Subject: [PATCH] atmel_serial: Atmel RS485 support

From: [email-masked] (Ryan Mallon)
Date: Mon, 22 Mar 2010 10:55:48 +1300

Claudio Scordino wrote:
> Hi all,
>
>   this is a patch to add RS485 support to the atmel_serial driver.
>
> The patch has been successfully tested by Sebastian Heutling (CC:-ed).
>
> Feedback (comments, suggestions, further testing) is welcome.
>
> Many thanks,
>
Ugh, not sure what happened to my previous email. It looked fine in
Thunderbird before I sent it. Hopefully this works a bit better:

> atmel_serial: RS485 support
>
> Signed-off-by: Claudio Scordino <[email-masked]>
> Signed-off-by: Michael Trimarchi <[email-masked]>
> Signed-off-by: Rick Bronson <[email-masked]>
> Signed-off-by: Sebastian Heutling <[email-masked]>
> ---
>  arch/arm/include/asm/ioctls.h           |    2 +
>  arch/arm/mach-at91/include/mach/board.h |    4 +
>  drivers/serial/atmel_serial.c           |  247
> ++++++++++++++++++++++++++-----
>  3 files changed, 218 insertions(+), 35 deletions(-)
>
> diff --git a/arch/arm/include/asm/ioctls.h b/arch/arm/include/asm/ioctls.h
> index a91d8a1..82f2177 100644
> --- a/arch/arm/include/asm/ioctls.h
> +++ b/arch/arm/include/asm/ioctls.h
> @@ -70,6 +70,8 @@
>  #define TIOCGICOUNT    0x545D    /* read serial port inline interrupt
> counts */
>  #define FIOQSIZE    0x545E
>  
> +#define TIOCSRS485    0x5461
> +
>  /* Used for packet mode */
>  #define TIOCPKT_DATA         0
>  #define TIOCPKT_FLUSHREAD     1
> diff --git a/arch/arm/mach-at91/include/mach/board.h
> b/arch/arm/mach-at91/include/mach/board.h
> index ceaec6c..21f1308 100644
> --- a/arch/arm/mach-at91/include/mach/board.h
> +++ b/arch/arm/mach-at91/include/mach/board.h
> @@ -39,6 +39,7 @@
>  #include <linux/usb/atmel_usba_udc.h>
>  #include <linux/atmel-mci.h>
>  #include <sound/atmel-ac97c.h>
> +#include <linux/serial.h>
>  
>   /* USB Device */
>  struct at91_udc_data {
> @@ -146,6 +147,9 @@ struct atmel_uart_data {
>      short        use_dma_tx;    /* use transmit DMA? */
>      short        use_dma_rx;    /* use receive DMA? */
>      void __iomem    *regs;        /* virtual base address, if any */
> +    struct serial_rs485    rs485;        /* this flag specifies
> +                           if the uart must be used
> +                           as RS485 */
>  };

This comment is misleading, it is a struct not a flag. The comment should
say that it is the rs485 settings for the uart.

>  extern void __init at91_add_device_serial(void);
>  
> diff --git a/drivers/serial/atmel_serial.c b/drivers/serial/atmel_serial.c
> index 2c9bf9b..21bf3a8 100644
> --- a/drivers/serial/atmel_serial.c
> +++ b/drivers/serial/atmel_serial.c
> @@ -38,6 +38,7 @@
>  #include <linux/dma-mapping.h>
>  #include <linux/atmel_pdc.h>
>  #include <linux/atmel_serial.h>
> +#include <linux/uaccess.h>
>  
>  #include <asm/io.h>
>  
> @@ -59,6 +60,9 @@
>  
>  #include <linux/serial_core.h>
>  
> +static void atmel_start_rx(struct uart_port *port);
> +static void atmel_stop_rx(struct uart_port *port);

Can you move these functions, so that these declarations are not needed?

>  #ifdef CONFIG_SERIAL_ATMEL_TTYAT
>  
>  /* Use device name ttyAT, major 204 and minor 154-169.  This is
> necessary if we
> @@ -93,6 +97,7 @@
>  #define UART_GET_BRGR(port)    __raw_readl((port)->membase +
> ATMEL_US_BRGR)
>  #define UART_PUT_BRGR(port,v)    __raw_writel(v, (port)->membase +
> ATMEL_US_BRGR)
>  #define UART_PUT_RTOR(port,v)    __raw_writel(v, (port)->membase +
> ATMEL_US_RTOR)
> +#define UART_PUT_TTGR(port, v)    __raw_writel(v, (port)->membase +
> ATMEL_US_TTGR)
>  
>   /* PDC registers */
>  #define UART_PUT_PTCR(port,v)    __raw_writel(v, (port)->membase +
> ATMEL_PDC_PTCR)
> @@ -147,6 +152,16 @@ struct atmel_uart_port {
>      unsigned int        irq_status_prev;
>  
>      struct circ_buf        rx_ring;
> +
> +    struct serial_rs485    rs485;        /* this flag specifies
> +                           if the uart must be used
> +                           as RS485 */
> +    /* Fields related to interrupts:
> +       if (rs485)        = ATMEL_US_TXEMPTY
> +       else if (use_dma_tx)    = ATMEL_US_ENDTX | ATMEL_US_TXBUFE
> +       else            = ATMEL_US_TXRDY;
> +     */

This comment doesn't really belong here. Also, please use *s at the
beginning of each line in a multiline comment.

> +    unsigned int        tx_done_mask;
>  };
>  
>  static struct atmel_uart_port atmel_ports[ATMEL_MAX_UART];
> @@ -187,6 +202,85 @@ static bool atmel_use_dma_tx(struct uart_port *port)
>  }
>  #endif
>  
> +/* Enable or disable the rs485 support */
> +void atmel_enable_disable_rs485(struct uart_port *port, struct
> serial_rs485 *rs485conf)
> +{
Please change the name of this function. Something like
atmel_config_rs485 would be better.

> +    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
> +    unsigned long flags;
> +    unsigned int mode;
> +
> +    spin_lock_irqsave(&port->lock, flags);
> +
> +    mode = UART_GET_MR(port);
> +
> +    /* Resetting serial mode to RS232 (0x0) */
> +    mode &= ~ATMEL_US_USMODE;
> +
> +    atmel_port->rs485 = *rs485conf;
> +
> +    if (!(rs485conf->flags & SER_RS485_ENABLED)) {
Reversing the logic of this if statement will make it slightly easier to
read.

> +        dev_dbg(port->dev, "Setting UART to RS232\n");
> +        if (atmel_use_dma_tx(port))
> +            atmel_port->tx_done_mask = ATMEL_US_ENDTX | ATMEL_US_TXBUFE;
> +        else
> +            atmel_port->tx_done_mask = ATMEL_US_TXRDY;
> +    } else {
> +        dev_dbg(port->dev, "Setting UART to RS485\n");
> +        atmel_port->tx_done_mask = ATMEL_US_TXEMPTY;
> +        UART_PUT_TTGR(port, rs485conf->delay_rts_before_send);
> +        mode |= ATMEL_US_USMODE_RS485;
> +    }
> +    UART_PUT_MR(port, mode);
> +
> +    spin_unlock_irqrestore(&port->lock, flags);
> +}
> +
> +
> +static ssize_t show_rs485(struct device *dev, struct device_attribute
> *attr, \
> +               char *buf)
> +{
> +    struct platform_device *pdev = to_platform_device(dev);
> +    struct uart_port *port = platform_get_drvdata(pdev);
> +    unsigned int current_mode;
> +
> +    current_mode = UART_GET_MR(port);
> +    current_mode &= ATMEL_US_USMODE;

current_mode = UART_GET_MR(port) & ATMEL_US_USMODE;

> +    return snprintf(buf, PAGE_SIZE, "%u\n", current_mode);
> +}
> +
> +static ssize_t set_rs485(struct device *dev, struct device_attribute
> *attr, \
> +              const char *buf, size_t len)
> +{
> +    struct platform_device *pdev = to_platform_device(dev);
> +    struct uart_port *port = platform_get_drvdata(pdev);
> +    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
> +    struct serial_rs485 rs485conf = atmel_port->rs485;
> +    unsigned int value;
> +
> +    if (buf == NULL)
> +        goto err;
if (!buf)
    return -EINVAL;
> +
> +    value = simple_strtoul(buf, NULL, 10);
> +
> +    if ((value != 0) && (value != 1))
> +        goto err;

Is there any reason to be so strict on the values, you could just do this:

value = !!(simple_strtoul(buf, NULL, 0));

which will allow the user to use values in any base, and will convert any
non-zero values to 1.
> +
> +    if (!value) {
Again, I would revert the logic of this if statement.

> +        rs485conf.flags &= ~(SER_RS485_ENABLED);
> +    } else {
> +        rs485conf.flags |= SER_RS485_ENABLED;
> +        /* 0x4 is the normal reset value. */
> +        rs485conf.delay_rts_before_send = 0x00000004;
> +    }
> +
> +    atmel_enable_disable_rs485(port, &rs485conf);
> +
> +err:
> +    return strnlen(buf, PAGE_SIZE);
> +}
> +
> +static DEVICE_ATTR(rs485, 0644, show_rs485, set_rs485);
> +
>  /*
>   * Return TIOCSER_TEMT when transmitter FIFO and Shift register is empty.
>   */
> @@ -202,6 +296,7 @@ static void atmel_set_mctrl(struct uart_port
> *port, u_int mctrl)
>  {
>      unsigned int control = 0;
>      unsigned int mode;
> +    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
>  
>  #ifdef CONFIG_ARCH_AT91RM9200
>      if (cpu_is_at91rm9200()) {
> @@ -236,6 +331,16 @@ static void atmel_set_mctrl(struct uart_port
> *port, u_int mctrl)
>          mode |= ATMEL_US_CHMODE_LOC_LOOP;
>      else
>          mode |= ATMEL_US_CHMODE_NORMAL;
> +
> +    /* Resetting serial mode to RS232 (0x0) */
> +    mode &= ~ATMEL_US_USMODE;
> +
> +    if (atmel_port->rs485.flags & SER_RS485_ENABLED) {
> +        dev_dbg(port->dev, "Keeping UART to RS485\n");
> +        UART_PUT_TTGR(port, atmel_port->rs485.delay_rts_before_send);
> +        mode |= ATMEL_US_USMODE_RS485;
> +    } else
> +        dev_dbg(port->dev, "Keeping UART to RS232\n");
>      UART_PUT_MR(port, mode);
>  }
>  
> @@ -268,12 +373,17 @@ static u_int atmel_get_mctrl(struct uart_port *port)
>   */
>  static void atmel_stop_tx(struct uart_port *port)
>  {
> +    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
> +
>      if (atmel_use_dma_tx(port)) {
>          /* disable PDC transmit */
>          UART_PUT_PTCR(port, ATMEL_PDC_TXTDIS);
> -        UART_PUT_IDR(port, ATMEL_US_ENDTX | ATMEL_US_TXBUFE);
> -    } else
> -        UART_PUT_IDR(port, ATMEL_US_TXRDY);
> +    }
> +    /* Disable interrupts */
> +    UART_PUT_IDR(port, atmel_port->tx_done_mask);
> +
> +    if (atmel_port->rs485.flags & SER_RS485_ENABLED)
> +        atmel_start_rx(port);
>  }
>  
>  /*
> @@ -281,17 +391,22 @@ static void atmel_stop_tx(struct uart_port *port)
>   */
>  static void atmel_start_tx(struct uart_port *port)
>  {
> +    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
> +
>      if (atmel_use_dma_tx(port)) {
>          if (UART_GET_PTSR(port) & ATMEL_PDC_TXTEN)
>              /* The transmitter is already running.  Yes, we
>                 really need this.*/
>              return;
>  
> -        UART_PUT_IER(port, ATMEL_US_ENDTX | ATMEL_US_TXBUFE);
> +        if (atmel_port->rs485.flags & SER_RS485_ENABLED)
> +            atmel_stop_rx(port);
> +
>          /* re-enable PDC transmit */
>          UART_PUT_PTCR(port, ATMEL_PDC_TXTEN);
> -    } else
> -        UART_PUT_IER(port, ATMEL_US_TXRDY);
> +    }
> +    /* Enable interrupts */
> +    UART_PUT_IER(port, atmel_port->tx_done_mask);
>  }
>  
>  /*
> @@ -302,12 +417,28 @@ static void atmel_stop_rx(struct uart_port *port)
>      if (atmel_use_dma_rx(port)) {
>          /* disable PDC receive */
>          UART_PUT_PTCR(port, ATMEL_PDC_RXTDIS);
> -        UART_PUT_IDR(port, ATMEL_US_ENDRX | ATMEL_US_TIMEOUT);
> +        UART_PUT_IDR(port, ATMEL_US_ENDRX | ATMEL_US_TIMEOUT |
> port->read_status_mask);

This line, and a couple of others, extend over 80 characters. Could you
please split them up.

>      } else
>          UART_PUT_IDR(port, ATMEL_US_RXRDY);

Please use braces for single line else statements when the if clause has
braces.

>  }
>  
>  /*
> + * start receiving - port is in process of being opened.
> + */
> +static void atmel_start_rx(struct uart_port *port)
> +{
> +    UART_PUT_CR(port, ATMEL_US_RSTSTA);  /* reset status and receiver */
> +
> +    if (atmel_use_dma_rx(port)) {
> +        /* enable PDC controller */
> +        UART_PUT_IER(port, ATMEL_US_ENDRX | ATMEL_US_TIMEOUT |
> port->read_status_mask);
> +        UART_PUT_PTCR(port, ATMEL_PDC_RXTEN);
> +    } else
> +        UART_PUT_IER(port, ATMEL_US_RXRDY);
> +}
> +
> +
> +/*
>   * Enable modem status interrupts
>   */
>  static void atmel_enable_ms(struct uart_port *port)
> @@ -428,8 +559,9 @@ static void atmel_rx_chars(struct uart_port *port)
>  static void atmel_tx_chars(struct uart_port *port)
>  {
>      struct circ_buf *xmit = &port->state->xmit;
> +    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
>  
> -    if (port->x_char && UART_GET_CSR(port) & ATMEL_US_TXRDY) {
> +    if (port->x_char && UART_GET_CSR(port) & atmel_port->tx_done_mask) {
>          UART_PUT_CHAR(port, port->x_char);
>          port->icount.tx++;
>          port->x_char = 0;
> @@ -437,7 +569,7 @@ static void atmel_tx_chars(struct uart_port *port)
>      if (uart_circ_empty(xmit) || uart_tx_stopped(port))
>          return;
>  
> -    while (UART_GET_CSR(port) & ATMEL_US_TXRDY) {
> +    while (UART_GET_CSR(port) & atmel_port->tx_done_mask) {
>          UART_PUT_CHAR(port, xmit->buf[xmit->tail]);
>          xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
>          port->icount.tx++;
> @@ -449,7 +581,8 @@ static void atmel_tx_chars(struct uart_port *port)
>          uart_write_wakeup(port);
>  
>      if (!uart_circ_empty(xmit))
> -        UART_PUT_IER(port, ATMEL_US_TXRDY);
> +        /* Enable interrupts */
> +        UART_PUT_IER(port, atmel_port->tx_done_mask);
>  }
>  
>  /*
> @@ -501,18 +634,10 @@ atmel_handle_transmit(struct uart_port *port,
> unsigned int pending)
>  {
>      struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
>  
> -    if (atmel_use_dma_tx(port)) {
> -        /* PDC transmit */
> -        if (pending & (ATMEL_US_ENDTX | ATMEL_US_TXBUFE)) {
> -            UART_PUT_IDR(port, ATMEL_US_ENDTX | ATMEL_US_TXBUFE);
> -            tasklet_schedule(&atmel_port->tasklet);
> -        }
> -    } else {
> -        /* Interrupt transmit */
> -        if (pending & ATMEL_US_TXRDY) {
> -            UART_PUT_IDR(port, ATMEL_US_TXRDY);
> -            tasklet_schedule(&atmel_port->tasklet);
> -        }
> +    if (pending & atmel_port->tx_done_mask) {
> +        /* Either PDC or interrupt transmission */
> +        UART_PUT_IDR(port, atmel_port->tx_done_mask);
> +        tasklet_schedule(&atmel_port->tasklet);
>      }
>  }
>  
> @@ -590,9 +715,15 @@ static void atmel_tx_dma(struct uart_port *port)
>  
>          UART_PUT_TPR(port, pdc->dma_addr + xmit->tail);
>          UART_PUT_TCR(port, count);
> -        /* re-enable PDC transmit and interrupts */
> +        /* re-enable PDC transmit */
>          UART_PUT_PTCR(port, ATMEL_PDC_TXTEN);
> -        UART_PUT_IER(port, ATMEL_US_ENDTX | ATMEL_US_TXBUFE);
> +        /* Enable interrupts */
> +        UART_PUT_IER(port, atmel_port->tx_done_mask);
> +    } else {
> +        if (atmel_port->rs485.flags & SER_RS485_ENABLED) {
> +            /* DMA done, stop TX, start RX for RS485 */
> +            atmel_start_rx(port);
> +        }
>      }
>  
>      if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
> @@ -1017,6 +1148,7 @@ static void atmel_set_termios(struct uart_port
> *port, struct ktermios *termios,
>  {
>      unsigned long flags;
>      unsigned int mode, imr, quot, baud;
> +    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
>  
>      /* Get current mode register */
>      mode = UART_GET_MR(port) & ~(ATMEL_US_USCLKS | ATMEL_US_CHRL
> @@ -1115,6 +1247,16 @@ static void atmel_set_termios(struct uart_port
> *port, struct ktermios *termios,
>      /* disable receiver and transmitter */
>      UART_PUT_CR(port, ATMEL_US_TXDIS | ATMEL_US_RXDIS);
>  
> +    /* Resetting serial mode to RS232 (0x0) */
> +    mode &= ~ATMEL_US_USMODE;
> +
> +    if (atmel_port->rs485.flags & SER_RS485_ENABLED) {
> +        dev_dbg(port->dev, "Keeping UART to RS485\n");
> +        UART_PUT_TTGR(port, atmel_port->rs485.delay_rts_before_send);
> +        mode |= ATMEL_US_USMODE_RS485;
> +    } else
> +        dev_dbg(port->dev, "Keeping UART to RS232\n");
> +
>      /* set the parity, stop bits and data size */
>      UART_PUT_MR(port, mode);
>  
> @@ -1231,6 +1373,31 @@ static void atmel_poll_put_char(struct
> uart_port *port, unsigned char ch)
>  }
>  #endif
>  
> +static int atmel_ioctl(struct uart_port *port, unsigned int cmd,
> unsigned long arg)
> +{
> +
> +    switch (cmd) {
> +    case TIOCSRS485:
> +        {
> +            struct serial_rs485 rs485conf;

If you move this declaration to the top of the function you will save
two levels of indentation.

Is it necessary to have both an ioctl and a sysfs control for putting
the uart into rs485 mode? The ioctl is more standardised, so perhaps
drop the sysfs control?

> +            if (copy_from_user(&rs485conf, (struct serial_rs485 *) arg,
> +                        sizeof(rs485conf)))
> +                return -EFAULT;
> +
> +            dev_dbg(port->dev, "enable e/o disable rs485\n");
> +
> +            atmel_enable_disable_rs485(port, &rs485conf);
> +        }
> +        break;
> +
> +    default:
> +        return -ENOIOCTLCMD;
> +    }
> +    return 0;
> +}
> +
> +
> +
>  static struct uart_ops atmel_pops = {
>      .tx_empty    = atmel_tx_empty,
>      .set_mctrl    = atmel_set_mctrl,
> @@ -1250,6 +1417,7 @@ static struct uart_ops atmel_pops = {
>      .config_port    = atmel_config_port,
>      .verify_port    = atmel_verify_port,
>      .pm        = atmel_serial_pm,
> +    .ioctl        = atmel_ioctl,
>  #ifdef CONFIG_CONSOLE_POLL
>      .poll_get_char    = atmel_poll_get_char,
>      .poll_put_char    = atmel_poll_put_char,
> @@ -1265,13 +1433,12 @@ static void __devinit atmel_init_port(struct
> atmel_uart_port *atmel_port,
>      struct uart_port *port = &atmel_port->uart;
>      struct atmel_uart_data *data = pdev->dev.platform_data;
>  
> -    port->iotype    = UPIO_MEM;
> -    port->flags    = UPF_BOOT_AUTOCONF;
> -    port->ops    = &atmel_pops;
> -    port->fifosize    = 1;
> -    port->line    = pdev->id;
> -    port->dev    = &pdev->dev;
> -
> +    port->iotype        = UPIO_MEM;
> +    port->flags        = UPF_BOOT_AUTOCONF;
> +    port->ops        = &atmel_pops;
> +    port->fifosize        = 1;
> +    port->line        = pdev->id;
> +    port->dev        = &pdev->dev;
>      port->mapbase    = pdev->resource[0].start;
>      port->irq    = pdev->resource[1].start;
>  
> @@ -1299,8 +1466,15 @@ static void __devinit atmel_init_port(struct
> atmel_uart_port *atmel_port,
>  
>      atmel_port->use_dma_rx = data->use_dma_rx;
>      atmel_port->use_dma_tx = data->use_dma_tx;
> -    if (atmel_use_dma_tx(port))
> +    atmel_port->rs485    = data->rs485;
> +    /* Use TXEMPTY for interrupt when rs485 else TXRDY or ENDTX|TXBUFE */
> +    if (atmel_port->rs485.flags & SER_RS485_ENABLED)
> +        atmel_port->tx_done_mask = ATMEL_US_TXEMPTY;
> +    else if (atmel_use_dma_tx(port)) {
>          port->fifosize = PDC_BUFFER_SIZE;
> +        atmel_port->tx_done_mask = ATMEL_US_ENDTX | ATMEL_US_TXBUFE;
> +    } else
> +        atmel_port->tx_done_mask = ATMEL_US_TXRDY;
>  }
>  
>  /*
> @@ -1334,6 +1508,7 @@ static void atmel_console_putchar(struct
> uart_port *port, int ch)
>  static void atmel_console_write(struct console *co, const char *s,
> u_int count)
>  {
>      struct uart_port *port = &atmel_ports[co->index].uart;
> +    struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
>      unsigned int status, imr;
>      unsigned int pdc_tx;
>  
> @@ -1341,7 +1516,7 @@ static void atmel_console_write(struct console
> *co, const char *s, u_int count)
>       * First, save IMR and then disable interrupts
>       */
>      imr = UART_GET_IMR(port);
> -    UART_PUT_IDR(port, ATMEL_US_RXRDY | ATMEL_US_TXRDY);
> +    UART_PUT_IDR(port, ATMEL_US_RXRDY | atmel_port->tx_done_mask);
>  
>      /* Store PDC transmit status and disable it */
>      pdc_tx = UART_GET_PTSR(port) & ATMEL_PDC_TXTEN;
> @@ -1355,7 +1530,7 @@ static void atmel_console_write(struct console
> *co, const char *s, u_int count)
>       */
>      do {
>          status = UART_GET_CSR(port);
> -    } while (!(status & ATMEL_US_TXRDY));
> +    } while (!(status & atmel_port->tx_done_mask));
>  
>      /* Restore PDC transmit status */
>      if (pdc_tx)
> @@ -1587,7 +1762,7 @@ static int __devinit atmel_serial_probe(struct
> platform_device *pdev)
>      device_init_wakeup(&pdev->dev, 1);
>      platform_set_drvdata(pdev, port);
>  
> -    return 0;
> +    return device_create_file(&(pdev->dev), &dev_attr_rs485);
>  
>  err_add_port:
>      kfree(port->rx_ring.buf);
> @@ -1619,6 +1794,8 @@ static int __devexit atmel_serial_remove(struct
> platform_device *pdev)
>  
>      clk_put(atmel_port->clk);
>  
> +    device_remove_file(&(pdev->dev), &dev_attr_rs485);
> +
>      return ret;
>  }
>  
> -- 
> 1.6.0.4