[v3,6/8] serial: Add Tegra Combined UART driver

Message ID 20180702114033.15654-7-mperttunen@nvidia.com
State New
Headers show
Series
  • Tegra Combined UART driver
Related show

Commit Message

Mikko Perttunen July 2, 2018, 11:40 a.m.
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.
    
    v3:
    - Removed FLUSH bit, as it's unnecessary and slows down printing
    - Removed call to uart_set_options
    - Added mbox_free_channel calls to remove()

 drivers/tty/serial/Kconfig       |   9 ++
 drivers/tty/serial/Makefile      |   1 +
 drivers/tty/serial/tegra-tcu.c   | 291 +++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/serial_core.h |   3 +
 4 files changed, 304 insertions(+)
 create mode 100644 drivers/tty/serial/tegra-tcu.c

Comments

Thierry Reding July 2, 2018, 1:18 p.m. | #1
On Mon, Jul 02, 2018 at 02:40:31PM +0300, Mikko Perttunen wrote:
> 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.
>     
>     v3:
>     - Removed FLUSH bit, as it's unnecessary and slows down printing
>     - Removed call to uart_set_options
>     - Added mbox_free_channel calls to remove()
> 
>  drivers/tty/serial/Kconfig       |   9 ++
>  drivers/tty/serial/Makefile      |   1 +
>  drivers/tty/serial/tegra-tcu.c   | 291 +++++++++++++++++++++++++++++++++++++++
>  include/uapi/linux/serial_core.h |   3 +
>  4 files changed, 304 insertions(+)
>  create mode 100644 drivers/tty/serial/tegra-tcu.c

The driver looks good to me. But for my own understanding, is there some
way we can make use of the multiplexing? That is, could we add a
mechanism to have the driver filter out only a specific stream? Could we
also specify which stream to send data back to? What happens by default?
Which stream is data sent to?

Thierry
Mikko Perttunen July 2, 2018, 1:30 p.m. | #2
On 02.07.2018 16:18, Thierry Reding wrote:
> On Mon, Jul 02, 2018 at 02:40:31PM +0300, Mikko Perttunen wrote:
>> 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.
>>      
>>      v3:
>>      - Removed FLUSH bit, as it's unnecessary and slows down printing
>>      - Removed call to uart_set_options
>>      - Added mbox_free_channel calls to remove()
>>
>>   drivers/tty/serial/Kconfig       |   9 ++
>>   drivers/tty/serial/Makefile      |   1 +
>>   drivers/tty/serial/tegra-tcu.c   | 291 +++++++++++++++++++++++++++++++++++++++
>>   include/uapi/linux/serial_core.h |   3 +
>>   4 files changed, 304 insertions(+)
>>   create mode 100644 drivers/tty/serial/tegra-tcu.c
> 
> The driver looks good to me. But for my own understanding, is there some
> way we can make use of the multiplexing? That is, could we add a
> mechanism to have the driver filter out only a specific stream? Could we
> also specify which stream to send data back to? What happens by default?
> Which stream is data sent to?

There is no multiplexing on the producer/device side (i.e. what this 
driver does). The mailbox specified in device tree specifies the stream 
we send stuff to. The mailboxes are per-CPU (we use the CCPLEX mailbox 
here), so it cannot really be changed.

The consumer then sees the multiplexing in that it can receive from and 
transmit to all of the various CPUs in the system at the same time. AIUI 
there is also a secondary form of multiplexing where the outputs of 
different VMs can be multiplexed by the hypervisor, but I'm not very 
familiar with that.

Mikko

> 
> Thierry
> 
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Thierry Reding July 2, 2018, 1:47 p.m. | #3
On Mon, Jul 02, 2018 at 04:30:07PM +0300, Mikko Perttunen wrote:
> On 02.07.2018 16:18, Thierry Reding wrote:
> > On Mon, Jul 02, 2018 at 02:40:31PM +0300, Mikko Perttunen wrote:
> > > 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.
> > >      v3:
> > >      - Removed FLUSH bit, as it's unnecessary and slows down printing
> > >      - Removed call to uart_set_options
> > >      - Added mbox_free_channel calls to remove()
> > > 
> > >   drivers/tty/serial/Kconfig       |   9 ++
> > >   drivers/tty/serial/Makefile      |   1 +
> > >   drivers/tty/serial/tegra-tcu.c   | 291 +++++++++++++++++++++++++++++++++++++++
> > >   include/uapi/linux/serial_core.h |   3 +
> > >   4 files changed, 304 insertions(+)
> > >   create mode 100644 drivers/tty/serial/tegra-tcu.c
> > 
> > The driver looks good to me. But for my own understanding, is there some
> > way we can make use of the multiplexing? That is, could we add a
> > mechanism to have the driver filter out only a specific stream? Could we
> > also specify which stream to send data back to? What happens by default?
> > Which stream is data sent to?
> 
> There is no multiplexing on the producer/device side (i.e. what this driver
> does). The mailbox specified in device tree specifies the stream we send
> stuff to. The mailboxes are per-CPU (we use the CCPLEX mailbox here), so it
> cannot really be changed.

Oh, I see, so there is one stream per pair of mailboxes? That is, the
mailboxes we specify in the DT define which stream we receive from and
send to?

Thierry
Mikko Perttunen July 3, 2018, 6:40 a.m. | #4
On 02.07.2018 16:47, Thierry Reding wrote:
> On Mon, Jul 02, 2018 at 04:30:07PM +0300, Mikko Perttunen wrote:
>> On 02.07.2018 16:18, Thierry Reding wrote:
>>> On Mon, Jul 02, 2018 at 02:40:31PM +0300, Mikko Perttunen wrote:
>>>> 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.
>>>>       v3:
>>>>       - Removed FLUSH bit, as it's unnecessary and slows down printing
>>>>       - Removed call to uart_set_options
>>>>       - Added mbox_free_channel calls to remove()
>>>>
>>>>    drivers/tty/serial/Kconfig       |   9 ++
>>>>    drivers/tty/serial/Makefile      |   1 +
>>>>    drivers/tty/serial/tegra-tcu.c   | 291 +++++++++++++++++++++++++++++++++++++++
>>>>    include/uapi/linux/serial_core.h |   3 +
>>>>    4 files changed, 304 insertions(+)
>>>>    create mode 100644 drivers/tty/serial/tegra-tcu.c
>>>
>>> The driver looks good to me. But for my own understanding, is there some
>>> way we can make use of the multiplexing? That is, could we add a
>>> mechanism to have the driver filter out only a specific stream? Could we
>>> also specify which stream to send data back to? What happens by default?
>>> Which stream is data sent to?
>>
>> There is no multiplexing on the producer/device side (i.e. what this driver
>> does). The mailbox specified in device tree specifies the stream we send
>> stuff to. The mailboxes are per-CPU (we use the CCPLEX mailbox here), so it
>> cannot really be changed.
> 
> Oh, I see, so there is one stream per pair of mailboxes? That is, the
> mailboxes we specify in the DT define which stream we receive from and
> send to?

Correct.

Mikko

> 
> Thierry
> 
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Patch

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..de58815bb215
--- /dev/null
+++ b/drivers/tty/serial/tegra-tcu.c
@@ -0,0 +1,291 @@ 
+// 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)
+
+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);
+			mbox_send_message(tcu->tx, &value);
+			value = 0;
+			written = 0;
+		}
+	}
+
+	if (written) {
+		value |= TCU_MBOX_NUM_BYTES(written);
+		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)
+{
+	return 0;
+}
+
+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;
+	}
+
+	platform_set_drvdata(pdev, tcu);
+
+	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)
+{
+	struct tegra_tcu *tcu = platform_get_drvdata(pdev);
+
+	uart_remove_one_port(&tegra_tcu_uart_driver, &tegra_tcu_uart_port);
+	uart_unregister_driver(&tegra_tcu_uart_driver);
+	mbox_free_channel(tcu->rx);
+	mbox_free_channel(tcu->tx);
+
+	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