Message-ID: <20230902182845.1840620-3-ayushdevel1325@gmail.com>
Date:   Sat,  2 Sep 2023 23:58:42 +0530
From:   Ayush Singh <ayushdevel1325@...il.com>
To:     greybus-dev@...ts.linaro.org
Cc:     Ayush Singh <ayushdevel1325@...il.com>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org,
        Vaishnav M A <vaishnav@...gleboard.org>,
        Jason Kridner <jkridner@...gleboard.org>,
        Nishanth Menon <nm@...com>
Subject: [PATCH v4 2/3] greybus: Add BeaglePlay Linux Driver

Add the Greybus host driver for BeaglePlay board by BeagleBoard.org.

The current greybus setup involves running SVC in a user-space
application (GBridge) and using netlink to communicate with kernel
space. GBridge itself uses wpanusb kernel driver, so the greybus messages
travel from kernel space (gb_netlink) to user-space (GBridge) and then
back to kernel space (wpanusb) before reaching CC1352.

This driver directly communicates with CC1352 (running SVC Zephyr
application). Thus, it simplifies the complete greybus setup eliminating
user-space GBridge.

This driver is responsible for the following:
- Start SVC (CC1352) on driver load.
- Send/Receive Greybus messages to/from CC1352 using HDLC over UART.
- Print Logs from CC1352.
- Stop SVC (CC1352) on driver load.

Signed-off-by: Ayush Singh <ayushdevel1325@...il.com>
---
 MAINTAINERS                     |   1 +
 drivers/greybus/Kconfig         |  10 +
 drivers/greybus/Makefile        |   3 +-
 drivers/greybus/gb-beagleplay.c | 494 ++++++++++++++++++++++++++++++++
 4 files changed, 507 insertions(+), 1 deletion(-)
 create mode 100644 drivers/greybus/gb-beagleplay.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 9d1b49a6dfad..3cbf2c87fb14 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -8974,6 +8974,7 @@ M:	Ayush Singh <ayushdevel1325@...il.com>
 L:	greybus-dev@...ts.linaro.org (moderated for non-subscribers)
 S:	Maintained
 F:	Documentation/devicetree/bindings/serial/beaglecc1352.yaml
+F:	drivers/greybus/gb-beagleplay.c
 
 GREYBUS SUBSYSTEM
 M:	Johan Hovold <johan@...nel.org>
diff --git a/drivers/greybus/Kconfig b/drivers/greybus/Kconfig
index 78ba3c3083d5..62f091368272 100644
--- a/drivers/greybus/Kconfig
+++ b/drivers/greybus/Kconfig
@@ -28,5 +28,15 @@ config GREYBUS_ES2
 	  To compile this code as a module, choose M here: the module
 	  will be called gb-es2.ko
 
+config GREYBUS_BEAGLEPLAY
+	tristate "Greybus BeaglePlay driver"
+	depends on TTY
+	help
+	  Select this option if you have a BeaglePlay where CC1352
+		co-processor acts as Greybus SVC.
+
+	  To compile this code as a module, chose M here: the module
+	  will be called gb-beagleplay.ko
+
 endif	# GREYBUS
 
diff --git a/drivers/greybus/Makefile b/drivers/greybus/Makefile
index 9bccdd229aa2..63f9cb3b2df0 100644
--- a/drivers/greybus/Makefile
+++ b/drivers/greybus/Makefile
@@ -23,4 +23,5 @@ gb-es2-y := es2.o
 
 obj-$(CONFIG_GREYBUS_ES2)	+= gb-es2.o
 
-
+# Beagleplay Greybus driver
+obj-$(CONFIG_GREYBUS_BEAGLEPLAY)	+= gb-beagleplay.o
diff --git a/drivers/greybus/gb-beagleplay.c b/drivers/greybus/gb-beagleplay.c
new file mode 100644
index 000000000000..dccf30324203
--- /dev/null
+++ b/drivers/greybus/gb-beagleplay.c
@@ -0,0 +1,494 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Beagleplay Linux Driver for Greybus
+ *
+ * Copyright (c) 2023 Ayush Singh <ayushdevel1325@...il.com>
+ * Copyright (c) 2023  BeagleBoard.org Foundation
+ */
+
+#include <linux/gfp.h>
+#include <linux/greybus.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/printk.h>
+#include <linux/serdev.h>
+#include <linux/tty.h>
+#include <linux/tty_driver.h>
+#include <linux/greybus/hd.h>
+#include <linux/init.h>
+#include <linux/device.h>
+#include <linux/crc-ccitt.h>
+#include <linux/circ_buf.h>
+#include <linux/types.h>
+#include <linux/workqueue.h>
+
+#define RX_HDLC_PAYLOAD 1024
+#define CRC_LEN 2
+#define MAX_RX_HDLC (1 + RX_HDLC_PAYLOAD + CRC_LEN)
+#define TX_CIRC_BUF_SIZE 1024
+
+#define ADDRESS_GREYBUS 0x01
+#define ADDRESS_DBG 0x02
+#define ADDRESS_CONTROL 0x04
+
+#define HDLC_FRAME 0x7E
+#define HDLC_ESC 0x7D
+#define HDLC_XOR 0x20
+
+#define CONTROL_SVC_START 0x01
+#define CONTROL_SVC_STOP 0x02
+
+/* The maximum number of CPorts supported by Greybus Host Device */
+#define BEAGLEPLAY_GB_MAX_CPORTS 32
+
+static const struct of_device_id gb_beagleplay_of_match[] = {
+	{
+		.compatible = "beagle,cc1352",
+	},
+	{},
+};
+MODULE_DEVICE_TABLE(of, gb_beagleplay_of_match);
+
+/*
+ * BeaglePlay Greybus driver
+ *
+ * @serdev: Serdev device
+ *
+ * @gb_host_device: greybud host device
+ *
+ * @tx_work: transmit work
+ * @tx_producer_lock: transmit producer lock
+ * @tx_consumer_lock: transmit consumer lock
+ * @tx_circ_buf: transmit circular buffer
+ * @tx_crc: HDCL CRC
+ * @tx_ack_seq: current TX ACK sequence number
+ *
+ * @rx_buffer_len: Rx buffer length
+ * @rx_in_esc: Rx Flag to indicate if ESC
+ * @rx_buffer: Rx buffer
+ */
+struct gb_beagleplay {
+	struct serdev_device *serdev;
+
+	struct gb_host_device *gb_host_device;
+
+	struct work_struct tx_work;
+	/* tx_producer_lock: HDLC producer lock */
+	spinlock_t tx_producer_lock;
+	/* tx_consumer_lock: HDLC consumer lock */
+	spinlock_t tx_consumer_lock;
+	struct circ_buf tx_circ_buf;
+	u16 tx_crc;
+	u8 tx_ack_seq;
+
+	u16 rx_buffer_len;
+	u8 rx_in_esc;
+	u8 rx_buffer[MAX_RX_HDLC];
+};
+
+struct hdlc_payload {
+	u16 length;
+	void *payload;
+};
+
+static void hdlc_handle_greybus_frame(struct gb_beagleplay *bg, u8 *buffer,
+				      size_t buffer_len)
+{
+	u16 cport_id;
+	struct gb_operation_msg_hdr *hdr =
+		(struct gb_operation_msg_hdr *)buffer;
+
+	memcpy(&cport_id, hdr->pad, sizeof(cport_id));
+
+	dev_dbg(&bg->serdev->dev,
+		"Greybus Operation %u of Type %X on CPort %u with Status %u",
+		hdr->operation_id, hdr->type, cport_id, hdr->result);
+
+	greybus_data_rcvd(bg->gb_host_device, cport_id, buffer, buffer_len);
+}
+
+static void hdlc_handle_dbg_frame(struct gb_beagleplay *bg, const char *buffer,
+				  size_t buffer_len)
+{
+	dev_dbg(&bg->serdev->dev, "CC1352 Debug: %.*s", (int)buffer_len,
+		buffer);
+}
+
+/*
+ * Consume HDLC Buffer. This function assumes that consumer lock has been acquired.
+ */
+static void hdlc_write(struct gb_beagleplay *bg)
+{
+	/* Start consuning HDLC data */
+	int head = smp_load_acquire(&bg->tx_circ_buf.head);
+	int tail = bg->tx_circ_buf.tail;
+	int count = CIRC_CNT_TO_END(head, tail, TX_CIRC_BUF_SIZE);
+	const unsigned char *buf = &bg->tx_circ_buf.buf[tail];
+	int written;
+
+	if (count > 0) {
+		written = serdev_device_write_buf(bg->serdev, buf, count);
+
+		/* Finish consuming HDLC data */
+		smp_store_release(&bg->tx_circ_buf.tail,
+				  (tail + written) & (TX_CIRC_BUF_SIZE - 1));
+	}
+}
+
+/*
+ * Queue HDLC data for sending. This function assumes that producer lock as been acquired.
+ */
+static void hdlc_append(struct gb_beagleplay *bg, u8 value)
+{
+	int tail, head = bg->tx_circ_buf.head;
+
+	while (true) {
+		tail = READ_ONCE(bg->tx_circ_buf.tail);
+
+		if (CIRC_SPACE(head, tail, TX_CIRC_BUF_SIZE) >= 1) {
+			bg->tx_circ_buf.buf[head] = value;
+
+			/* Finish producing HDLC byte */
+			smp_store_release(&bg->tx_circ_buf.head,
+					  (head + 1) & (TX_CIRC_BUF_SIZE - 1));
+			return;
+		}
+		dev_warn(&bg->serdev->dev, "Tx circ buf full");
+		usleep_range(3000, 5000);
+	}
+}
+
+static void hdlc_append_escaped(struct gb_beagleplay *bg, u8 value)
+{
+	if (value == HDLC_FRAME || value == HDLC_ESC) {
+		hdlc_append(bg, HDLC_ESC);
+		value ^= HDLC_XOR;
+	}
+	hdlc_append(bg, value);
+}
+
+static void hdlc_append_tx_frame(struct gb_beagleplay *bg)
+{
+	bg->tx_crc = 0xFFFF;
+	hdlc_append(bg, HDLC_FRAME);
+}
+
+static void hdlc_append_tx_u8(struct gb_beagleplay *bg, u8 value)
+{
+	bg->tx_crc = crc_ccitt(bg->tx_crc, &value, 1);
+	hdlc_append_escaped(bg, value);
+}
+
+static void hdlc_append_tx_buffer(struct gb_beagleplay *bg, const u8 *buffer,
+				  size_t len)
+{
+	size_t i;
+
+	for (i = 0; i < len; i++)
+		hdlc_append_tx_u8(bg, buffer[i]);
+}
+
+static void hdlc_append_tx_crc(struct gb_beagleplay *bg)
+{
+	bg->tx_crc ^= 0xffff;
+	hdlc_append_escaped(bg, bg->tx_crc & 0xff);
+	hdlc_append_escaped(bg, (bg->tx_crc >> 8) & 0xff);
+}
+
+static void hdlc_handle_rx_frame(struct gb_beagleplay *bg)
+{
+	u8 address = bg->rx_buffer[0];
+	char *buffer = &bg->rx_buffer[2];
+	size_t buffer_len = bg->rx_buffer_len - 4;
+
+	switch (address) {
+	case ADDRESS_DBG:
+		hdlc_handle_dbg_frame(bg, buffer, buffer_len);
+		break;
+	case ADDRESS_GREYBUS:
+		hdlc_handle_greybus_frame(bg, buffer, buffer_len);
+		break;
+	default:
+		dev_warn(&bg->serdev->dev, "Got Unknown Frame %u", address);
+	}
+}
+
+static void hdlc_transmit(struct work_struct *work)
+{
+	struct gb_beagleplay *bg =
+		container_of(work, struct gb_beagleplay, tx_work);
+
+	spin_lock_bh(&bg->tx_consumer_lock);
+	hdlc_write(bg);
+	spin_unlock_bh(&bg->tx_consumer_lock);
+}
+
+static void hdlc_send_async(struct gb_beagleplay *bg, u8 address, u8 control,
+			    const struct hdlc_payload payloads[], size_t count)
+{
+	size_t i;
+
+	/* HDLC_FRAME
+	 * 0 address : 0x01
+	 * 1 control : 0x03
+	 * contents
+	 * x/y crc
+	 * HDLC_FRAME
+	 */
+
+	spin_lock(&bg->tx_producer_lock);
+
+	hdlc_append_tx_frame(bg);
+	hdlc_append_tx_u8(bg, address);
+	hdlc_append_tx_u8(bg, control);
+	for (i = 0; i < count; ++i) {
+		hdlc_append_tx_buffer(bg, payloads[i].payload,
+				      payloads[i].length);
+	}
+	hdlc_append_tx_crc(bg);
+	hdlc_append_tx_frame(bg);
+
+	spin_unlock(&bg->tx_producer_lock);
+
+	schedule_work(&bg->tx_work);
+}
+
+static void hdlc_send_s_frame_ack(struct gb_beagleplay *bg)
+{
+	hdlc_send_async(bg, bg->rx_buffer[0], (bg->rx_buffer[1] >> 1) & 0x7,
+			NULL, 0);
+}
+
+static int hdlc_rx(struct gb_beagleplay *bg, const u8 *data, size_t count)
+{
+	u16 crc_check;
+	size_t i;
+	u8 c, ctrl;
+
+	for (i = 0; i < count; ++i) {
+		c = data[i];
+
+		switch (c) {
+		case HDLC_FRAME:
+			if (bg->rx_buffer_len) {
+				crc_check = crc_ccitt(0xffff, bg->rx_buffer,
+						      bg->rx_buffer_len);
+				if (crc_check == 0xf0b8) {
+					ctrl = bg->rx_buffer[1];
+					if ((ctrl & 1) == 0) {
+						/* I-Frame, send S-Frame ACK */
+						hdlc_send_s_frame_ack(bg);
+					}
+					hdlc_handle_rx_frame(bg);
+				} else {
+					dev_err(&bg->serdev->dev,
+						"CRC Failed from %02x: 0x%04x",
+						bg->rx_buffer[0], crc_check);
+				}
+			}
+			bg->rx_buffer_len = 0;
+			break;
+		case HDLC_ESC:
+			bg->rx_in_esc = 1;
+			break;
+		default:
+			if (bg->rx_in_esc) {
+				c ^= 0x20;
+				bg->rx_in_esc = 0;
+			}
+
+			if (bg->rx_buffer_len < MAX_RX_HDLC) {
+				bg->rx_buffer[bg->rx_buffer_len] = c;
+				bg->rx_buffer_len++;
+			} else {
+				dev_err(&bg->serdev->dev, "RX Buffer Overflow");
+				bg->rx_buffer_len = 0;
+			}
+		}
+	}
+
+	return count;
+}
+
+static void hdlc_init(struct gb_beagleplay *bg)
+{
+	INIT_WORK(&bg->tx_work, hdlc_transmit);
+	spin_lock_init(&bg->tx_producer_lock);
+	spin_lock_init(&bg->tx_consumer_lock);
+	bg->tx_circ_buf.head = 0;
+	bg->tx_circ_buf.tail = 0;
+	bg->tx_circ_buf.buf =
+		devm_kmalloc(&bg->serdev->dev, TX_CIRC_BUF_SIZE, GFP_KERNEL);
+	bg->rx_buffer_len = 0;
+	bg->rx_in_esc = 0;
+}
+
+static void hdlc_deinit(struct gb_beagleplay *bg)
+{
+	flush_work(&bg->tx_work);
+}
+
+static int gb_beagleplay_tty_receive(struct serdev_device *serdev,
+				     const unsigned char *data, size_t count)
+{
+	struct gb_beagleplay *bg = serdev_device_get_drvdata(serdev);
+
+	return hdlc_rx(bg, data, count);
+}
+
+static void beagleplay_greybus_tty_wakeup(struct serdev_device *serdev)
+{
+	struct gb_beagleplay *bg = serdev_device_get_drvdata(serdev);
+
+	schedule_work(&bg->tx_work);
+}
+
+static struct serdev_device_ops gb_beagleplay_ops = {
+	.receive_buf = gb_beagleplay_tty_receive,
+	.write_wakeup = beagleplay_greybus_tty_wakeup,
+};
+
+static int gb_message_send(struct gb_host_device *hd, u16 cport_id,
+			   struct gb_message *msg, gfp_t gfp_mask)
+{
+	struct gb_beagleplay *bg = dev_get_drvdata(&hd->dev);
+	struct hdlc_payload payloads[2];
+
+	dev_dbg(&hd->dev,
+		"Sending Greybus message with Operation %u, Type: %X on Cport %u",
+		msg->header->operation_id, msg->header->type, cport_id);
+
+	if (msg->header->size > RX_HDLC_PAYLOAD) {
+		dev_err(&hd->dev, "Greybus message too big");
+		return -E2BIG;
+	}
+
+	memcpy(msg->header->pad, &cport_id, sizeof(cport_id));
+
+	payloads[0].payload = msg->header;
+	payloads[0].length = sizeof(*msg->header);
+	payloads[1].payload = msg->payload;
+	payloads[1].length = msg->payload_size;
+
+	hdlc_send_async(bg, ADDRESS_GREYBUS, 0x03, payloads, 2);
+	greybus_message_sent(bg->gb_host_device, msg, 0);
+
+	return 0;
+}
+
+static void gb_message_cancel(struct gb_message *message)
+{
+}
+
+static struct gb_hd_driver gb_hdlc_driver = { .message_send = gb_message_send,
+					      .message_cancel =
+						      gb_message_cancel };
+
+static void gb_beagleplay_start_svc(struct gb_beagleplay *bg)
+{
+	const u8 command = CONTROL_SVC_START;
+	const struct hdlc_payload payload = { .length = 1,
+					      .payload = (void *)&command };
+
+	hdlc_send_async(bg, ADDRESS_CONTROL, 0x03, &payload, 1);
+}
+
+static void gb_beagleplay_stop_svc(struct gb_beagleplay *bg)
+{
+	const u8 command = CONTROL_SVC_STOP;
+	const struct hdlc_payload payload = { .length = 1,
+					      .payload = (void *)&command };
+
+	hdlc_send_async(bg, ADDRESS_CONTROL, 0x03, &payload, 1);
+}
+
+static int gb_beagleplay_probe(struct serdev_device *serdev)
+{
+	u32 speed = 115200;
+	int ret = 0;
+	struct gb_beagleplay *bg =
+		devm_kmalloc(&serdev->dev, sizeof(*bg), GFP_KERNEL);
+
+	if (!bg) {
+		dev_err(&serdev->dev, "Failed to allocate driver");
+		return -ENOMEM;
+	}
+
+	bg->serdev = serdev;
+	serdev_device_set_drvdata(serdev, bg);
+	serdev_device_set_client_ops(serdev, &gb_beagleplay_ops);
+	ret = serdev_device_open(serdev);
+	if (ret) {
+		dev_err(&bg->serdev->dev, "Unable to Open Device");
+		return ret;
+	}
+	speed = serdev_device_set_baudrate(serdev, speed);
+	dev_info(&bg->serdev->dev, "Using baudrate %u", speed);
+	serdev_device_set_flow_control(serdev, false);
+
+	hdlc_init(bg);
+
+	/* Greybus setup */
+	bg->gb_host_device = gb_hd_create(&gb_hdlc_driver, &serdev->dev,
+					  TX_CIRC_BUF_SIZE,
+					  BEAGLEPLAY_GB_MAX_CPORTS);
+	if (IS_ERR(bg->gb_host_device)) {
+		dev_err(&bg->serdev->dev,
+			"Unable to create Greybus Host Device");
+		ret = -1;
+		goto free_hdlc;
+	}
+	ret = gb_hd_add(bg->gb_host_device);
+	if (ret) {
+		dev_err(&serdev->dev, "Failed to add Greybus Host Device");
+		goto free_gb_hd;
+	}
+	dev_set_drvdata(&bg->gb_host_device->dev, bg);
+
+	gb_beagleplay_start_svc(bg);
+
+	dev_info(&bg->serdev->dev, "Successful Beagleplay Greybus Probe");
+
+	return 0;
+
+free_gb_hd:
+	gb_hd_del(bg->gb_host_device);
+	gb_hd_put(bg->gb_host_device);
+free_hdlc:
+	hdlc_deinit(bg);
+	serdev_device_close(serdev);
+	return ret;
+}
+
+static void gb_beagleplay_remove(struct serdev_device *serdev)
+{
+	struct gb_beagleplay *beagleplay_greybus =
+		serdev_device_get_drvdata(serdev);
+
+	dev_info(&beagleplay_greybus->serdev->dev,
+		 "Remove BeaglePlay Greybus Driver");
+
+	gb_hd_del(beagleplay_greybus->gb_host_device);
+	gb_hd_put(beagleplay_greybus->gb_host_device);
+
+	gb_beagleplay_stop_svc(beagleplay_greybus);
+
+	hdlc_deinit(beagleplay_greybus);
+
+	serdev_device_close(serdev);
+}
+
+static struct serdev_device_driver gb_beagleplay_driver = {
+	.probe = gb_beagleplay_probe,
+	.remove = gb_beagleplay_remove,
+	.driver = {
+	      .name = "gb_beagleplay",
+	      .of_match_table = of_match_ptr(gb_beagleplay_of_match),
+	    },
+};
+
+module_serdev_device_driver(gb_beagleplay_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Ayush Singh <ayushdevel1325@...il.com>");
+MODULE_DESCRIPTION("A Greybus driver for BeaglePlay");
-- 
2.41.0

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