Re: [PATCH v6 5/5] drivers/tty/serial: add LiteUART driver

Mateusz Holenko
2020-06-04T07:16:40Z

On Wed, May 27, 2020 at 6:27 PM Mateusz Holenko <mholenko@antmicro.com> wrote:
>
> From: Filip Kokosinski <fkokosinski@antmicro.com>
>
> This commit adds driver for the FPGA-based LiteUART serial controller
> from LiteX SoC builder.
>
> The current implementation supports LiteUART configured
> for 32 bit data width and 8 bit CSR bus width.
>
> It does not support IRQ.
>
> Signed-off-by: Filip Kokosinski <fkokosinski@antmicro.com>
> Signed-off-by: Mateusz Holenko <mholenko@antmicro.com>
> ---
>
> Notes:
> Changes in v6:
> - LiteUART ports now stored in xArray
> - removed PORT_LITEUART
> - fixed formatting
> - removed some unnecessary defines
>
> No changes in v5.
>
> Changes in v4:
> - fixed copyright header
> - removed a wrong dependency on UARTLITE from Kconfig
> - added a dependency on LITEX_SOC_CONTROLLER to LITEUART in Kconfig
>
> Changes in v3:
> - aliases made optional
> - used litex_get_reg/litex_set_reg functions instead of macros
> - SERIAL_LITEUART_NR_PORTS renamed to SERIAL_LITEUART_MAX_PORTS
> - PORT_LITEUART changed from 122 to 123
> - added dependency on LITEX_SOC_CONTROLLER
> - patch number changed from 4 to 5
>
> No changes in v2.
>
> MAINTAINERS | 1 +
> drivers/tty/serial/Kconfig | 31 +++
> drivers/tty/serial/Makefile | 1 +
> drivers/tty/serial/liteuart.c | 404 ++++++++++++++++++++++++++++++++++
> 4 files changed, 437 insertions(+)
> create mode 100644 drivers/tty/serial/liteuart.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 51d2d6a61fb0..d855fe807833 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -9846,6 +9846,7 @@ M: Mateusz Holenko <mholenko@antmicro.com>
> S: Maintained
> F: Documentation/devicetree/bindings/*/litex,*.yaml
> F: drivers/soc/litex/litex_soc_ctrl.c
> +F: drivers/tty/serial/liteuart.c
> F: include/linux/litex.h
>
> LIVE PATCHING
> diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
> index adf9e80e7dc9..17aaf0afb27a 100644
> --- a/drivers/tty/serial/Kconfig
> +++ b/drivers/tty/serial/Kconfig
> @@ -1562,6 +1562,37 @@ config SERIAL_MILBEAUT_USIO_CONSOLE
> receives all kernel messages and warnings and which allows logins in
> single user mode).
>
> +config SERIAL_LITEUART
> + tristate "LiteUART serial port support"
> + depends on HAS_IOMEM
> + depends on OF || COMPILE_TEST
> + depends on LITEX_SOC_CONTROLLER
> + select SERIAL_CORE
> + help
> + This driver is for the FPGA-based LiteUART serial controller from LiteX
> + SoC builder.
> +
> + Say 'Y' here if you wish to use the LiteUART serial controller.
> + Otherwise, say 'N'.
> +
> +config SERIAL_LITEUART_MAX_PORTS
> + int "Maximum number of LiteUART ports"
> + depends on SERIAL_LITEUART
> + default "1"
> + help
> + Set this to the maximum number of serial ports you want the driver
> + to support.
> +
> +config SERIAL_LITEUART_CONSOLE
> + bool "LiteUART serial port console support"
> + depends on SERIAL_LITEUART=y
> + select SERIAL_CORE_CONSOLE
> + help
> + Say 'Y' here if you wish to use the FPGA-based LiteUART serial controller
> + from LiteX SoC builder as the system console (the system console is the
> + device which receives all kernel messages and warnings and which allows
> + logins in single user mode). Otherwise, say 'N'.
> +
> endmenu
>
> config SERIAL_MCTRL_GPIO
> diff --git a/drivers/tty/serial/Makefile b/drivers/tty/serial/Makefile
> index d056ee6cca33..9f8ba419ff3b 100644
> --- a/drivers/tty/serial/Makefile
> +++ b/drivers/tty/serial/Makefile
> @@ -89,6 +89,7 @@ obj-$(CONFIG_SERIAL_OWL) += owl-uart.o
> obj-$(CONFIG_SERIAL_RDA) += rda-uart.o
> obj-$(CONFIG_SERIAL_MILBEAUT_USIO) += milbeaut_usio.o
> obj-$(CONFIG_SERIAL_SIFIVE) += sifive.o
> +obj-$(CONFIG_SERIAL_LITEUART) += liteuart.o
>
> # GPIOLIB helpers for modem control lines
> obj-$(CONFIG_SERIAL_MCTRL_GPIO) += serial_mctrl_gpio.o
> diff --git a/drivers/tty/serial/liteuart.c b/drivers/tty/serial/liteuart.c
> new file mode 100644
> index 000000000000..22b7612c13ca
> --- /dev/null
> +++ b/drivers/tty/serial/liteuart.c
> @@ -0,0 +1,404 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * LiteUART serial controller (LiteX) Driver
> + *
> + * Copyright (C) 2019-2020 Antmicro <www.antmicro.com>
> + */
> +
> +#include <linux/console.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/of_platform.h>
> +#include <linux/serial.h>
> +#include <linux/serial_core.h>
> +#include <linux/timer.h>
> +#include <linux/tty_flip.h>
> +#include <linux/litex.h>
> +#include <linux/xarray.h>

kbuild test robot reported problems with this patch, namely: implicit
declaration of function 'kzalloc'
This is caused by the missing include directive. When I was testing it
I must have missed the warning, but the compilation succeeded and the
resulting binary worked fine on HW (LiteX/mor1kx platform).
The fix is a simple one-liner, adding a new include:

+#include <linux/slab.h>

Since this is a very small fix and does not modify the actual code of
the driver I want to wait for more feedback on all patches in the
series before resubmitting, in order to limit traffic on the list.
Or should I generate the next version and resend the whole patchset
with this single fix, as otherwise it won't be reviewed at all?

> +
> +/*
> + * CSRs definitions (base address offsets + width)
> + *
> + * The definitions below are true for LiteX SoC configured for 8-bit CSR Bus,
> + * 32-bit aligned.
> + *
> + * Supporting other configurations might require new definitions or a more
> + * generic way of indexing the LiteX CSRs.
> + *
> + * For more details on how CSRs are defined and handled in LiteX, see comments
> + * in the LiteX SoC Driver: drivers/soc/litex/litex_soc_ctrl.c
> + */
> +#define OFF_RXTX 0x00
> +#define OFF_TXFULL 0x04
> +#define OFF_RXEMPTY 0x08
> +#define OFF_EV_STATUS 0x0c
> +#define OFF_EV_PENDING 0x10
> +#define OFF_EV_ENABLE 0x14
> +
> +/* events */
> +#define EV_TX 0x1
> +#define EV_RX 0x2
> +
> +struct liteuart_port {
> + struct uart_port port;
> + struct timer_list timer;
> +};
> +
> +#define to_liteuart_port(port) container_of(port, struct liteuart_port, port)
> +
> +static DEFINE_XARRAY_FLAGS(liteuart_array, XA_FLAGS_ALLOC);
> +
> +#ifdef CONFIG_SERIAL_LITEUART_CONSOLE
> +static struct console liteuart_console;
> +#endif
> +
> +static struct uart_driver liteuart_driver = {
> + .owner = THIS_MODULE,
> + .driver_name = "liteuart",
> + .dev_name = "ttyLXU",
> + .major = 0,
> + .minor = 0,
> + .nr = CONFIG_SERIAL_LITEUART_MAX_PORTS,
> +#ifdef CONFIG_SERIAL_LITEUART_CONSOLE
> + .cons = &liteuart_console,
> +#endif
> +};
> +
> +static void liteuart_timer(struct timer_list *t)
> +{
> + struct liteuart_port *uart = from_timer(uart, t, timer);
> + struct uart_port *port = &uart->port;
> + unsigned char __iomem *membase = port->membase;
> + unsigned int flg = TTY_NORMAL;
> + int ch;
> + unsigned long status;
> +
> + while ((status = !litex_get_reg(membase + OFF_RXEMPTY, 1)) == 1) {
> + ch = litex_get_reg(membase + OFF_RXTX, 1);
> + port->icount.rx++;
> +
> + /* necessary for RXEMPTY to refresh its value */
> + litex_set_reg(membase + OFF_EV_PENDING, 1, EV_TX | EV_RX);
> +
> + /* no overflow bits in status */
> + if (!(uart_handle_sysrq_char(port, ch)))
> + uart_insert_char(port, status, 0, ch, flg);
> +
> + tty_flip_buffer_push(&port->state->port);
> + }
> +
> + mod_timer(&uart->timer, jiffies + uart_poll_timeout(port));
> +}
> +
> +static void liteuart_putchar(struct uart_port *port, int ch)
> +{
> + while (litex_get_reg(port->membase + OFF_TXFULL, 1))
> + cpu_relax();
> +
> + litex_set_reg(port->membase + OFF_RXTX, 1, ch);
> +}
> +
> +static unsigned int liteuart_tx_empty(struct uart_port *port)
> +{
> + /* not really tx empty, just checking if tx is not full */
> + if (!litex_get_reg(port->membase + OFF_TXFULL, 1))
> + return TIOCSER_TEMT;
> +
> + return 0;
> +}
> +
> +static void liteuart_set_mctrl(struct uart_port *port, unsigned int mctrl)
> +{
> + /* modem control register is not present in LiteUART */
> +}
> +
> +static unsigned int liteuart_get_mctrl(struct uart_port *port)
> +{
> + return TIOCM_CTS | TIOCM_DSR | TIOCM_CAR;
> +}
> +
> +static void liteuart_stop_tx(struct uart_port *port)
> +{
> +}
> +
> +static void liteuart_start_tx(struct uart_port *port)
> +{
> + struct circ_buf *xmit = &port->state->xmit;
> + unsigned char ch;
> +
> + if (unlikely(port->x_char)) {
> + litex_set_reg(port->membase + OFF_RXTX, 1, port->x_char);
> + port->icount.tx++;
> + port->x_char = 0;
> + } else if (!uart_circ_empty(xmit)) {
> + while (xmit->head != xmit->tail) {
> + ch = xmit->buf[xmit->tail];
> + xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
> + port->icount.tx++;
> + liteuart_putchar(port, ch);
> + }
> + }
> +
> + if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
> + uart_write_wakeup(port);
> +}
> +
> +static void liteuart_stop_rx(struct uart_port *port)
> +{
> + struct liteuart_port *uart = to_liteuart_port(port);
> +
> + /* just delete timer */
> + del_timer(&uart->timer);
> +}
> +
> +static void liteuart_break_ctl(struct uart_port *port, int break_state)
> +{
> + /* LiteUART doesn't support sending break signal */
> +}
> +
> +static int liteuart_startup(struct uart_port *port)
> +{
> + struct liteuart_port *uart = to_liteuart_port(port);
> +
> + /* disable events */
> + litex_set_reg(port->membase + OFF_EV_ENABLE, 1, 0);
> +
> + /* prepare timer for polling */
> + timer_setup(&uart->timer, liteuart_timer, 0);
> + mod_timer(&uart->timer, jiffies + uart_poll_timeout(port));
> +
> + return 0;
> +}
> +
> +static void liteuart_shutdown(struct uart_port *port)
> +{
> +}
> +
> +static void liteuart_set_termios(struct uart_port *port, struct ktermios *new,
> + struct ktermios *old)
> +{
> + unsigned int baud;
> + unsigned long flags;
> +
> + spin_lock_irqsave(&port->lock, flags);
> +
> + /* update baudrate */
> + baud = uart_get_baud_rate(port, new, old, 0, 460800);
> + uart_update_timeout(port, new->c_cflag, baud);
> +
> + spin_unlock_irqrestore(&port->lock, flags);
> +}
> +
> +static const char *liteuart_type(struct uart_port *port)
> +{
> + return "liteuart";
> +}
> +
> +static void liteuart_release_port(struct uart_port *port)
> +{
> +}
> +
> +static int liteuart_request_port(struct uart_port *port)
> +{
> + return 0;
> +}
> +
> +static void liteuart_config_port(struct uart_port *port, int flags)
> +{
> + /*
> + * Driver core for serial ports forces a non-zero value for port type.
> + * Write an arbitrary value here to accommodate the serial core driver,
> + * as ID part of UAPI is redundant.
> + */
> + port->type = 1;
> +}
> +
> +static int liteuart_verify_port(struct uart_port *port,
> + struct serial_struct *ser)
> +{
> + if (port->type != PORT_UNKNOWN && ser->type != 1)
> + return -EINVAL;
> +
> + return 0;
> +}
> +
> +static const struct uart_ops liteuart_ops = {
> + .tx_empty = liteuart_tx_empty,
> + .set_mctrl = liteuart_set_mctrl,
> + .get_mctrl = liteuart_get_mctrl,
> + .stop_tx = liteuart_stop_tx,
> + .start_tx = liteuart_start_tx,
> + .stop_rx = liteuart_stop_rx,
> + .break_ctl = liteuart_break_ctl,
> + .startup = liteuart_startup,
> + .shutdown = liteuart_shutdown,
> + .set_termios = liteuart_set_termios,
> + .type = liteuart_type,
> + .release_port = liteuart_release_port,
> + .request_port = liteuart_request_port,
> + .config_port = liteuart_config_port,
> + .verify_port = liteuart_verify_port,
> +};
> +
> +static int liteuart_probe(struct platform_device *pdev)
> +{
> + struct device_node *np = pdev->dev.of_node;
> + struct liteuart_port *uart;
> + struct uart_port *port;
> + struct xa_limit limit;
> + int dev_id, ret;
> +
> + /* no device tree */
> + if (!np)
> + return -ENODEV;
> +
> + if (!litex_check_accessors())
> + return -EPROBE_DEFER;
> +
> + /* look for aliases; auto-enumerate for free index if not found */
> + dev_id = of_alias_get_id(np, "serial");
> + if (dev_id < 0)
> + limit = XA_LIMIT(0, CONFIG_SERIAL_LITEUART_MAX_PORTS);
> + else
> + limit = XA_LIMIT(dev_id, dev_id);
> +
> + uart = kzalloc(sizeof(struct liteuart_port), GFP_KERNEL);
> + if (!uart)
> + return -ENOMEM;
> +
> + ret = xa_alloc(&liteuart_array, &dev_id, uart, limit, GFP_KERNEL);
> + if (ret)
> + return ret;
> +
> + port = &uart->port;
> +
> + /* get membase */
> + port->membase = devm_platform_get_and_ioremap_resource(pdev, 0, NULL);
> + if (!port->membase)
> + return -ENXIO;
> +
> + /* values not from device tree */
> + port->dev = &pdev->dev;
> + port->iotype = UPIO_MEM;
> + port->flags = UPF_BOOT_AUTOCONF;
> + port->ops = &liteuart_ops;
> + port->regshift = 2;
> + port->fifosize = 16;
> + port->iobase = 1;
> + port->type = PORT_UNKNOWN;
> + port->line = dev_id;
> + spin_lock_init(&port->lock);
> +
> + return uart_add_one_port(&liteuart_driver, &uart->port);
> +}
> +
> +static int liteuart_remove(struct platform_device *pdev)
> +{
> + return 0;
> +}
> +
> +static const struct of_device_id liteuart_of_match[] = {
> + { .compatible = "litex,liteuart" },
> + {}
> +};
> +MODULE_DEVICE_TABLE(of, liteuart_of_match);
> +
> +static struct platform_driver liteuart_platform_driver = {
> + .probe = liteuart_probe,
> + .remove = liteuart_remove,
> + .driver = {
> + .name = "liteuart",
> + .of_match_table = liteuart_of_match,
> + },
> +};
> +
> +#ifdef CONFIG_SERIAL_LITEUART_CONSOLE
> +
> +static void liteuart_console_write(struct console *co, const char *s,
> + unsigned int count)
> +{
> + struct liteuart_port *uart;
> + struct uart_port *port;
> + unsigned long flags;
> +
> + uart = (struct liteuart_port *)xa_load(&liteuart_array, co->index);
> + port = &uart->port;
> +
> + spin_lock_irqsave(&port->lock, flags);
> + uart_console_write(port, s, count, liteuart_putchar);
> + spin_unlock_irqrestore(&port->lock, flags);
> +}
> +
> +static int liteuart_console_setup(struct console *co, char *options)
> +{
> + struct liteuart_port *uart;
> + struct uart_port *port;
> + int baud = 115200;
> + int bits = 8;
> + int parity = 'n';
> + int flow = 'n';
> +
> + uart = (struct liteuart_port *)xa_load(&liteuart_array, co->index);
> + if (!uart)
> + return -ENODEV;
> +
> + port = &uart->port;
> + if (!port->membase)
> + return -ENODEV;
> +
> + if (options)
> + uart_parse_options(options, &baud, &parity, &bits, &flow);
> +
> + return uart_set_options(port, co, baud, parity, bits, flow);
> +}
> +
> +static struct console liteuart_console = {
> + .name = "liteuart",
> + .write = liteuart_console_write,
> + .device = uart_console_device,
> + .setup = liteuart_console_setup,
> + .flags = CON_PRINTBUFFER,
> + .index = -1,
> + .data = &liteuart_driver,
> +};
> +
> +static int __init liteuart_console_init(void)
> +{
> + register_console(&liteuart_console);
> +
> + return 0;
> +}
> +console_initcall(liteuart_console_init);
> +#endif /* CONFIG_SERIAL_LITEUART_CONSOLE */
> +
> +static int __init liteuart_init(void)
> +{
> + int res;
> +
> + res = uart_register_driver(&liteuart_driver);
> + if (res)
> + return res;
> +
> + res = platform_driver_register(&liteuart_platform_driver);
> + if (res) {
> + uart_unregister_driver(&liteuart_driver);
> + return res;
> + }
> +
> + return 0;
> +}
> +
> +static void __exit liteuart_exit(void)
> +{
> + platform_driver_unregister(&liteuart_platform_driver);
> + uart_unregister_driver(&liteuart_driver);
> +}
> +
> +module_init(liteuart_init);
> +module_exit(liteuart_exit);
> +
> +MODULE_AUTHOR("Antmicro <www.antmicro.com>");
> +MODULE_DESCRIPTION("LiteUART serial driver");
> +MODULE_LICENSE("GPL v2");
> +MODULE_ALIAS("platform: liteuart");
> --
> 2.20.1
>

--
Mateusz Holenko
Antmicro Ltd | www.antmicro.com
Roosevelta 22, 60-829 Poznan, Poland