[PATCH v9 5/7] nfc: pn533: add UART phy driver

Lars Poeschel
2019-10-08T14:06:35Z

This adds the UART phy interface for the pn533 driver.
The pn533 driver can be used through UART interface this way.
It is implemented as a serdev device.

Cc: Johan Hovold <johan@kernel.org>
Cc: Claudiu Beznea <Claudiu.Beznea@microchip.com>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: Lars Poeschel <poeschel@lemonage.de>
---
Changes in v9:
- Rebased the patch series on v5.4-rc2

Changes in v8:
- Reverse christmas tree order for local variables in
pn532_uart_send_ack and pn532_uart_rx_is_frame

Changes in v7:
- Add comment at send_wakeup variable to document a possible and
harmless concurrency issue

Changes in v6:
- Rebased the patch series on v5.3-rc5

Changes in v5:
- Use the splitted pn53x_common_init and pn53x_register_nfc
and pn53x_common_clean and pn53x_unregister_nfc alike

Changes in v4:
- SPDX-License-Identifier: GPL-2.0+
- Source code comments above refering items
- Error check for serdev_device_write's
- Change if (xxx == NULL) to if (!xxx)
- Remove device name from a dev_err
- move pn533_register in _probe a bit towards the end of _probe
- make use of newly added dev_up / dev_down phy_ops
- control send_wakeup variable from dev_up / dev_down

Changes in v3:
- depend on SERIAL_DEV_BUS in Kconfig

Changes in v2:
- switched from tty line discipline to serdev, resulting in many
simplifications
- SPDX License Identifier

drivers/nfc/pn533/Kconfig | 11 ++
drivers/nfc/pn533/Makefile | 2 +
drivers/nfc/pn533/pn533.h | 8 +
drivers/nfc/pn533/uart.c | 324 +++++++++++++++++++++++++++++++++++++
4 files changed, 345 insertions(+)
create mode 100644 drivers/nfc/pn533/uart.c

diff --git a/drivers/nfc/pn533/Kconfig b/drivers/nfc/pn533/Kconfig
index f6d6b345ba0d..7fe1bbe26568 100644
--- a/drivers/nfc/pn533/Kconfig
+++ b/drivers/nfc/pn533/Kconfig
@@ -26,3 +26,14 @@ config NFC_PN533_I2C

If you choose to build a module, it'll be called pn533_i2c.
Say N if unsure.
+
+config NFC_PN532_UART
+ tristate "NFC PN532 device support (UART)"
+ depends on SERIAL_DEV_BUS
+ select NFC_PN533
+ ---help---
+ This module adds support for the NXP pn532 UART interface.
+ Select this if your platform is using the UART bus.
+
+ If you choose to build a module, it'll be called pn532_uart.
+ Say N if unsure.
diff --git a/drivers/nfc/pn533/Makefile b/drivers/nfc/pn533/Makefile
index 43c25b4f9466..b9648337576f 100644
--- a/drivers/nfc/pn533/Makefile
+++ b/drivers/nfc/pn533/Makefile
@@ -4,7 +4,9 @@
#
pn533_usb-objs = usb.o
pn533_i2c-objs = i2c.o
+pn532_uart-objs = uart.o

obj-$(CONFIG_NFC_PN533) += pn533.o
obj-$(CONFIG_NFC_PN533_USB) += pn533_usb.o
obj-$(CONFIG_NFC_PN533_I2C) += pn533_i2c.o
+obj-$(CONFIG_NFC_PN532_UART) += pn532_uart.o
diff --git a/drivers/nfc/pn533/pn533.h b/drivers/nfc/pn533/pn533.h
index 510ddebbd896..6541088fad73 100644
--- a/drivers/nfc/pn533/pn533.h
+++ b/drivers/nfc/pn533/pn533.h
@@ -43,6 +43,11 @@

/* Preamble (1), SoPC (2), ACK Code (2), Postamble (1) */
#define PN533_STD_FRAME_ACK_SIZE 6
+/*
+ * Preamble (1), SoPC (2), Packet Length (1), Packet Length Checksum (1),
+ * Specific Application Level Error Code (1) , Postamble (1)
+ */
+#define PN533_STD_ERROR_FRAME_SIZE 8
#define PN533_STD_FRAME_CHECKSUM(f) (f->data[f->datalen])
#define PN533_STD_FRAME_POSTAMBLE(f) (f->data[f->datalen + 1])
/* Half start code (3), LEN (4) should be 0xffff for extended frame */
@@ -84,6 +89,9 @@
#define PN533_CMD_MI_MASK 0x40
#define PN533_CMD_RET_SUCCESS 0x00

+#define PN533_FRAME_DATALEN_ACK 0x00
+#define PN533_FRAME_DATALEN_ERROR 0x01
+#define PN533_FRAME_DATALEN_EXTENDED 0xFF

enum pn533_protocol_type {
PN533_PROTO_REQ_ACK_RESP = 0,
diff --git a/drivers/nfc/pn533/uart.c b/drivers/nfc/pn533/uart.c
new file mode 100644
index 000000000000..7f639051cdd0
--- /dev/null
+++ b/drivers/nfc/pn533/uart.c
@@ -0,0 +1,324 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Driver for NXP PN532 NFC Chip - UART transport layer
+ *
+ * Copyright (C) 2018 Lemonage Software GmbH
+ * Author: Lars Pöschel <poeschel@lemonage.de>
+ * All rights reserved.
+ */
+
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/nfc.h>
+#include <linux/netdevice.h>
+#include <linux/of.h>
+#include <linux/serdev.h>
+#include "pn533.h"
+
+#define PN532_UART_SKB_BUFF_LEN (PN533_CMD_DATAEXCH_DATA_MAXLEN * 2)
+
+enum send_wakeup {
+ PN532_SEND_NO_WAKEUP = 0,
+ PN532_SEND_WAKEUP,
+ PN532_SEND_LAST_WAKEUP,
+};
+
+
+struct pn532_uart_phy {
+ struct serdev_device *serdev;
+ struct sk_buff *recv_skb;
+ struct pn533 *priv;
+ /*
+ * send_wakeup variable is used to control if we need to send a wakeup
+ * request to the pn532 chip prior to our actual command. There is a
+ * little propability of a race condition. We decided to not mutex the
+ * variable as the worst that could happen is, that we send a wakeup
+ * to the chip that is already awake. This does not hurt. It is a
+ * no-op to the chip.
+ */
+ enum send_wakeup send_wakeup;
+ struct timer_list cmd_timeout;
+ struct sk_buff *cur_out_buf;
+};
+
+static int pn532_uart_send_frame(struct pn533 *dev,
+ struct sk_buff *out)
+{
+ /* wakeup sequence and dummy bytes for waiting time */
+ static const u8 wakeup[] = {
+ 0x55, 0x55, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
+ struct pn532_uart_phy *pn532 = dev->phy;
+ int err;
+
+ print_hex_dump_debug("PN532_uart TX: ", DUMP_PREFIX_NONE, 16, 1,
+ out->data, out->len, false);
+
+ pn532->cur_out_buf = out;
+ if (pn532->send_wakeup) {
+ err= serdev_device_write(pn532->serdev,
+ wakeup, sizeof(wakeup),
+ MAX_SCHEDULE_TIMEOUT);
+ if (err < 0)
+ return err;
+ }
+
+ if (pn532->send_wakeup == PN532_SEND_LAST_WAKEUP) {
+ pn532->send_wakeup = PN532_SEND_NO_WAKEUP;
+ }
+
+ err = serdev_device_write(pn532->serdev, out->data, out->len,
+ MAX_SCHEDULE_TIMEOUT);
+ if (err < 0)
+ return err;
+
+ mod_timer(&pn532->cmd_timeout, HZ / 40 + jiffies);
+ return 0;
+}
+
+static int pn532_uart_send_ack(struct pn533 *dev, gfp_t flags)
+{
+ /* spec 7.1.1.3: Preamble, SoPC (2), ACK Code (2), Postamble */
+ static const u8 ack[PN533_STD_FRAME_ACK_SIZE] = {
+ 0x00, 0x00, 0xff, 0x00, 0xff, 0x00};
+ struct pn532_uart_phy *pn532 = dev->phy;
+ int err;
+
+ err = serdev_device_write(pn532->serdev, ack, sizeof(ack),
+ MAX_SCHEDULE_TIMEOUT);
+ if (err < 0)
+ return err;
+
+ return 0;
+}
+
+static void pn532_uart_abort_cmd(struct pn533 *dev, gfp_t flags)
+{
+ /* An ack will cancel the last issued command */
+ pn532_uart_send_ack(dev, flags);
+ /* schedule cmd_complete_work to finish current command execution */
+ pn533_recv_frame(dev, NULL, -ENOENT);
+}
+
+static void pn532_dev_up(struct pn533 *dev)
+{
+ struct pn532_uart_phy *pn532 = dev->phy;
+
+ serdev_device_open(pn532->serdev);
+ pn532->send_wakeup = PN532_SEND_LAST_WAKEUP;
+}
+
+static void pn532_dev_down(struct pn533 *dev)
+{
+ struct pn532_uart_phy *pn532 = dev->phy;
+
+ serdev_device_close(pn532->serdev);
+ pn532->send_wakeup = PN532_SEND_WAKEUP;
+}
+
+static struct pn533_phy_ops uart_phy_ops = {
+ .send_frame = pn532_uart_send_frame,
+ .send_ack = pn532_uart_send_ack,
+ .abort_cmd = pn532_uart_abort_cmd,
+ .dev_up = pn532_dev_up,
+ .dev_down = pn532_dev_down,
+};
+
+static void pn532_cmd_timeout(struct timer_list *t)
+{
+ struct pn532_uart_phy *dev = from_timer(dev, t, cmd_timeout);
+
+ pn532_uart_send_frame(dev->priv, dev->cur_out_buf);
+}
+
+/*
+ * scans the buffer if it contains a pn532 frame. It is not checked if the
+ * frame is really valid. This is later done with pn533_rx_frame_is_valid.
+ * This is useful for malformed or errornous transmitted frames. Adjusts the
+ * bufferposition where the frame starts, since pn533_recv_frame expects a
+ * well formed frame.
+ */
+static int pn532_uart_rx_is_frame(struct sk_buff *skb)
+{
+ struct pn533_std_frame *std;
+ struct pn533_ext_frame *ext;
+ u16 frame_len;
+ int i;
+
+ for (i = 0; i + PN533_STD_FRAME_ACK_SIZE <= skb->len; i++) {
+ std = (struct pn533_std_frame *)&skb->data[i];
+ /* search start code */
+ if (std->start_frame != cpu_to_be16(PN533_STD_FRAME_SOF))
+ continue;
+
+ /* frame type */
+ switch (std->datalen) {
+ case PN533_FRAME_DATALEN_ACK:
+ if (std->datalen_checksum == 0xff) {
+ skb_pull(skb, i);
+ return 1;
+ }
+
+ break;
+ case PN533_FRAME_DATALEN_ERROR:
+ if ((std->datalen_checksum == 0xff) &&
+ (skb->len >=
+ PN533_STD_ERROR_FRAME_SIZE)) {
+ skb_pull(skb, i);
+ return 1;
+ }
+
+ break;
+ case PN533_FRAME_DATALEN_EXTENDED:
+ ext = (struct pn533_ext_frame *)&skb->data[i];
+ frame_len = ext->datalen;
+ if (skb->len >= frame_len +
+ sizeof(struct pn533_ext_frame) +
+ 2 /* CKS + Postamble */) {
+ skb_pull(skb, i);
+ return 1;
+ }
+
+ break;
+ default: /* normal information frame */
+ frame_len = std->datalen;
+ if (skb->len >= frame_len +
+ sizeof(struct pn533_std_frame) +
+ 2 /* CKS + Postamble */) {
+ skb_pull(skb, i);
+ return 1;
+ }
+
+ break;
+ }
+ }
+
+ return 0;
+}
+
+static int pn532_receive_buf(struct serdev_device *serdev,
+ const unsigned char *data, size_t count)
+{
+ struct pn532_uart_phy *dev = serdev_device_get_drvdata(serdev);
+ size_t i;
+
+ del_timer(&dev->cmd_timeout);
+ for (i = 0; i < count; i++) {
+ skb_put_u8(dev->recv_skb, *data++);
+ if (!pn532_uart_rx_is_frame(dev->recv_skb))
+ continue;
+
+ pn533_recv_frame(dev->priv, dev->recv_skb, 0);
+ dev->recv_skb = alloc_skb(PN532_UART_SKB_BUFF_LEN, GFP_KERNEL);
+ if (!dev->recv_skb)
+ return 0;
+ }
+
+ return i;
+}
+
+static struct serdev_device_ops pn532_serdev_ops = {
+ .receive_buf = pn532_receive_buf,
+ .write_wakeup = serdev_device_write_wakeup,
+};
+
+static const struct of_device_id pn532_uart_of_match[] = {
+ { .compatible = "nxp,pn532", },
+ {},
+};
+MODULE_DEVICE_TABLE(of, pn532_uart_of_match);
+
+static int pn532_uart_probe(struct serdev_device *serdev)
+{
+ struct pn532_uart_phy *pn532;
+ struct pn533 *priv;
+ int err;
+
+ err = -ENOMEM;
+ pn532 = kzalloc(sizeof(*pn532), GFP_KERNEL);
+ if (!pn532)
+ goto err_exit;
+
+ pn532->recv_skb = alloc_skb(PN532_UART_SKB_BUFF_LEN, GFP_KERNEL);
+ if (!pn532->recv_skb)
+ goto err_free;
+
+ pn532->serdev = serdev;
+ serdev_device_set_drvdata(serdev, pn532);
+ serdev_device_set_client_ops(serdev, &pn532_serdev_ops);
+ err = serdev_device_open(serdev);
+ if (err) {
+ dev_err(&serdev->dev, "Unable to open device\n");
+ goto err_skb;
+ }
+
+ err = serdev_device_set_baudrate(serdev, 115200);
+ if (err != 115200) {
+ err = -EINVAL;
+ goto err_serdev;
+ }
+
+ serdev_device_set_flow_control(serdev, false);
+ pn532->send_wakeup = PN532_SEND_WAKEUP;
+ timer_setup(&pn532->cmd_timeout, pn532_cmd_timeout, 0);
+ priv = pn53x_common_init(PN533_DEVICE_PN532,
+ PN533_PROTO_REQ_ACK_RESP,
+ pn532, &uart_phy_ops, NULL,
+ &pn532->serdev->dev);
+ if (IS_ERR(priv)) {
+ err = PTR_ERR(priv);
+ goto err_serdev;
+ }
+
+ pn532->priv = priv;
+ err = pn533_finalize_setup(pn532->priv);
+ if (err)
+ goto err_clean;
+
+ serdev_device_close(serdev);
+ err = pn53x_register_nfc(priv, PN533_NO_TYPE_B_PROTOCOLS, &serdev->dev);
+ if (err) {
+ pn53x_common_clean(pn532->priv);
+ goto err_skb;
+ }
+
+ return err;
+
+err_clean:
+ pn53x_common_clean(pn532->priv);
+err_serdev:
+ serdev_device_close(serdev);
+err_skb:
+ kfree_skb(pn532->recv_skb);
+err_free:
+ kfree(pn532);
+err_exit:
+ return err;
+}
+
+static void pn532_uart_remove(struct serdev_device *serdev)
+{
+ struct pn532_uart_phy *pn532 = serdev_device_get_drvdata(serdev);
+
+ pn53x_unregister_nfc(pn532->priv);
+ serdev_device_close(serdev);
+ pn53x_common_clean(pn532->priv);
+ kfree_skb(pn532->recv_skb);
+ kfree(pn532);
+}
+
+static struct serdev_device_driver pn532_uart_driver = {
+ .probe = pn532_uart_probe,
+ .remove = pn532_uart_remove,
+ .driver = {
+ .name = "pn532_uart",
+ .of_match_table = of_match_ptr(pn532_uart_of_match),
+ },
+};
+
+module_serdev_device_driver(pn532_uart_driver);
+
+MODULE_AUTHOR("Lars Pöschel <poeschel@lemonage.de>");
+MODULE_DESCRIPTION("PN532 UART driver");
+MODULE_LICENSE("GPL");
--
2.23.0