[PATCH v2 6/8] serial: Add Tegra Combined UART driver

Mikko Perttunen
2018-06-20T12:21:32Z

The Tegra Combined UART (TCU) is a mailbox-based mechanism that allows
multiplexing multiple "virtual UARTs" into a single hardware serial
port. The TCU is the primary serial port on Tegra194 devices.

Add a TCU driver utilizing the mailbox framework, as the used mailboxes
are part of Tegra HSP blocks that are already controlled by the Tegra
HSP mailbox driver.

Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
---

Notes:
v2:
- Removed (void) casts for unused variables.
- Changed the uart_set_options() call to be on one line, even if its
over 80 characters.
- Added defines for magic numbers.
- Style fixes.
- Changed Kconfig entry to depend on the Tegra HSP driver instead of
just the mailbox framework.

drivers/tty/serial/Kconfig | 9 ++
drivers/tty/serial/Makefile | 1 +
drivers/tty/serial/tegra-tcu.c | 289 +++++++++++++++++++++++++++++++++++++++
include/uapi/linux/serial_core.h | 3 +
4 files changed, 302 insertions(+)
create mode 100644 drivers/tty/serial/tegra-tcu.c

diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index df8bd0c7b97d..5fdd336e8937 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -322,6 +322,15 @@ config SERIAL_TEGRA
are enabled). This driver uses the APB DMA to achieve higher baudrate
and better performance.

+config SERIAL_TEGRA_TCU
+ tristate "NVIDIA Tegra Combined UART"
+ depends on ARCH_TEGRA && TEGRA_HSP_MBOX
+ select SERIAL_CORE
+ help
+ Support for the mailbox-based TCU (Tegra Combined UART) serial port.
+ TCU is a virtual serial port that allows multiplexing multiple data
+ streams into a single hardware serial port.
+
config SERIAL_MAX3100
tristate "MAX3100 support"
depends on SPI
diff --git a/drivers/tty/serial/Makefile b/drivers/tty/serial/Makefile
index daac675612df..4ad82231ff8a 100644
--- a/drivers/tty/serial/Makefile
+++ b/drivers/tty/serial/Makefile
@@ -76,6 +76,7 @@ obj-$(CONFIG_SERIAL_LANTIQ) += lantiq.o
obj-$(CONFIG_SERIAL_XILINX_PS_UART) += xilinx_uartps.o
obj-$(CONFIG_SERIAL_SIRFSOC) += sirfsoc_uart.o
obj-$(CONFIG_SERIAL_TEGRA) += serial-tegra.o
+obj-$(CONFIG_SERIAL_TEGRA_TCU) += tegra-tcu.o
obj-$(CONFIG_SERIAL_AR933X) += ar933x_uart.o
obj-$(CONFIG_SERIAL_EFM32_UART) += efm32-uart.o
obj-$(CONFIG_SERIAL_ARC) += arc_uart.o
diff --git a/drivers/tty/serial/tegra-tcu.c b/drivers/tty/serial/tegra-tcu.c
new file mode 100644
index 000000000000..b54ebe2ad917
--- /dev/null
+++ b/drivers/tty/serial/tegra-tcu.c
@@ -0,0 +1,289 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2018, NVIDIA CORPORATION. All rights reserved.
+ */
+
+#include <linux/console.h>
+#include <linux/mailbox_client.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/serial.h>
+#include <linux/serial_core.h>
+#include <linux/slab.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+
+#define TCU_MBOX_BYTE(i, x) ((x) << (i*8))
+#define TCU_MBOX_BYTE_V(x, i) (((x) >> (i*8)) & 0xff)
+#define TCU_MBOX_NUM_BYTES(x) ((x) << 24)
+#define TCU_MBOX_NUM_BYTES_V(x) (((x) >> 24) & 0x3)
+#define TCU_MBOX_FLUSH BIT(26)
+
+static struct uart_driver tegra_tcu_uart_driver;
+static struct uart_port tegra_tcu_uart_port;
+
+struct tegra_tcu {
+ struct mbox_client tx_client, rx_client;
+ struct mbox_chan *tx, *rx;
+};
+
+static unsigned int tegra_tcu_uart_tx_empty(struct uart_port *port)
+{
+ return TIOCSER_TEMT;
+}
+
+static void tegra_tcu_uart_set_mctrl(struct uart_port *port, unsigned int mctrl)
+{
+}
+
+static unsigned int tegra_tcu_uart_get_mctrl(struct uart_port *port)
+{
+ return 0;
+}
+
+static void tegra_tcu_uart_stop_tx(struct uart_port *port)
+{
+}
+
+static void tegra_tcu_write(const char *s, unsigned int count)
+{
+ struct tegra_tcu *tcu = tegra_tcu_uart_port.private_data;
+ unsigned int written = 0, i = 0;
+ bool insert_nl = false;
+ uint32_t value = 0;
+
+ while (i < count) {
+ if (insert_nl) {
+ value |= TCU_MBOX_BYTE(written++, '\n');
+ insert_nl = false;
+ i++;
+ } else if (s[i] == '\n') {
+ value |= TCU_MBOX_BYTE(written++, '\r');
+ insert_nl = true;
+ } else {
+ value |= TCU_MBOX_BYTE(written++, s[i++]);
+ }
+
+ if (written == 3) {
+ value |= TCU_MBOX_NUM_BYTES(3) | TCU_MBOX_FLUSH;
+ mbox_send_message(tcu->tx, &value);
+ value = 0;
+ written = 0;
+ }
+ }
+
+ if (written) {
+ value |= TCU_MBOX_NUM_BYTES(written) | TCU_MBOX_FLUSH;
+ mbox_send_message(tcu->tx, &value);
+ }
+}
+
+static void tegra_tcu_uart_start_tx(struct uart_port *port)
+{
+ struct circ_buf *xmit = &port->state->xmit;
+ unsigned long count;
+
+ for (;;) {
+ count = CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE);
+ if (!count)
+ break;
+
+ tegra_tcu_write(&xmit->buf[xmit->tail], count);
+ xmit->tail = (xmit->tail + count) & (UART_XMIT_SIZE - 1);
+ }
+
+ uart_write_wakeup(port);
+}
+
+static void tegra_tcu_uart_stop_rx(struct uart_port *port)
+{
+}
+
+static void tegra_tcu_uart_break_ctl(struct uart_port *port, int ctl)
+{
+}
+
+static int tegra_tcu_uart_startup(struct uart_port *port)
+{
+ return 0;
+}
+
+static void tegra_tcu_uart_shutdown(struct uart_port *port)
+{
+}
+
+static void tegra_tcu_uart_set_termios(struct uart_port *port,
+ struct ktermios *new,
+ struct ktermios *old)
+{
+}
+
+static const struct uart_ops tegra_tcu_uart_ops = {
+ .tx_empty = tegra_tcu_uart_tx_empty,
+ .set_mctrl = tegra_tcu_uart_set_mctrl,
+ .get_mctrl = tegra_tcu_uart_get_mctrl,
+ .stop_tx = tegra_tcu_uart_stop_tx,
+ .start_tx = tegra_tcu_uart_start_tx,
+ .stop_rx = tegra_tcu_uart_stop_rx,
+ .break_ctl = tegra_tcu_uart_break_ctl,
+ .startup = tegra_tcu_uart_startup,
+ .shutdown = tegra_tcu_uart_shutdown,
+ .set_termios = tegra_tcu_uart_set_termios,
+};
+
+static void tegra_tcu_console_write(struct console *cons, const char *s,
+ unsigned int count)
+{
+ tegra_tcu_write(s, count);
+}
+
+static int tegra_tcu_console_setup(struct console *cons, char *options)
+{
+ if (!tegra_tcu_uart_port.private_data)
+ return -ENODEV;
+
+ return uart_set_options(&tegra_tcu_uart_port, cons, 115200, 'n', 8, 'n');
+}
+
+static struct console tegra_tcu_console = {
+ .name = "ttyTCU",
+ .device = uart_console_device,
+ .flags = CON_PRINTBUFFER | CON_ANYTIME,
+ .index = -1,
+ .write = tegra_tcu_console_write,
+ .setup = tegra_tcu_console_setup,
+ .data = &tegra_tcu_uart_driver,
+};
+
+static struct uart_driver tegra_tcu_uart_driver = {
+ .owner = THIS_MODULE,
+ .driver_name = "tegra-tcu",
+ .dev_name = "ttyTCU",
+ .cons = &tegra_tcu_console,
+ .nr = 1,
+};
+
+static void tegra_tcu_receive(struct mbox_client *client, void *msg_p)
+{
+ struct tty_port *port = &tegra_tcu_uart_port.state->port;
+ uint32_t msg = *(uint32_t *)msg_p;
+ unsigned int num_bytes;
+ int i;
+
+ num_bytes = TCU_MBOX_NUM_BYTES_V(msg);
+ for (i = 0; i < num_bytes; i++)
+ tty_insert_flip_char(port, TCU_MBOX_BYTE_V(msg, i), TTY_NORMAL);
+
+ tty_flip_buffer_push(port);
+}
+
+static int tegra_tcu_probe(struct platform_device *pdev)
+{
+ struct uart_port *port = &tegra_tcu_uart_port;
+ struct tegra_tcu *tcu;
+ int err;
+
+ tcu = devm_kzalloc(&pdev->dev, sizeof(*tcu), GFP_KERNEL);
+ if (!tcu)
+ return -ENOMEM;
+
+ tcu->tx_client.dev = &pdev->dev;
+ tcu->rx_client.dev = &pdev->dev;
+ tcu->rx_client.rx_callback = tegra_tcu_receive;
+
+ tcu->tx = mbox_request_channel_byname(&tcu->tx_client, "tx");
+ if (IS_ERR(tcu->tx)) {
+ err = PTR_ERR(tcu->tx);
+ dev_err(&pdev->dev, "failed to get tx mailbox: %d\n", err);
+ return err;
+ }
+
+ tcu->rx = mbox_request_channel_byname(&tcu->rx_client, "rx");
+ if (IS_ERR(tcu->rx)) {
+ err = PTR_ERR(tcu->rx);
+ dev_err(&pdev->dev, "failed to get rx mailbox: %d\n", err);
+ goto free_tx;
+ }
+
+ err = uart_register_driver(&tegra_tcu_uart_driver);
+ if (err) {
+ dev_err(&pdev->dev, "failed to register UART driver: %d\n",
+ err);
+ goto free_rx;
+ }
+
+ spin_lock_init(&port->lock);
+ port->dev = &pdev->dev;
+ port->type = PORT_TEGRA_TCU;
+ port->ops = &tegra_tcu_uart_ops;
+ port->fifosize = 1;
+ port->iotype = UPIO_MEM;
+ port->flags = UPF_BOOT_AUTOCONF;
+ port->private_data = tcu;
+
+ err = uart_add_one_port(&tegra_tcu_uart_driver, port);
+ if (err) {
+ dev_err(&pdev->dev, "failed to add UART port: %d\n", err);
+ goto unregister_uart;
+ }
+
+ return 0;
+
+unregister_uart:
+ uart_unregister_driver(&tegra_tcu_uart_driver);
+free_rx:
+ mbox_free_channel(tcu->rx);
+free_tx:
+ mbox_free_channel(tcu->tx);
+
+ return err;
+}
+
+static int tegra_tcu_remove(struct platform_device *pdev)
+{
+ uart_remove_one_port(&tegra_tcu_uart_driver, &tegra_tcu_uart_port);
+ uart_unregister_driver(&tegra_tcu_uart_driver);
+
+ return 0;
+}
+
+static const struct of_device_id tegra_tcu_match[] = {
+ { .compatible = "nvidia,tegra194-tcu" },
+ { }
+};
+
+static struct platform_driver tegra_tcu_driver = {
+ .driver = {
+ .name = "tegra-tcu",
+ .of_match_table = tegra_tcu_match,
+ },
+ .probe = tegra_tcu_probe,
+ .remove = tegra_tcu_remove,
+};
+
+static int __init tegra_tcu_init(void)
+{
+ int err;
+
+ err = platform_driver_register(&tegra_tcu_driver);
+ if (err)
+ return err;
+
+ register_console(&tegra_tcu_console);
+
+ return 0;
+}
+module_init(tegra_tcu_init);
+
+static void __exit tegra_tcu_exit(void)
+{
+ unregister_console(&tegra_tcu_console);
+ platform_driver_unregister(&tegra_tcu_driver);
+}
+module_exit(tegra_tcu_exit);
+
+MODULE_AUTHOR("Mikko Perttunen <mperttunen@nvidia.com>");
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("NVIDIA Tegra Combined UART driver");
diff --git a/include/uapi/linux/serial_core.h b/include/uapi/linux/serial_core.h
index dce5f9dae121..69883c32cb98 100644
--- a/include/uapi/linux/serial_core.h
+++ b/include/uapi/linux/serial_core.h
@@ -79,6 +79,9 @@
/* Nuvoton UART */
#define PORT_NPCM 40

+/* NVIDIA Tegra Combined UART */
+#define PORT_TEGRA_TCU 41
+
/* Intel EG20 */
#define PORT_PCH_8LINE 44
#define PORT_PCH_2LINE 45
--
2.16.1