame) +
194					2 /* CKS + Postamble */) {
195				skb_pull(skb, i);
196				return 1;
197			}
198
199			break;
200		}
201	}
202
203	return 0;
204}
205
206static size_t pn532_receive_buf(struct serdev_device *serdev,
207				const u8 *data, size_t count)
208{
209	struct pn532_uart_phy *dev = serdev_device_get_drvdata(serdev);
210	size_t i;
211
212	timer_delete(&dev->cmd_timeout);
213	for (i = 0; i < count; i++) {
214		if (!dev->recv_skb) {
215			dev->recv_skb = alloc_skb(PN532_UART_SKB_BUFF_LEN,
216						  GFP_KERNEL);
217			if (!dev->recv_skb)
218				return i;
219		}
220
221		if (unlikely(!skb_tailroom(dev->recv_skb)))
222			skb_trim(dev->recv_skb, 0);
223
224		skb_put_u8(dev->recv_skb, *data++);
225		if (!pn532_uart_rx_is_frame(dev->recv_skb))
226			continue;
227
228		pn533_recv_frame(dev->priv, dev->recv_skb, 0);
229		dev->recv_skb = NULL;
230	}
231
232	return i;
233}
234
235static const struct serdev_device_ops pn532_serdev_ops = {
236	.receive_buf = pn532_receive_buf,
237	.write_wakeup = serdev_device_write_wakeup,
238};
239
240static const struct of_device_id pn532_uart_of_match[] = {
241	{ .compatible = "nxp,pn532", },
242	{},
243};
244MODULE_DEVICE_TABLE(of, pn532_uart_of_match);
245
246static int pn532_uart_probe(struct serdev_device *serdev)
247{
248	struct pn532_uart_phy *pn532;
249	struct pn533 *priv;
250	int err;
251
252	err = -ENOMEM;
253	pn532 = kzalloc(sizeof(*pn532), GFP_KERNEL);
254	if (!pn532)
255		goto err_exit;
256
257	pn532->recv_skb = alloc_skb(PN532_UART_SKB_BUFF_LEN, GFP_KERNEL);
258	if (!pn532->recv_skb)
259		goto err_free;
260
261	pn532->serdev = serdev;
262	serdev_device_set_drvdata(serdev, pn532);
263	serdev_device_set_client_ops(serdev, &pn532_serdev_ops);
264	err = serdev_device_open(serdev);
265	if (err) {
266		dev_err(&serdev->dev, "Unable to open device\n");
267		goto err_skb;
268	}
269
270	err = serdev_device_set_baudrate(serdev, 115200);
271	if (err != 115200) {
272		err = -EINVAL;
273		goto err_serdev;
274	}
275
276	serdev_device_set_flow_control(serdev, false);
277	pn532->send_wakeup = PN532_SEND_WAKEUP;
278	timer_setup(&pn532->cmd_timeout, pn532_cmd_timeout, 0);
279	priv = pn53x_common_init(PN533_DEVICE_PN532_AUTOPOLL,
280				     PN533_PROTO_REQ_ACK_RESP,
281				     pn532, &uart_phy_ops, NULL,
282				     &pn532->serdev->dev);
283	if (IS_ERR(priv)) {
284		err = PTR_ERR(priv);
285		goto err_serdev;
286	}
287
288	pn532->priv = priv;
289	err = pn533_finalize_setup(pn532->priv);
290	if (err)
291		goto err_clean;
292
293	serdev_device_close(serdev);
294	err = pn53x_register_nfc(priv, PN533_NO_TYPE_B_PROTOCOLS, &serdev->dev);
295	if (err) {
296		pn53x_common_clean(pn532->priv);
297		goto err_skb;
298	}
299
300	return err;
301
302err_clean:
303	pn53x_common_clean(pn532->priv);
304err_serdev:
305	serdev_device_close(serdev);
306err_skb:
307	kfree_skb(pn532->recv_skb);
308err_free:
309	kfree(pn532);
310err_exit:
311	return err;
312}
313
314static void pn532_uart_remove(struct serdev_device *serdev)
315{
316	struct pn532_uart_phy *pn532 = serdev_device_get_drvdata(serdev);
317
318	pn53x_unregister_nfc(pn532->priv);
319	serdev_device_close(serdev);
320	pn53x_common_clean(pn532->priv);
321	timer_shutdown_sync(&pn532->cmd_timeout);
322	kfree_skb(pn532->recv_skb);
323	kfree(pn532);
324}
325
326static struct serdev_device_driver pn532_uart_driver = {
327	.probe = pn532_uart_probe,
328	.remove = pn532_uart_remove,
329	.driver = {
330		.name = "pn532_uart",
331		.of_match_table = pn532_uart_of_match,
332	},
333};
334
335module_serdev_device_driver(pn532_uart_driver);
336
337MODULE_AUTHOR("Lars Pöschel <poeschel@lemonage.de>");
338MODULE_DESCRIPTION("PN532 UART driver");
339MODULE_LICENSE("GPL");