cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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uart.c (8045B)


      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 = from_timer(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 int pn532_receive_buf(struct serdev_device *serdev,
    207		const unsigned char *data, size_t count)
    208{
    209	struct pn532_uart_phy *dev = serdev_device_get_drvdata(serdev);
    210	size_t i;
    211
    212	del_timer(&dev->cmd_timeout);
    213	for (i = 0; i < count; i++) {
    214		skb_put_u8(dev->recv_skb, *data++);
    215		if (!pn532_uart_rx_is_frame(dev->recv_skb))
    216			continue;
    217
    218		pn533_recv_frame(dev->priv, dev->recv_skb, 0);
    219		dev->recv_skb = alloc_skb(PN532_UART_SKB_BUFF_LEN, GFP_KERNEL);
    220		if (!dev->recv_skb)
    221			return 0;
    222	}
    223
    224	return i;
    225}
    226
    227static const struct serdev_device_ops pn532_serdev_ops = {
    228	.receive_buf = pn532_receive_buf,
    229	.write_wakeup = serdev_device_write_wakeup,
    230};
    231
    232static const struct of_device_id pn532_uart_of_match[] = {
    233	{ .compatible = "nxp,pn532", },
    234	{},
    235};
    236MODULE_DEVICE_TABLE(of, pn532_uart_of_match);
    237
    238static int pn532_uart_probe(struct serdev_device *serdev)
    239{
    240	struct pn532_uart_phy *pn532;
    241	struct pn533 *priv;
    242	int err;
    243
    244	err = -ENOMEM;
    245	pn532 = kzalloc(sizeof(*pn532), GFP_KERNEL);
    246	if (!pn532)
    247		goto err_exit;
    248
    249	pn532->recv_skb = alloc_skb(PN532_UART_SKB_BUFF_LEN, GFP_KERNEL);
    250	if (!pn532->recv_skb)
    251		goto err_free;
    252
    253	pn532->serdev = serdev;
    254	serdev_device_set_drvdata(serdev, pn532);
    255	serdev_device_set_client_ops(serdev, &pn532_serdev_ops);
    256	err = serdev_device_open(serdev);
    257	if (err) {
    258		dev_err(&serdev->dev, "Unable to open device\n");
    259		goto err_skb;
    260	}
    261
    262	err = serdev_device_set_baudrate(serdev, 115200);
    263	if (err != 115200) {
    264		err = -EINVAL;
    265		goto err_serdev;
    266	}
    267
    268	serdev_device_set_flow_control(serdev, false);
    269	pn532->send_wakeup = PN532_SEND_WAKEUP;
    270	timer_setup(&pn532->cmd_timeout, pn532_cmd_timeout, 0);
    271	priv = pn53x_common_init(PN533_DEVICE_PN532_AUTOPOLL,
    272				     PN533_PROTO_REQ_ACK_RESP,
    273				     pn532, &uart_phy_ops, NULL,
    274				     &pn532->serdev->dev);
    275	if (IS_ERR(priv)) {
    276		err = PTR_ERR(priv);
    277		goto err_serdev;
    278	}
    279
    280	pn532->priv = priv;
    281	err = pn533_finalize_setup(pn532->priv);
    282	if (err)
    283		goto err_clean;
    284
    285	serdev_device_close(serdev);
    286	err = pn53x_register_nfc(priv, PN533_NO_TYPE_B_PROTOCOLS, &serdev->dev);
    287	if (err) {
    288		pn53x_common_clean(pn532->priv);
    289		goto err_skb;
    290	}
    291
    292	return err;
    293
    294err_clean:
    295	pn53x_common_clean(pn532->priv);
    296err_serdev:
    297	serdev_device_close(serdev);
    298err_skb:
    299	kfree_skb(pn532->recv_skb);
    300err_free:
    301	kfree(pn532);
    302err_exit:
    303	return err;
    304}
    305
    306static void pn532_uart_remove(struct serdev_device *serdev)
    307{
    308	struct pn532_uart_phy *pn532 = serdev_device_get_drvdata(serdev);
    309
    310	pn53x_unregister_nfc(pn532->priv);
    311	serdev_device_close(serdev);
    312	pn53x_common_clean(pn532->priv);
    313	kfree_skb(pn532->recv_skb);
    314	kfree(pn532);
    315}
    316
    317static struct serdev_device_driver pn532_uart_driver = {
    318	.probe = pn532_uart_probe,
    319	.remove = pn532_uart_remove,
    320	.driver = {
    321		.name = "pn532_uart",
    322		.of_match_table = pn532_uart_of_match,
    323	},
    324};
    325
    326module_serdev_device_driver(pn532_uart_driver);
    327
    328MODULE_AUTHOR("Lars Pöschel <poeschel@lemonage.de>");
    329MODULE_DESCRIPTION("PN532 UART driver");
    330MODULE_LICENSE("GPL");