1/*
  2 * Copyright (C) 2013  Intel Corporation. All rights reserved.
  3 *
  4 * This program is free software; you can redistribute it and/or modify it
  5 * under the terms and conditions of the GNU General Public License,
  6 * version 2, as published by the Free Software Foundation.
  7 *
  8 * This program is distributed in the hope it will be useful, but WITHOUT
  9 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 10 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 11 * more details.
 12 *
 13 * You should have received a copy of the GNU General Public License along with
 14 * this program; if not, write to the Free Software Foundation, Inc.,
 15 * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
 16 *
 17 */
 18
 19#define pr_fmt(fmt) "nci_spi: %s: " fmt, __func__
 20
 21#include <linux/module.h>
 22
 23#include <linux/export.h>
 24#include <linux/spi/spi.h>
 25#include <linux/crc-ccitt.h>
 26#include <net/nfc/nci_core.h>
 27
 28#define NCI_SPI_ACK_SHIFT		6
 29#define NCI_SPI_MSB_PAYLOAD_MASK	0x3F
 30
 31#define NCI_SPI_SEND_TIMEOUT	(NCI_CMD_TIMEOUT > NCI_DATA_TIMEOUT ? \
 32					NCI_CMD_TIMEOUT : NCI_DATA_TIMEOUT)
 33
 34#define NCI_SPI_DIRECT_WRITE	0x01
 35#define NCI_SPI_DIRECT_READ	0x02
 36
 37#define ACKNOWLEDGE_NONE	0
 38#define ACKNOWLEDGE_ACK		1
 39#define ACKNOWLEDGE_NACK	2
 40
 41#define CRC_INIT		0xFFFF
 42
 43static int __nci_spi_send(struct nci_spi *nspi, struct sk_buff *skb,
 44			  int cs_change)
 45{
 46	struct spi_message m;
 47	struct spi_transfer t;
 48
 49	memset(&t, 0, sizeof(struct spi_transfer));
 50	/* a NULL skb means we just want the SPI chip select line to raise */
 51	if (skb) {
 52		t.tx_buf = skb->data;
 53		t.len = skb->len;
 54	} else {
 55		/* still set tx_buf non NULL to make the driver happy */
 56		t.tx_buf = &t;
 57		t.len = 0;
 58	}
 59	t.cs_change = cs_change;
 60	t.delay_usecs = nspi->xfer_udelay;
 61	t.speed_hz = nspi->xfer_speed_hz;
 62
 63	spi_message_init(&m);
 64	spi_message_add_tail(&t, &m);
 65
 66	return spi_sync(nspi->spi, &m);
 67}
 68
 69int nci_spi_send(struct nci_spi *nspi,
 70		 struct completion *write_handshake_completion,
 71		 struct sk_buff *skb)
 72{
 73	unsigned int payload_len = skb->len;
 74	unsigned char *hdr;
 75	int ret;
 76	long completion_rc;
 77
 78	/* add the NCI SPI header to the start of the buffer */
 79	hdr = skb_push(skb, NCI_SPI_HDR_LEN);
 80	hdr[0] = NCI_SPI_DIRECT_WRITE;
 81	hdr[1] = nspi->acknowledge_mode;
 82	hdr[2] = payload_len >> 8;
 83	hdr[3] = payload_len & 0xFF;
 84
 85	if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) {
 86		u16 crc;
 87
 88		crc = crc_ccitt(CRC_INIT, skb->data, skb->len);
 89		*skb_put(skb, 1) = crc >> 8;
 90		*skb_put(skb, 1) = crc & 0xFF;
 91	}
 92
 93	if (write_handshake_completion)	{
 94		/* Trick SPI driver to raise chip select */
 95		ret = __nci_spi_send(nspi, NULL, 1);
 96		if (ret)
 97			goto done;
 98
 99		/* wait for NFC chip hardware handshake to complete */
100		if (wait_for_completion_timeout(write_handshake_completion,
101						msecs_to_jiffies(1000)) == 0) {
102			ret = -ETIME;
103			goto done;
104		}
105	}
106
107	ret = __nci_spi_send(nspi, skb, 0);
108	if (ret != 0 || nspi->acknowledge_mode == NCI_SPI_CRC_DISABLED)
109		goto done;
110
111	reinit_completion(&nspi->req_completion);
112	completion_rc =	wait_for_completion_interruptible_timeout(
113							&nspi->req_completion,
114							NCI_SPI_SEND_TIMEOUT);
115
116	if (completion_rc <= 0 || nspi->req_result == ACKNOWLEDGE_NACK)
117		ret = -EIO;
118
119done:
120	kfree_skb(skb);
121
122	return ret;
123}
124EXPORT_SYMBOL_GPL(nci_spi_send);
125
126/* ---- Interface to NCI SPI drivers ---- */
127
128/**
129 * nci_spi_allocate_spi - allocate a new nci spi
130 *
131 * @spi: SPI device
132 * @acknowledge_mode: Acknowledge mode used by the NFC device
133 * @delay: delay between transactions in us
134 * @ndev: nci dev to send incoming nci frames to
135 */
136struct nci_spi *nci_spi_allocate_spi(struct spi_device *spi,
137				     u8 acknowledge_mode, unsigned int delay,
138				     struct nci_dev *ndev)
139{
140	struct nci_spi *nspi;
141
142	nspi = devm_kzalloc(&spi->dev, sizeof(struct nci_spi), GFP_KERNEL);
143	if (!nspi)
144		return NULL;
145
146	nspi->acknowledge_mode = acknowledge_mode;
147	nspi->xfer_udelay = delay;
148	/* Use controller max SPI speed by default */
149	nspi->xfer_speed_hz = 0;
150	nspi->spi = spi;
151	nspi->ndev = ndev;
152	init_completion(&nspi->req_completion);
153
154	return nspi;
155}
156EXPORT_SYMBOL_GPL(nci_spi_allocate_spi);
157
158static int send_acknowledge(struct nci_spi *nspi, u8 acknowledge)
159{
160	struct sk_buff *skb;
161	unsigned char *hdr;
162	u16 crc;
163	int ret;
164
165	skb = nci_skb_alloc(nspi->ndev, 0, GFP_KERNEL);
166
167	/* add the NCI SPI header to the start of the buffer */
168	hdr = skb_push(skb, NCI_SPI_HDR_LEN);
169	hdr[0] = NCI_SPI_DIRECT_WRITE;
170	hdr[1] = NCI_SPI_CRC_ENABLED;
171	hdr[2] = acknowledge << NCI_SPI_ACK_SHIFT;
172	hdr[3] = 0;
173
174	crc = crc_ccitt(CRC_INIT, skb->data, skb->len);
175	*skb_put(skb, 1) = crc >> 8;
176	*skb_put(skb, 1) = crc & 0xFF;
177
178	ret = __nci_spi_send(nspi, skb, 0);
179
180	kfree_skb(skb);
181
182	return ret;
183}
184
185static struct sk_buff *__nci_spi_read(struct nci_spi *nspi)
186{
187	struct sk_buff *skb;
188	struct spi_message m;
189	unsigned char req[2], resp_hdr[2];
190	struct spi_transfer tx, rx;
191	unsigned short rx_len = 0;
192	int ret;
193
194	spi_message_init(&m);
195
196	memset(&tx, 0, sizeof(struct spi_transfer));
197	req[0] = NCI_SPI_DIRECT_READ;
198	req[1] = nspi->acknowledge_mode;
199	tx.tx_buf = req;
200	tx.len = 2;
201	tx.cs_change = 0;
202	tx.speed_hz = nspi->xfer_speed_hz;
203	spi_message_add_tail(&tx, &m);
204
205	memset(&rx, 0, sizeof(struct spi_transfer));
206	rx.rx_buf = resp_hdr;
207	rx.len = 2;
208	rx.cs_change = 1;
209	rx.speed_hz = nspi->xfer_speed_hz;
210	spi_message_add_tail(&rx, &m);
211
212	ret = spi_sync(nspi->spi, &m);
213	if (ret)
214		return NULL;
215
216	if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED)
217		rx_len = ((resp_hdr[0] & NCI_SPI_MSB_PAYLOAD_MASK) << 8) +
218				resp_hdr[1] + NCI_SPI_CRC_LEN;
219	else
220		rx_len = (resp_hdr[0] << 8) | resp_hdr[1];
221
222	skb = nci_skb_alloc(nspi->ndev, rx_len, GFP_KERNEL);
223	if (!skb)
224		return NULL;
225
226	spi_message_init(&m);
227
228	memset(&rx, 0, sizeof(struct spi_transfer));
229	rx.rx_buf = skb_put(skb, rx_len);
230	rx.len = rx_len;
231	rx.cs_change = 0;
232	rx.delay_usecs = nspi->xfer_udelay;
233	rx.speed_hz = nspi->xfer_speed_hz;
234	spi_message_add_tail(&rx, &m);
235
236	ret = spi_sync(nspi->spi, &m);
237	if (ret)
238		goto receive_error;
239
240	if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) {
241		*skb_push(skb, 1) = resp_hdr[1];
242		*skb_push(skb, 1) = resp_hdr[0];
243	}
244
245	return skb;
246
247receive_error:
248	kfree_skb(skb);
249
250	return NULL;
251}
252
253static int nci_spi_check_crc(struct sk_buff *skb)
254{
255	u16 crc_data = (skb->data[skb->len - 2] << 8) |
256			skb->data[skb->len - 1];
257	int ret;
258
259	ret = (crc_ccitt(CRC_INIT, skb->data, skb->len - NCI_SPI_CRC_LEN)
260			== crc_data);
261
262	skb_trim(skb, skb->len - NCI_SPI_CRC_LEN);
263
264	return ret;
265}
266
267static u8 nci_spi_get_ack(struct sk_buff *skb)
268{
269	u8 ret;
270
271	ret = skb->data[0] >> NCI_SPI_ACK_SHIFT;
272
273	/* Remove NFCC part of the header: ACK, NACK and MSB payload len */
274	skb_pull(skb, 2);
275
276	return ret;
277}
278
279/**
280 * nci_spi_read - read frame from NCI SPI drivers
281 *
282 * @nspi: The nci spi
283 * Context: can sleep
284 *
285 * This call may only be used from a context that may sleep.  The sleep
286 * is non-interruptible, and has no timeout.
287 *
288 * It returns an allocated skb containing the frame on success, or NULL.
289 */
290struct sk_buff *nci_spi_read(struct nci_spi *nspi)
291{
292	struct sk_buff *skb;
293
294	/* Retrieve frame from SPI */
295	skb = __nci_spi_read(nspi);
296	if (!skb)
297		goto done;
298
299	if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) {
300		if (!nci_spi_check_crc(skb)) {
301			send_acknowledge(nspi, ACKNOWLEDGE_NACK);
302			goto done;
303		}
304
305		/* In case of acknowledged mode: if ACK or NACK received,
306		 * unblock completion of latest frame sent.
307		 */
308		nspi->req_result = nci_spi_get_ack(skb);
309		if (nspi->req_result)
310			complete(&nspi->req_completion);
311	}
312
313	/* If there is no payload (ACK/NACK only frame),
314	 * free the socket buffer
315	 */
316	if (!skb->len) {
317		kfree_skb(skb);
318		skb = NULL;
319		goto done;
320	}
321
322	if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED)
323		send_acknowledge(nspi, ACKNOWLEDGE_ACK);
324
325done:
326
327	return skb;
328}
329EXPORT_SYMBOL_GPL(nci_spi_read);
330
331MODULE_LICENSE("GPL");