ARM: 6092/1: atmel_serial: support for RS485 communications

Final version of the patch that adds support for RS485 communications to the atmel_serial driver.

The patch has been already sent and discussed on both linux-kernel and linux-arm-kernel mailing lists several times.

Many people collaborated to improve and test the code:

Tested-by: Sebastian Heutling <Sebastian.Heutling@who-ing.de>
Tested-by: Bernhard Roth <br@pwrnet.de>
Reviewed-by: Ryan Mallon <ryan@bluewatersys.com>
Signed-off-by: Claudio Scordino <claudio@evidence.eu.com>
Signed-off-by: Michael Trimarchi <michael@evidence.eu.com>
Signed-off-by: Rick Bronson <rick@efn.org>
Signed-off-by: Sebastian Heutling <Sebastian.Heutling@who-ing.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 173 insertions, 34 deletions

diff --git a/drivers/serial/atmel_serial.c b/drivers/serial/atmel_serial.c
index 2c9bf9b68327..eed3c2d8dd1c 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);
+
 #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 +152,9 @@ struct atmel_uart_port {
         unsigned int            irq_status_prev;
 
         struct circ_buf         rx_ring;
+
+        struct serial_rs485     rs485;          /* rs485 settings */
+        unsigned int            tx_done_mask;
 };
 
 static struct atmel_uart_port atmel_ports[ATMEL_MAX_UART];
@@ -187,6 +195,46 @@ static bool atmel_use_dma_tx(struct uart_port *port)
 }
 #endif
 
+/* Enable or disable the rs485 support */
+void atmel_config_rs485(struct uart_port *port, struct serial_rs485 *rs485conf)
+{
+        struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
+        unsigned int mode;
+
+        spin_lock(&port->lock);
+
+        /* Disable interrupts */
+        UART_PUT_IDR(port, atmel_port->tx_done_mask);
+
+        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) {
+                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;
+        } else {
+                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;
+        }
+        UART_PUT_MR(port, mode);
+
+        /* Enable interrupts */
+        UART_PUT_IER(port, atmel_port->tx_done_mask);
+
+        spin_unlock(&port->lock);
+
+}
+
 /*
  * Return TIOCSER_TEMT when transmitter FIFO and Shift register is empty.
  */
@@ -202,6 +250,7 @@ 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 +285,17 @@ 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, "Setting 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, "Setting UART to RS232\n");
+        }
         UART_PUT_MR(port, mode);
 }
 
@@ -268,12 +328,17 @@ 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 +346,39 @@ 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);
+}
+
+/*
+ * 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);
+        }
 }
 
 /*
@@ -302,9 +389,11 @@ 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);
-        } else
+                UART_PUT_IDR(port, ATMEL_US_ENDRX | ATMEL_US_TIMEOUT |
+                        port->read_status_mask);
+        } else {
                 UART_PUT_IDR(port, ATMEL_US_RXRDY);
+        }
 }
 
 /*
@@ -428,8 +517,9 @@ 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 +527,7 @@ 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 +539,8 @@ 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 +592,10 @@ 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 +673,15 @@ 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 +1106,7 @@ 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 +1205,17 @@ 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, "Setting 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, "Setting UART to RS232\n");
+        }
+
         /* set the parity, stop bits and data size */
         UART_PUT_MR(port, mode);
 
@@ -1231,6 +1332,35 @@ 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)
+{
+        struct serial_rs485 rs485conf;
+
+        switch (cmd) {
+        case TIOCSRS485:
+                if (copy_from_user(&rs485conf, (struct serial_rs485 *) arg,
+                                        sizeof(rs485conf)))
+                        return -EFAULT;
+
+                atmel_config_rs485(port, &rs485conf);
+                break;
+
+        case TIOCGRS485:
+                if (copy_to_user((struct serial_rs485 *) arg,
+                                        &(to_atmel_uart_port(port)->rs485),
+                                        sizeof(rs485conf)))
+                        return -EFAULT;
+                break;
+
+        default:
+                return -ENOIOCTLCMD;
+        }
+        return 0;
+}
+
+
+
 static struct uart_ops atmel_pops = {
         .tx_empty       = atmel_tx_empty,
         .set_mctrl      = atmel_set_mctrl,
@@ -1250,6 +1380,7 @@ 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 +1396,12 @@ 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 +1429,16 @@ 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 +1472,7 @@ 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 +1480,7 @@ 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;