Re: [PATCH v3 5/5] drivers/tty/serial: add LiteUART driver

[Mateusz Holenko <mholenko@antmicro.com>]

On Tue, Feb 25, 2020 at 9:47 AM 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 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       |  32 ++-
>  drivers/tty/serial/Makefile      |   1 +
>  drivers/tty/serial/liteuart.c    | 411 +++++++++++++++++++++++++++++++
>  include/uapi/linux/serial_core.h |   3 +
>  5 files changed, 447 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/tty/serial/liteuart.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 22a67514ace3..9b294f083640 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -9732,6 +9732,7 @@ S:        Maintained
>  F:     Documentation/devicetree/bindings/*/litex,*.yaml
>  F:     drivers/soc/litex/litex_soc_ctrl.c
>  F:     include/linux/litex.h
> +F:     drivers/tty/serial/liteuart.c
>
>  LIVE PATCHING
>  M:     Josh Poimboeuf <jpoimboe@redhat.com>
> diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
> index 52eaac21ff9f..577c088b9feb 100644
> --- a/drivers/tty/serial/Kconfig
> +++ b/drivers/tty/serial/Kconfig
> @@ -529,7 +529,7 @@ config SERIAL_IMX_CONSOLE
>
>  config SERIAL_UARTLITE
>         tristate "Xilinx uartlite serial port support"
> -       depends on HAS_IOMEM
> +       depends on HAS_IOMEM && LITEX_SOC_CONTROLLER

Just noticed this - it's wrong. We don't want to change Xilinx UARTLITE config.
It's SERIAL_LITEUART that should be dependent on LITEX_SOC_CONTROLLER.

>         select SERIAL_CORE
>         help
>           Say Y here if you want to use the Xilinx uartlite serial controller.
> @@ -1572,6 +1572,36 @@ 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

This should also depend 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..184ecb9f51f3
> --- /dev/null
> +++ b/drivers/tty/serial/liteuart.c
> @@ -0,0 +1,411 @@
> +// 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>
> +
> +/* module-related defines */
> +#define DRIVER_NAME    "liteuart"
> +#define DRIVER_MAJOR   0
> +#define DRIVER_MINOR   0
> +#define DEV_NAME       "ttyLXU"
> +
> +/*
> + * 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 SIZE_RXTX      1
> +#define OFF_TXFULL     0x04
> +#define SIZE_TXFULL    1
> +#define OFF_RXEMPTY    0x08
> +#define SIZE_RXEMPTY   1
> +#define OFF_EV_STATUS  0x0c
> +#define SIZE_EV_STATUS 1
> +#define OFF_EV_PENDING 0x10
> +#define SIZE_EV_PENDING        1
> +#define OFF_EV_ENABLE  0x14
> +#define SIZE_EV_ENABLE 1
> +
> +/* 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 struct liteuart_port liteuart_ports[CONFIG_SERIAL_LITEUART_MAX_PORTS];
> +static DECLARE_BITMAP(liteuart_ports_in_use, CONFIG_SERIAL_LITEUART_MAX_PORTS);
> +
> +#ifdef CONFIG_SERIAL_LITEUART_CONSOLE
> +static struct console liteuart_console;
> +#endif
> +
> +static struct uart_driver liteuart_driver = {
> +       .owner = THIS_MODULE,
> +       .driver_name = DRIVER_NAME,
> +       .dev_name = DEV_NAME,
> +       .major = DRIVER_MAJOR,
> +       .minor = DRIVER_MINOR,
> +       .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,
> +                       SIZE_RXEMPTY)) == 1) {
> +               ch = litex_get_reg(membase + OFF_RXTX, SIZE_RXTX);
> +               port->icount.rx++;
> +
> +               /* necessary for RXEMPTY to refresh its value */
> +               litex_set_reg(membase + OFF_EV_PENDING,
> +                       SIZE_EV_PENDING, 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, SIZE_TXFULL))
> +               cpu_relax();
> +
> +       litex_set_reg(port->membase + OFF_RXTX, SIZE_RXTX, 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, SIZE_TXFULL))
> +               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,
> +                       SIZE_RXTX, 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, SIZE_EV_ENABLE, 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 (port->type == PORT_LITEUART) ? DRIVER_NAME : NULL;
> +}
> +
> +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)
> +{
> +       if (flags & UART_CONFIG_TYPE)
> +               port->type = PORT_LITEUART;
> +}
> +
> +static int liteuart_verify_port(struct uart_port *port,
> +                               struct serial_struct *ser)
> +{
> +       if (port->type != PORT_UNKNOWN && ser->type != PORT_LITEUART)
> +               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;
> +       int dev_id;
> +
> +       if (!litex_check_accessors())
> +               return -EPROBE_DEFER;
> +
> +       /* no device tree */
> +       if (!np)
> +               return -ENODEV;
> +
> +       /* look for aliases; auto-enumerate for free index if not found */
> +       dev_id = of_alias_get_id(np, "serial");
> +       if (dev_id < 0)
> +               dev_id = find_first_zero_bit(liteuart_ports_in_use,
> +                                            CONFIG_SERIAL_LITEUART_MAX_PORTS);
> +
> +       if (dev_id >= CONFIG_SERIAL_LITEUART_MAX_PORTS)
> +               return -ENODEV;
> +
> +       if (test_and_set_bit(dev_id, liteuart_ports_in_use))
> +               return -EBUSY;
> +
> +       uart = &liteuart_ports[dev_id];
> +       port = &uart->port;
> +
> +       /* get {map,mem}base */
> +       port->mapbase = platform_get_resource(pdev, IORESOURCE_MEM, 0)->start;
> +       port->membase = of_iomap(np, 0);
> +       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;
> +
> +       return uart_add_one_port(&liteuart_driver,
> +                                &liteuart_ports[dev_id].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 = DRIVER_NAME,
> +               .of_match_table = of_match_ptr(liteuart_of_match),
> +       },
> +};
> +
> +#ifdef CONFIG_SERIAL_LITEUART_CONSOLE
> +
> +static void liteuart_console_write(struct console *co, const char *s,
> +       unsigned int count)
> +{
> +       struct uart_port *port = &liteuart_ports[co->index].port;
> +       unsigned long flags;
> +
> +       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 uart_port *port;
> +       int baud = 115200;
> +       int bits = 8;
> +       int parity = 'n';
> +       int flow = 'n';
> +
> +       port = &liteuart_ports[co->index].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 = DRIVER_NAME,
> +       .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:" DRIVER_NAME);
> diff --git a/include/uapi/linux/serial_core.h b/include/uapi/linux/serial_core.h
> index 8ec3dd742ea4..449b8fe9273c 100644
> --- a/include/uapi/linux/serial_core.h
> +++ b/include/uapi/linux/serial_core.h
> @@ -293,4 +293,7 @@
>  /* Freescale LINFlexD UART */
>  #define PORT_LINFLEXUART       122
>
> +/* LiteUART */
> +#define PORT_LITEUART  123
> +
>  #endif /* _UAPILINUX_SERIAL_CORE_H */
> --
> 2.25.0
>


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