Subject: [PATCH] atmel_serial: Atmel RS485 support

From: [email-masked] (Ryan Mallon)
Date: Mon, 22 Mar 2010 09:15:31 +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,
>
>           Claudio
>
Please post patches inline in the message body as it makes them easier
to reply to. Some comments below:

> 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 */ 
Same here.

> + /* 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 as the beginning
of each line in a multi-line 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)
	goto -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) { + rs485conf.flags &= ~(SER_RS485_ENABLED); 
Again, I would revert the logic of this if statement.

> + } 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, can you please
reformat, ie:

UART_PUT_IDR(port, ATMEL_US_ENDRX | ATMEL_US_TIMEOUT | 
	     port->read_status_mask);

> } else UART_PUT_IDR(port, ATMEL_US_RXRDY); 

Please use braces even on single line else statements in the case where the
if statement 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; 
Moving this declaration to the top of the function will remove two 
indentation levels.

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 
~Ryan