[PATCH -mm v4 0/9] atmel_serial cleanups and improvements

[PATCH -mm v4 0/9] atmel_serial cleanups and improvements

[Haavard Skinnemoen]

The following patchset cleans up the atmel_serial driver a bit,
moves a significant portion of the interrupt handler into a tasklet,
and adds DMA support. This is the result of a combined effort by Chip
Coldwell, Remy Bohmer and me. The patches should apply cleanly onto
Linus' latest git tree, and I've also tested it on -mm (with a couple
of avr32 fixes applied to make the rest of the tree compile.)

With DMA, I see transfer rates around 92 kbps when transferring a big
file using ZModem (both directions are roughly the same.) I've also
tested the same thing with a bunch of debug options enabled. The
transfer rate is slightly lower, but no errors are reported.

Note that break and error handling doesn't work too well with DMA
enabled. This is a common problem with all the efforts I've seen
adding DMA support to this driver (including my own). The PDC error
handling also accesses icount without locking. I'm tempted to just
ignore the problem for now and hopefully come up with a solution
later.

I think this stuff is ready for -mm now, but I'd like to see a couple
more ACKs from Andrew Victor and other people who may be familiar with
this driver and/or the serial/tty layer in general.

Changes since v3:
  * Added myself to MAINTAINERS
  * Additional cleanups suggested by Andrew Victor
  * Made PDC support configurable through Kconfig
  * Converted lots of potentially unsafe casts to use container_of()
  * Show tty name (not just "atmel_serial") in /proc/interrupts

Chip Coldwell (1):
      atmel_serial: Add DMA support

Haavard Skinnemoen (6):
      MAINTAINERS: Add myself as maintainer of the atmel_serial driver
      atmel_serial: Use cpu_relax() when busy-waiting
      atmel_serial: Use existing console options only if BRG is running
      atmel_serial: Fix bugs in probe() error path and remove()
      atmel_serial: Use container_of instead of direct cast
      atmel_serial: Show tty name in /proc/interrupts

Remy Bohmer (2):
      atmel_serial: Clean up the code
      atmel_serial: Split the interrupt handler

 MAINTAINERS                   |    6 +
 drivers/serial/Kconfig        |   15 +
 drivers/serial/atmel_serial.c |  888 +++++++++++++++++++++++++++++++++--------
 3 files changed, 740 insertions(+), 169 deletions(-)

[PATCH -mm v4 1/9] MAINTAINERS: Add myself as maintainer of the atmel_serial driver

[Haavard Skinnemoen]

The atmel_serial driver never had a MAINTAINERS entry, although Andrew
Victor has effectively been acting as a maintainer since he got the
driver merged into mainline in the first place.

I'll keep Cc'ing Andrew on all patches, but I'm going to take the
main responsibility for getting things moving upstream from now on.

Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Acked-by: Andrew Victor <linux@maxim.org.za>
---
 MAINTAINERS |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/MAINTAINERS b/MAINTAINERS
index 2340cfb..e349a9e 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -671,6 +671,12 @@ W:	http://www.atmel.com/products/AT91/
 W:	http://www.at91.com/
 S:	Maintained
 
+ATMEL AT91 / AT32 SERIAL DRIVER
+P:	Haavard Skinnemoen
+M:	hskinnemoen@atmel.com
+L:	linux-kernel@vger.kernel.org
+S:	Supported
+
 ATMEL LCDFB DRIVER
 P:	Nicolas Ferre
 M:	nicolas.ferre@atmel.com
-- 
1.5.3.8

[PATCH -mm v4 2/9] atmel_serial: Clean up the code

[Haavard Skinnemoen]

From: Remy Bohmer <linux@bohmer.net>

This patch cleans up the atmel_serial driver to conform the coding rules.
It contains no functional change.

Signed-off-by: Remy Bohmer <linux@bohmer.net>
Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
---
 drivers/serial/atmel_serial.c |  255 ++++++++++++++++++++++++-----------------
 1 files changed, 150 insertions(+), 105 deletions(-)

diff --git a/drivers/serial/atmel_serial.c b/drivers/serial/atmel_serial.c
index 111da57..ee5d844 100644
--- a/drivers/serial/atmel_serial.c
+++ b/drivers/serial/atmel_serial.c
@@ -74,6 +74,7 @@
 
 #define ATMEL_ISR_PASS_LIMIT	256
 
+/* UART registers. CR is write-only, hence no GET macro */
 #define UART_PUT_CR(port,v)	__raw_writel(v, (port)->membase + ATMEL_US_CR)
 #define UART_GET_MR(port)	__raw_readl((port)->membase + ATMEL_US_MR)
 #define UART_PUT_MR(port,v)	__raw_writel(v, (port)->membase + ATMEL_US_MR)
@@ -87,8 +88,6 @@
 #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_GET_CR(port)	__raw_readl((port)->membase + ATMEL_US_CR)		// is write-only
-
  /* PDC registers */
 #define UART_PUT_PTCR(port,v)	__raw_writel(v, (port)->membase + ATMEL_PDC_PTCR)
 #define UART_GET_PTSR(port)	__raw_readl((port)->membase + ATMEL_PDC_PTSR)
@@ -101,8 +100,6 @@
 
 #define UART_PUT_TPR(port,v)	__raw_writel(v, (port)->membase + ATMEL_PDC_TPR)
 #define UART_PUT_TCR(port,v)	__raw_writel(v, (port)->membase + ATMEL_PDC_TCR)
-//#define UART_PUT_TNPR(port,v)	__raw_writel(v, (port)->membase + ATMEL_PDC_TNPR)
-//#define UART_PUT_TNCR(port,v)	__raw_writel(v, (port)->membase + ATMEL_PDC_TNCR)
 
 static int (*atmel_open_hook)(struct uart_port *);
 static void (*atmel_close_hook)(struct uart_port *);
@@ -142,8 +139,8 @@ static void atmel_set_mctrl(struct uart_port *port, u_int mctrl)
 #ifdef CONFIG_ARCH_AT91RM9200
 	if (cpu_is_at91rm9200()) {
 		/*
-		 * AT91RM9200 Errata #39: RTS0 is not internally connected to PA21.
-		 *  We need to drive the pin manually.
+		 * AT91RM9200 Errata #39: RTS0 is not internally connected
+		 * to PA21. We need to drive the pin manually.
 		 */
 		if (port->mapbase == AT91RM9200_BASE_US0) {
 			if (mctrl & TIOCM_RTS)
@@ -228,7 +225,8 @@ static void atmel_stop_rx(struct uart_port *port)
  */
 static void atmel_enable_ms(struct uart_port *port)
 {
-	UART_PUT_IER(port, ATMEL_US_RIIC | ATMEL_US_DSRIC | ATMEL_US_DCDIC | ATMEL_US_CTSIC);
+	UART_PUT_IER(port, ATMEL_US_RIIC | ATMEL_US_DSRIC
+			| ATMEL_US_DCDIC | ATMEL_US_CTSIC);
 }
 
 /*
@@ -247,7 +245,7 @@ static void atmel_break_ctl(struct uart_port *port, int break_state)
  */
 static void atmel_rx_chars(struct uart_port *port)
 {
-	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *) port;
+	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
 	struct tty_struct *tty = port->info->tty;
 	unsigned int status, ch, flg;
 
@@ -266,10 +264,12 @@ static void atmel_rx_chars(struct uart_port *port)
 		if (unlikely(status & (ATMEL_US_PARE | ATMEL_US_FRAME
 				       | ATMEL_US_OVRE | ATMEL_US_RXBRK)
 			     || atmel_port->break_active)) {
-			UART_PUT_CR(port, ATMEL_US_RSTSTA);	/* clear error */
+			/* clear error */
+			UART_PUT_CR(port, ATMEL_US_RSTSTA);
 			if (status & ATMEL_US_RXBRK
 			    && !atmel_port->break_active) {
-				status &= ~(ATMEL_US_PARE | ATMEL_US_FRAME);	/* ignore side-effect */
+				/* ignore side-effect */
+				status &= ~(ATMEL_US_PARE | ATMEL_US_FRAME);
 				port->icount.brk++;
 				atmel_port->break_active = 1;
 				UART_PUT_IER(port, ATMEL_US_RXBRK);
@@ -309,7 +309,7 @@ static void atmel_rx_chars(struct uart_port *port)
 
 		uart_insert_char(port, status, ATMEL_US_OVRE, ch, flg);
 
-	ignore_char:
+ignore_char:
 		status = UART_GET_CSR(port);
 	}
 
@@ -350,44 +350,73 @@ static void atmel_tx_chars(struct uart_port *port)
 }
 
 /*
+ * receive interrupt handler.
+ */
+static void
+atmel_handle_receive(struct uart_port *port, unsigned int pending)
+{
+	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
+
+	/* Interrupt receive */
+	if (pending & ATMEL_US_RXRDY)
+		atmel_rx_chars(port);
+	else if (pending & ATMEL_US_RXBRK) {
+		/*
+		 * End of break detected. If it came along with a
+		 * character, atmel_rx_chars will handle it.
+		 */
+		UART_PUT_CR(port, ATMEL_US_RSTSTA);
+		UART_PUT_IDR(port, ATMEL_US_RXBRK);
+		atmel_port->break_active = 0;
+	}
+}
+
+/*
+ * transmit interrupt handler.
+ */
+static void
+atmel_handle_transmit(struct uart_port *port, unsigned int pending)
+{
+	/* Interrupt transmit */
+	if (pending & ATMEL_US_TXRDY)
+		atmel_tx_chars(port);
+}
+
+/*
+ * status flags interrupt handler.
+ */
+static void
+atmel_handle_status(struct uart_port *port, unsigned int pending,
+		    unsigned int status)
+{
+	/* TODO: All reads to CSR will clear these interrupts! */
+	if (pending & ATMEL_US_RIIC)
+		port->icount.rng++;
+	if (pending & ATMEL_US_DSRIC)
+		port->icount.dsr++;
+	if (pending & ATMEL_US_DCDIC)
+		uart_handle_dcd_change(port, !(status & ATMEL_US_DCD));
+	if (pending & ATMEL_US_CTSIC)
+		uart_handle_cts_change(port, !(status & ATMEL_US_CTS));
+	if (pending & (ATMEL_US_RIIC | ATMEL_US_DSRIC | ATMEL_US_DCDIC
+				| ATMEL_US_CTSIC))
+		wake_up_interruptible(&port->info->delta_msr_wait);
+}
+
+/*
  * Interrupt handler
  */
 static irqreturn_t atmel_interrupt(int irq, void *dev_id)
 {
 	struct uart_port *port = dev_id;
-	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *) port;
 	unsigned int status, pending, pass_counter = 0;
 
 	status = UART_GET_CSR(port);
 	pending = status & UART_GET_IMR(port);
 	while (pending) {
-		/* Interrupt receive */
-		if (pending & ATMEL_US_RXRDY)
-			atmel_rx_chars(port);
-		else if (pending & ATMEL_US_RXBRK) {
-			/*
-			 * End of break detected. If it came along
-			 * with a character, atmel_rx_chars will
-			 * handle it.
-			 */
-			UART_PUT_CR(port, ATMEL_US_RSTSTA);
-			UART_PUT_IDR(port, ATMEL_US_RXBRK);
-			atmel_port->break_active = 0;
-		}
-
-		// TODO: All reads to CSR will clear these interrupts!
-		if (pending & ATMEL_US_RIIC) port->icount.rng++;
-		if (pending & ATMEL_US_DSRIC) port->icount.dsr++;
-		if (pending & ATMEL_US_DCDIC)
-			uart_handle_dcd_change(port, !(status & ATMEL_US_DCD));
-		if (pending & ATMEL_US_CTSIC)
-			uart_handle_cts_change(port, !(status & ATMEL_US_CTS));
-		if (pending & (ATMEL_US_RIIC | ATMEL_US_DSRIC | ATMEL_US_DCDIC | ATMEL_US_CTSIC))
-			wake_up_interruptible(&port->info->delta_msr_wait);
-
-		/* Interrupt transmit */
-		if (pending & ATMEL_US_TXRDY)
-			atmel_tx_chars(port);
+		atmel_handle_receive(port, pending);
+		atmel_handle_status(port, pending, status);
+		atmel_handle_transmit(port, pending);
 
 		if (pass_counter++ > ATMEL_ISR_PASS_LIMIT)
 			break;
@@ -415,7 +444,8 @@ static int atmel_startup(struct uart_port *port)
 	/*
 	 * Allocate the IRQ
 	 */
-	retval = request_irq(port->irq, atmel_interrupt, IRQF_SHARED, "atmel_serial", port);
+	retval = request_irq(port->irq, atmel_interrupt, IRQF_SHARED,
+			"atmel_serial", port);
 	if (retval) {
 		printk("atmel_serial: atmel_startup - Can't get irq\n");
 		return retval;
@@ -437,9 +467,11 @@ static int atmel_startup(struct uart_port *port)
 	 * Finally, enable the serial port
 	 */
 	UART_PUT_CR(port, ATMEL_US_RSTSTA | ATMEL_US_RSTRX);
-	UART_PUT_CR(port, ATMEL_US_TXEN | ATMEL_US_RXEN);		/* enable xmit & rcvr */
+	/* enable xmit & rcvr */
+	UART_PUT_CR(port, ATMEL_US_TXEN | ATMEL_US_RXEN);
 
-	UART_PUT_IER(port, ATMEL_US_RXRDY);		/* enable receive only */
+	/* enable receive only */
+	UART_PUT_IER(port, ATMEL_US_RXRDY);
 
 	return 0;
 }
@@ -471,45 +503,48 @@ static void atmel_shutdown(struct uart_port *port)
 /*
  * Power / Clock management.
  */
-static void atmel_serial_pm(struct uart_port *port, unsigned int state, unsigned int oldstate)
+static void atmel_serial_pm(struct uart_port *port, unsigned int state,
+			    unsigned int oldstate)
 {
-	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *) port;
+	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
 
 	switch (state) {
-		case 0:
-			/*
-			 * Enable the peripheral clock for this serial port.
-			 * This is called on uart_open() or a resume event.
-			 */
-			clk_enable(atmel_port->clk);
-			break;
-		case 3:
-			/*
-			 * Disable the peripheral clock for this serial port.
-			 * This is called on uart_close() or a suspend event.
-			 */
-			clk_disable(atmel_port->clk);
-			break;
-		default:
-			printk(KERN_ERR "atmel_serial: unknown pm %d\n", state);
+	case 0:
+		/*
+		 * Enable the peripheral clock for this serial port.
+		 * This is called on uart_open() or a resume event.
+		 */
+		clk_enable(atmel_port->clk);
+		break;
+	case 3:
+		/*
+		 * Disable the peripheral clock for this serial port.
+		 * This is called on uart_close() or a suspend event.
+		 */
+		clk_disable(atmel_port->clk);
+		break;
+	default:
+		printk(KERN_ERR "atmel_serial: unknown pm %d\n", state);
 	}
 }
 
 /*
  * Change the port parameters
  */
-static void atmel_set_termios(struct uart_port *port, struct ktermios * termios, struct ktermios * old)
+static void atmel_set_termios(struct uart_port *port, struct ktermios *termios,
+			      struct ktermios *old)
 {
 	unsigned long flags;
 	unsigned int mode, imr, quot, baud;
 
 	/* Get current mode register */
-	mode = UART_GET_MR(port) & ~(ATMEL_US_USCLKS | ATMEL_US_CHRL | ATMEL_US_NBSTOP | ATMEL_US_PAR);
+	mode = UART_GET_MR(port) & ~(ATMEL_US_USCLKS | ATMEL_US_CHRL
+					| ATMEL_US_NBSTOP | ATMEL_US_PAR);
 
-	baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk/16);
+	baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk / 16);
 	quot = uart_get_divisor(port, baud);
 
-	if (quot > 65535) {		/* BRGR is 16-bit, so switch to slower clock */
+	if (quot > 65535) {	/* BRGR is 16-bit, so switch to slower clock */
 		quot /= 8;
 		mode |= ATMEL_US_USCLKS_MCK_DIV8;
 	}
@@ -536,18 +571,17 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios * termios,
 
 	/* parity */
 	if (termios->c_cflag & PARENB) {
-		if (termios->c_cflag & CMSPAR) {			/* Mark or Space parity */
+		/* Mark or Space parity */
+		if (termios->c_cflag & CMSPAR) {
 			if (termios->c_cflag & PARODD)
 				mode |= ATMEL_US_PAR_MARK;
 			else
 				mode |= ATMEL_US_PAR_SPACE;
-		}
-		else if (termios->c_cflag & PARODD)
+		} else if (termios->c_cflag & PARODD)
 			mode |= ATMEL_US_PAR_ODD;
 		else
 			mode |= ATMEL_US_PAR_EVEN;
-	}
-	else
+	} else
 		mode |= ATMEL_US_PAR_NONE;
 
 	spin_lock_irqsave(&port->lock, flags);
@@ -573,16 +607,16 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios * termios,
 		if (termios->c_iflag & IGNPAR)
 			port->ignore_status_mask |= ATMEL_US_OVRE;
 	}
-
-	// TODO: Ignore all characters if CREAD is set.
+	/* TODO: Ignore all characters if CREAD is set.*/
 
 	/* update the per-port timeout */
 	uart_update_timeout(port, termios->c_cflag, baud);
 
-	/* disable interrupts and drain transmitter */
-	imr = UART_GET_IMR(port);	/* get interrupt mask */
-	UART_PUT_IDR(port, -1);		/* disable all interrupts */
-	while (!(UART_GET_CSR(port) & ATMEL_US_TXEMPTY)) { barrier(); }
+	/* save/disable interrupts and drain transmitter */
+	imr = UART_GET_IMR(port);
+	UART_PUT_IDR(port, -1);
+	while (!(UART_GET_CSR(port) & ATMEL_US_TXEMPTY))
+		barrier();
 
 	/* disable receiver and transmitter */
 	UART_PUT_CR(port, ATMEL_US_TXDIS | ATMEL_US_RXDIS);
@@ -708,7 +742,8 @@ static struct uart_ops atmel_pops = {
 /*
  * Configure the port from the platform device resource info.
  */
-static void __devinit atmel_init_port(struct atmel_uart_port *atmel_port, struct platform_device *pdev)
+static void __devinit atmel_init_port(struct atmel_uart_port *atmel_port,
+				      struct platform_device *pdev)
 {
 	struct uart_port *port = &atmel_port->uart;
 	struct atmel_uart_data *data = pdev->dev.platform_data;
@@ -731,7 +766,8 @@ static void __devinit atmel_init_port(struct atmel_uart_port *atmel_port, struct
 		port->membase	= NULL;
 	}
 
-	if (!atmel_port->clk) {		/* for console, the clock could already be configured */
+	/* for console, the clock could already be configured */
+	if (!atmel_port->clk) {
 		atmel_port->clk = clk_get(&pdev->dev, "usart");
 		clk_enable(atmel_port->clk);
 		port->uartclk = clk_get_rate(atmel_port->clk);
@@ -755,7 +791,6 @@ void __init atmel_register_uart_fns(struct atmel_port_fns *fns)
 	atmel_pops.set_wake	= fns->set_wake;
 }
 
-
 #ifdef CONFIG_SERIAL_ATMEL_CONSOLE
 static void atmel_console_putchar(struct uart_port *port, int ch)
 {
@@ -773,28 +808,30 @@ static void atmel_console_write(struct console *co, const char *s, u_int count)
 	unsigned int status, imr;
 
 	/*
-	 *	First, save IMR and then disable interrupts
+	 * First, save IMR and then disable interrupts
 	 */
-	imr = UART_GET_IMR(port);	/* get interrupt mask */
+	imr = UART_GET_IMR(port);
 	UART_PUT_IDR(port, ATMEL_US_RXRDY | ATMEL_US_TXRDY);
 
 	uart_console_write(port, s, count, atmel_console_putchar);
 
 	/*
-	 *	Finally, wait for transmitter to become empty
-	 *	and restore IMR
+	 * Finally, wait for transmitter to become empty
+	 * and restore IMR
 	 */
 	do {
 		status = UART_GET_CSR(port);
 	} while (!(status & ATMEL_US_TXRDY));
-	UART_PUT_IER(port, imr);	/* set interrupts back the way they were */
+	/* set interrupts back the way they were */
+	UART_PUT_IER(port, imr);
 }
 
 /*
- * If the port was already initialised (eg, by a boot loader), try to determine
- * the current setup.
+ * If the port was already initialised (eg, by a boot loader),
+ * try to determine the current setup.
  */
-static void __init atmel_console_get_options(struct uart_port *port, int *baud, int *parity, int *bits)
+static void __init atmel_console_get_options(struct uart_port *port, int *baud,
+					     int *parity, int *bits)
 {
 	unsigned int mr, quot;
 
@@ -836,10 +873,12 @@ static int __init atmel_console_setup(struct console *co, char *options)
 	int parity = 'n';
 	int flow = 'n';
 
-	if (port->membase == 0)		/* Port not initialized yet - delay setup */
+	if (port->membase == NULL) {
+		/* Port not initialized yet - delay setup */
 		return -ENODEV;
+	}
 
-	UART_PUT_IDR(port, -1);				/* disable interrupts */
+	UART_PUT_IDR(port, -1);
 	UART_PUT_CR(port, ATMEL_US_RSTSTA | ATMEL_US_RSTRX);
 	UART_PUT_CR(port, ATMEL_US_TXEN | ATMEL_US_RXEN);
 
@@ -871,13 +910,16 @@ static struct console atmel_console = {
 static int __init atmel_console_init(void)
 {
 	if (atmel_default_console_device) {
-		add_preferred_console(ATMEL_DEVICENAME, atmel_default_console_device->id, NULL);
-		atmel_init_port(&(atmel_ports[atmel_default_console_device->id]), atmel_default_console_device);
+		add_preferred_console(ATMEL_DEVICENAME,
+				      atmel_default_console_device->id, NULL);
+		atmel_init_port(&atmel_ports[atmel_default_console_device->id],
+				atmel_default_console_device);
 		register_console(&atmel_console);
 	}
 
 	return 0;
 }
+
 console_initcall(atmel_console_init);
 
 /*
@@ -885,11 +927,13 @@ console_initcall(atmel_console_init);
  */
 static int __init atmel_late_console_init(void)
 {
-	if (atmel_default_console_device && !(atmel_console.flags & CON_ENABLED))
+	if (atmel_default_console_device
+	    && !(atmel_console.flags & CON_ENABLED))
 		register_console(&atmel_console);
 
 	return 0;
 }
+
 core_initcall(atmel_late_console_init);
 
 #else
@@ -897,22 +941,24 @@ core_initcall(atmel_late_console_init);
 #endif
 
 static struct uart_driver atmel_uart = {
-	.owner			= THIS_MODULE,
-	.driver_name		= "atmel_serial",
-	.dev_name		= ATMEL_DEVICENAME,
-	.major			= SERIAL_ATMEL_MAJOR,
-	.minor			= MINOR_START,
-	.nr			= ATMEL_MAX_UART,
-	.cons			= ATMEL_CONSOLE_DEVICE,
+	.owner		= THIS_MODULE,
+	.driver_name	= "atmel_serial",
+	.dev_name	= ATMEL_DEVICENAME,
+	.major		= SERIAL_ATMEL_MAJOR,
+	.minor		= MINOR_START,
+	.nr		= ATMEL_MAX_UART,
+	.cons		= ATMEL_CONSOLE_DEVICE,
 };
 
 #ifdef CONFIG_PM
-static int atmel_serial_suspend(struct platform_device *pdev, pm_message_t state)
+static int atmel_serial_suspend(struct platform_device *pdev,
+				pm_message_t state)
 {
 	struct uart_port *port = platform_get_drvdata(pdev);
-	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *) port;
+	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
 
-	if (device_may_wakeup(&pdev->dev) && !at91_suspend_entering_slow_clock())
+	if (device_may_wakeup(&pdev->dev)
+	    && !at91_suspend_entering_slow_clock())
 		enable_irq_wake(port->irq);
 	else {
 		uart_suspend_port(&atmel_uart, port);
@@ -925,13 +971,12 @@ static int atmel_serial_suspend(struct platform_device *pdev, pm_message_t state
 static int atmel_serial_resume(struct platform_device *pdev)
 {
 	struct uart_port *port = platform_get_drvdata(pdev);
-	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *) port;
+	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
 
 	if (atmel_port->suspended) {
 		uart_resume_port(&atmel_uart, port);
 		atmel_port->suspended = 0;
-	}
-	else
+	} else
 		disable_irq_wake(port->irq);
 
 	return 0;
@@ -961,7 +1006,7 @@ static int __devinit atmel_serial_probe(struct platform_device *pdev)
 static int __devexit atmel_serial_remove(struct platform_device *pdev)
 {
 	struct uart_port *port = platform_get_drvdata(pdev);
-	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *) port;
+	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
 	int ret = 0;
 
 	clk_disable(atmel_port->clk);
-- 
1.5.3.8

[PATCH -mm v4 3/9] atmel_serial: Use cpu_relax() when busy-waiting

[Haavard Skinnemoen]

Replace two instances of barrier() with cpu_relax() since that's the
right thing to do when busy-waiting. This does not actually change
anything since cpu_relax() is defined as barrier() on both ARM and
AVR32.

Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Acked-by: Andrew Victor <linux@maxim.org.za>
---
 drivers/serial/atmel_serial.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/serial/atmel_serial.c b/drivers/serial/atmel_serial.c
index ee5d844..4b5c6ff 100644
--- a/drivers/serial/atmel_serial.c
+++ b/drivers/serial/atmel_serial.c
@@ -616,7 +616,7 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios,
 	imr = UART_GET_IMR(port);
 	UART_PUT_IDR(port, -1);
 	while (!(UART_GET_CSR(port) & ATMEL_US_TXEMPTY))
-		barrier();
+		cpu_relax();
 
 	/* disable receiver and transmitter */
 	UART_PUT_CR(port, ATMEL_US_TXDIS | ATMEL_US_RXDIS);
@@ -795,7 +795,7 @@ void __init atmel_register_uart_fns(struct atmel_port_fns *fns)
 static void atmel_console_putchar(struct uart_port *port, int ch)
 {
 	while (!(UART_GET_CSR(port) & ATMEL_US_TXRDY))
-		barrier();
+		cpu_relax();
 	UART_PUT_CHAR(port, ch);
 }
 
-- 
1.5.3.8

[PATCH -mm v4 4/9] atmel_serial: Use existing console options only if BRG is running

[Haavard Skinnemoen]

If BRGR is zero, the baud rate generator isn't running, so the boot
loader can't have initialized the port.

Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Acked-by: Andrew Victor <linux@maxim.org.za>
---
 drivers/serial/atmel_serial.c |   15 +++++++--------
 1 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/drivers/serial/atmel_serial.c b/drivers/serial/atmel_serial.c
index 4b5c6ff..746aea0 100644
--- a/drivers/serial/atmel_serial.c
+++ b/drivers/serial/atmel_serial.c
@@ -835,13 +835,13 @@ static void __init atmel_console_get_options(struct uart_port *port, int *baud,
 {
 	unsigned int mr, quot;
 
-// TODO: CR is a write-only register
-//	unsigned int cr;
-//
-//	cr = UART_GET_CR(port) & (ATMEL_US_RXEN | ATMEL_US_TXEN);
-//	if (cr == (ATMEL_US_RXEN | ATMEL_US_TXEN)) {
-//		/* ok, the port was enabled */
-//	}
+	/*
+	 * If the baud rate generator isn't running, the port wasn't
+	 * initialized by the boot loader.
+	 */
+	quot = UART_GET_BRGR(port);
+	if (!quot)
+		return;
 
 	mr = UART_GET_MR(port) & ATMEL_US_CHRL;
 	if (mr == ATMEL_US_CHRL_8)
@@ -861,7 +861,6 @@ static void __init atmel_console_get_options(struct uart_port *port, int *baud,
 	 * lower than one of those, as it would make us fall through
 	 * to a much lower baud rate than we really want.
 	 */
-	quot = UART_GET_BRGR(port);
 	*baud = port->uartclk / (16 * (quot - 1));
 }
 
-- 
1.5.3.8

[PATCH -mm v4 5/9] atmel_serial: Fix bugs in probe() error path and remove()

[Haavard Skinnemoen]

When an error happens in probe(), the clocks should be disabled, but
only if the port isn't already used as a console.

In remove(), the port struct shouldn't be freed because it's defined
statically.

Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
---
 drivers/serial/atmel_serial.c |   39 +++++++++++++++++++++++++++++----------
 1 files changed, 29 insertions(+), 10 deletions(-)

diff --git a/drivers/serial/atmel_serial.c b/drivers/serial/atmel_serial.c
index 746aea0..0e715f4 100644
--- a/drivers/serial/atmel_serial.c
+++ b/drivers/serial/atmel_serial.c
@@ -935,8 +935,18 @@ static int __init atmel_late_console_init(void)
 
 core_initcall(atmel_late_console_init);
 
+static inline bool atmel_is_console_port(struct uart_port *port)
+{
+	return port->cons && port->cons->index == port->line;
+}
+
 #else
 #define ATMEL_CONSOLE_DEVICE	NULL
+
+static inline bool atmel_is_console_port(struct uart_port *port)
+{
+	return false;
+}
 #endif
 
 static struct uart_driver atmel_uart = {
@@ -994,9 +1004,19 @@ static int __devinit atmel_serial_probe(struct platform_device *pdev)
 	atmel_init_port(port, pdev);
 
 	ret = uart_add_one_port(&atmel_uart, &port->uart);
-	if (!ret) {
-		device_init_wakeup(&pdev->dev, 1);
-		platform_set_drvdata(pdev, port);
+	if (ret)
+		goto err_add_port;
+
+	device_init_wakeup(&pdev->dev, 1);
+	platform_set_drvdata(pdev, port);
+
+	return 0;
+
+err_add_port:
+	if (!atmel_is_console_port(&port->uart)) {
+		clk_disable(port->clk);
+		clk_put(port->clk);
+		port->clk = NULL;
 	}
 
 	return ret;
@@ -1008,16 +1028,15 @@ static int __devexit atmel_serial_remove(struct platform_device *pdev)
 	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
 	int ret = 0;
 
-	clk_disable(atmel_port->clk);
-	clk_put(atmel_port->clk);
-
 	device_init_wakeup(&pdev->dev, 0);
 	platform_set_drvdata(pdev, NULL);
 
-	if (port) {
-		ret = uart_remove_one_port(&atmel_uart, port);
-		kfree(port);
-	}
+	ret = uart_remove_one_port(&atmel_uart, port);
+
+	/* "port" is allocated statically, so we shouldn't free it */
+
+	clk_disable(atmel_port->clk);
+	clk_put(atmel_port->clk);
 
 	return ret;
 }
-- 
1.5.3.8

[PATCH -mm v4 6/9] atmel_serial: Split the interrupt handler

[Haavard Skinnemoen]

From: Remy Bohmer <linux@bohmer.net>

This patch splits up the interrupt handler of the serial port
into a interrupt top-half and a tasklet.

The goal is to get the interrupt top-half as short as possible to
minimize latencies on interrupts. But the old code also does some
calls in the interrupt handler that are not allowed on preempt-RT
in IRQF_NODELAY context. This handler is executed in this context
because of the interrupt sharing with the timer interrupt.
The timer interrupt on Preempt-RT runs in IRQF_NODELAY context.

The tasklet takes care of handling control status changes, pushing
incoming characters to the tty layer, handling break and other errors.
It also handles pushing TX data into the data register.

Reading the complete receive queue is still done in the top-half
because we never want to miss any incoming character.

[hskinnemoen@atmel.com: misc cleanups and simplifications]
Signed-off-by: Remy Bohmer <linux@bohmer.net>
Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
---
 drivers/serial/atmel_serial.c |  245 +++++++++++++++++++++++++++++++---------
 1 files changed, 190 insertions(+), 55 deletions(-)

diff --git a/drivers/serial/atmel_serial.c b/drivers/serial/atmel_serial.c
index 0e715f4..0e65e98 100644
--- a/drivers/serial/atmel_serial.c
+++ b/drivers/serial/atmel_serial.c
@@ -104,6 +104,13 @@
 static int (*atmel_open_hook)(struct uart_port *);
 static void (*atmel_close_hook)(struct uart_port *);
 
+struct atmel_uart_char {
+	u16		status;
+	u16		ch;
+};
+
+#define ATMEL_SERIAL_RINGSIZE 1024
+
 /*
  * We wrap our port structure around the generic uart_port.
  */
@@ -112,6 +119,12 @@ struct atmel_uart_port {
 	struct clk		*clk;		/* uart clock */
 	unsigned short		suspended;	/* is port suspended? */
 	int			break_active;	/* break being received */
+
+	struct tasklet_struct	tasklet;
+	unsigned int		irq_status;
+	unsigned int		irq_status_prev;
+
+	struct circ_buf		rx_ring;
 };
 
 static struct atmel_uart_port atmel_ports[ATMEL_MAX_UART];
@@ -241,22 +254,42 @@ static void atmel_break_ctl(struct uart_port *port, int break_state)
 }
 
 /*
+ * Stores the incoming character in the ring buffer
+ */
+static void
+atmel_buffer_rx_char(struct uart_port *port, unsigned int status,
+		     unsigned int ch)
+{
+	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
+	struct circ_buf *ring = &atmel_port->rx_ring;
+	struct atmel_uart_char *c;
+
+	if (!CIRC_SPACE(ring->head, ring->tail, ATMEL_SERIAL_RINGSIZE))
+		/* Buffer overflow, ignore char */
+		return;
+
+	c = &((struct atmel_uart_char *)ring->buf)[ring->head];
+	c->status	= status;
+	c->ch		= ch;
+
+	/* Make sure the character is stored before we update head. */
+	smp_wmb();
+
+	ring->head = (ring->head + 1) & (ATMEL_SERIAL_RINGSIZE - 1);
+}
+
+/*
  * Characters received (called from interrupt handler)
  */
 static void atmel_rx_chars(struct uart_port *port)
 {
 	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
-	struct tty_struct *tty = port->info->tty;
-	unsigned int status, ch, flg;
+	unsigned int status, ch;
 
 	status = UART_GET_CSR(port);
 	while (status & ATMEL_US_RXRDY) {
 		ch = UART_GET_CHAR(port);
 
-		port->icount.rx++;
-
-		flg = TTY_NORMAL;
-
 		/*
 		 * note that the error handling code is
 		 * out of the main execution path
@@ -264,17 +297,14 @@ static void atmel_rx_chars(struct uart_port *port)
 		if (unlikely(status & (ATMEL_US_PARE | ATMEL_US_FRAME
 				       | ATMEL_US_OVRE | ATMEL_US_RXBRK)
 			     || atmel_port->break_active)) {
+
 			/* clear error */
 			UART_PUT_CR(port, ATMEL_US_RSTSTA);
+
 			if (status & ATMEL_US_RXBRK
 			    && !atmel_port->break_active) {
-				/* ignore side-effect */
-				status &= ~(ATMEL_US_PARE | ATMEL_US_FRAME);
-				port->icount.brk++;
 				atmel_port->break_active = 1;
 				UART_PUT_IER(port, ATMEL_US_RXBRK);
-				if (uart_handle_break(port))
-					goto ignore_char;
 			} else {
 				/*
 				 * This is either the end-of-break
@@ -287,52 +317,30 @@ static void atmel_rx_chars(struct uart_port *port)
 				status &= ~ATMEL_US_RXBRK;
 				atmel_port->break_active = 0;
 			}
-			if (status & ATMEL_US_PARE)
-				port->icount.parity++;
-			if (status & ATMEL_US_FRAME)
-				port->icount.frame++;
-			if (status & ATMEL_US_OVRE)
-				port->icount.overrun++;
-
-			status &= port->read_status_mask;
-
-			if (status & ATMEL_US_RXBRK)
-				flg = TTY_BREAK;
-			else if (status & ATMEL_US_PARE)
-				flg = TTY_PARITY;
-			else if (status & ATMEL_US_FRAME)
-				flg = TTY_FRAME;
 		}
 
-		if (uart_handle_sysrq_char(port, ch))
-			goto ignore_char;
-
-		uart_insert_char(port, status, ATMEL_US_OVRE, ch, flg);
-
-ignore_char:
+		atmel_buffer_rx_char(port, status, ch);
 		status = UART_GET_CSR(port);
 	}
 
-	tty_flip_buffer_push(tty);
+	tasklet_schedule(&atmel_port->tasklet);
 }
 
 /*
- * Transmit characters (called from interrupt handler)
+ * Transmit characters (called from tasklet with TXRDY interrupt
+ * disabled)
  */
 static void atmel_tx_chars(struct uart_port *port)
 {
 	struct circ_buf *xmit = &port->info->xmit;
 
-	if (port->x_char) {
+	if (port->x_char && UART_GET_CSR(port) & ATMEL_US_TXRDY) {
 		UART_PUT_CHAR(port, port->x_char);
 		port->icount.tx++;
 		port->x_char = 0;
-		return;
 	}
-	if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
-		atmel_stop_tx(port);
+	if (uart_circ_empty(xmit) || uart_tx_stopped(port))
 		return;
-	}
 
 	while (UART_GET_CSR(port) & ATMEL_US_TXRDY) {
 		UART_PUT_CHAR(port, xmit->buf[xmit->tail]);
@@ -345,8 +353,8 @@ static void atmel_tx_chars(struct uart_port *port)
 	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
 		uart_write_wakeup(port);
 
-	if (uart_circ_empty(xmit))
-		atmel_stop_tx(port);
+	if (!uart_circ_empty(xmit))
+		UART_PUT_IER(port, ATMEL_US_TXRDY);
 }
 
 /*
@@ -372,14 +380,18 @@ atmel_handle_receive(struct uart_port *port, unsigned int pending)
 }
 
 /*
- * transmit interrupt handler.
+ * transmit interrupt handler. (Transmit is IRQF_NODELAY safe)
  */
 static void
 atmel_handle_transmit(struct uart_port *port, unsigned int pending)
 {
+	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
+
 	/* Interrupt transmit */
-	if (pending & ATMEL_US_TXRDY)
-		atmel_tx_chars(port);
+	if (pending & ATMEL_US_TXRDY) {
+		UART_PUT_IDR(port, ATMEL_US_TXRDY);
+		tasklet_schedule(&atmel_port->tasklet);
+	}
 }
 
 /*
@@ -389,18 +401,13 @@ static void
 atmel_handle_status(struct uart_port *port, unsigned int pending,
 		    unsigned int status)
 {
-	/* TODO: All reads to CSR will clear these interrupts! */
-	if (pending & ATMEL_US_RIIC)
-		port->icount.rng++;
-	if (pending & ATMEL_US_DSRIC)
-		port->icount.dsr++;
-	if (pending & ATMEL_US_DCDIC)
-		uart_handle_dcd_change(port, !(status & ATMEL_US_DCD));
-	if (pending & ATMEL_US_CTSIC)
-		uart_handle_cts_change(port, !(status & ATMEL_US_CTS));
+	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
+
 	if (pending & (ATMEL_US_RIIC | ATMEL_US_DSRIC | ATMEL_US_DCDIC
-				| ATMEL_US_CTSIC))
-		wake_up_interruptible(&port->info->delta_msr_wait);
+				| ATMEL_US_CTSIC)) {
+		atmel_port->irq_status = status;
+		tasklet_schedule(&atmel_port->tasklet);
+	}
 }
 
 /*
@@ -427,6 +434,114 @@ static irqreturn_t atmel_interrupt(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
+static void atmel_rx_from_ring(struct uart_port *port)
+{
+	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
+	struct circ_buf *ring = &atmel_port->rx_ring;
+	unsigned int flg;
+	unsigned int status;
+
+	while (ring->head != ring->tail) {
+		struct atmel_uart_char c;
+
+		/* Make sure c is loaded after head. */
+		smp_rmb();
+
+		c = ((struct atmel_uart_char *)ring->buf)[ring->tail];
+
+		ring->tail = (ring->tail + 1) & (ATMEL_SERIAL_RINGSIZE - 1);
+
+		port->icount.rx++;
+		status = c.status;
+		flg = TTY_NORMAL;
+
+		/*
+		 * note that the error handling code is
+		 * out of the main execution path
+		 */
+		if (unlikely(status & (ATMEL_US_PARE | ATMEL_US_FRAME
+				       | ATMEL_US_OVRE | ATMEL_US_RXBRK))) {
+			if (status & ATMEL_US_RXBRK) {
+				/* ignore side-effect */
+				status &= ~(ATMEL_US_PARE | ATMEL_US_FRAME);
+
+				port->icount.brk++;
+				if (uart_handle_break(port))
+					continue;
+			}
+			if (status & ATMEL_US_PARE)
+				port->icount.parity++;
+			if (status & ATMEL_US_FRAME)
+				port->icount.frame++;
+			if (status & ATMEL_US_OVRE)
+				port->icount.overrun++;
+
+			status &= port->read_status_mask;
+
+			if (status & ATMEL_US_RXBRK)
+				flg = TTY_BREAK;
+			else if (status & ATMEL_US_PARE)
+				flg = TTY_PARITY;
+			else if (status & ATMEL_US_FRAME)
+				flg = TTY_FRAME;
+		}
+
+
+		if (uart_handle_sysrq_char(port, c.ch))
+			continue;
+
+		uart_insert_char(port, status, ATMEL_US_OVRE, c.ch, flg);
+	}
+
+	/*
+	 * Drop the lock here since it might end up calling
+	 * uart_start(), which takes the lock.
+	 */
+	spin_unlock(&port->lock);
+	tty_flip_buffer_push(port->info->tty);
+	spin_lock(&port->lock);
+}
+
+/*
+ * tasklet handling tty stuff outside the interrupt handler.
+ */
+static void atmel_tasklet_func(unsigned long data)
+{
+	struct uart_port *port = (struct uart_port *)data;
+	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
+	unsigned int status;
+	unsigned int status_change;
+
+	/* The interrupt handler does not take the lock */
+	spin_lock(&port->lock);
+
+	atmel_tx_chars(port);
+
+	status = atmel_port->irq_status;
+	status_change = status ^ atmel_port->irq_status_prev;
+
+	if (status_change & (ATMEL_US_RI | ATMEL_US_DSR
+				| ATMEL_US_DCD | ATMEL_US_CTS)) {
+		/* TODO: All reads to CSR will clear these interrupts! */
+		if (status_change & ATMEL_US_RI)
+			port->icount.rng++;
+		if (status_change & ATMEL_US_DSR)
+			port->icount.dsr++;
+		if (status_change & ATMEL_US_DCD)
+			uart_handle_dcd_change(port, !(status & ATMEL_US_DCD));
+		if (status_change & ATMEL_US_CTS)
+			uart_handle_cts_change(port, !(status & ATMEL_US_CTS));
+
+		wake_up_interruptible(&port->info->delta_msr_wait);
+
+		atmel_port->irq_status_prev = status;
+	}
+
+	atmel_rx_from_ring(port);
+
+	spin_unlock(&port->lock);
+}
+
 /*
  * Perform initialization and enable port for reception
  */
@@ -758,6 +873,11 @@ static void __devinit atmel_init_port(struct atmel_uart_port *atmel_port,
 	port->mapbase	= pdev->resource[0].start;
 	port->irq	= pdev->resource[1].start;
 
+	tasklet_init(&atmel_port->tasklet, atmel_tasklet_func,
+			(unsigned long)port);
+
+	memset(&atmel_port->rx_ring, 0, sizeof(atmel_port->rx_ring));
+
 	if (data->regs)
 		/* Already mapped by setup code */
 		port->membase = data->regs;
@@ -998,11 +1118,20 @@ static int atmel_serial_resume(struct platform_device *pdev)
 static int __devinit atmel_serial_probe(struct platform_device *pdev)
 {
 	struct atmel_uart_port *port;
+	void *data;
 	int ret;
 
+	BUILD_BUG_ON(!is_power_of_2(ATMEL_SERIAL_RINGSIZE));
+
 	port = &atmel_ports[pdev->id];
 	atmel_init_port(port, pdev);
 
+	ret = -ENOMEM;
+	data = kmalloc(ATMEL_SERIAL_RINGSIZE, GFP_KERNEL);
+	if (!data)
+		goto err_alloc_ring;
+	port->rx_ring.buf = data;
+
 	ret = uart_add_one_port(&atmel_uart, &port->uart);
 	if (ret)
 		goto err_add_port;
@@ -1013,6 +1142,9 @@ static int __devinit atmel_serial_probe(struct platform_device *pdev)
 	return 0;
 
 err_add_port:
+	kfree(port->rx_ring.buf);
+	port->rx_ring.buf = NULL;
+err_alloc_ring:
 	if (!atmel_is_console_port(&port->uart)) {
 		clk_disable(port->clk);
 		clk_put(port->clk);
@@ -1033,6 +1165,9 @@ static int __devexit atmel_serial_remove(struct platform_device *pdev)
 
 	ret = uart_remove_one_port(&atmel_uart, port);
 
+	tasklet_kill(&atmel_port->tasklet);
+	kfree(atmel_port->rx_ring.buf);
+
 	/* "port" is allocated statically, so we shouldn't free it */
 
 	clk_disable(atmel_port->clk);
-- 
1.5.3.8

[PATCH -mm v4 7/9] atmel_serial: Add DMA support

[Haavard Skinnemoen]

From: Chip Coldwell <coldwell@redhat.com>

This patch is based on the DMA-patch by Chip Coldwell for the
AT91/AT32 serial USARTS, with some tweaks to make it apply neatly on
top of the other patches in this series.

The RX and TX code has been moved to a tasklet and reworked a bit.
Instead of depending on the ENDRX and TIMEOUT bits in CSR, we simply
grab as much data as we can from the DMA buffers. I think this closes
a race where the ENDRX bit is set after we read CSR but before we read
RPR, although I haven't confirmed this.

Similarly, the two TX handlers (ENDTX and TXBUFE) have been combined
into one. Since the current code only uses a single TX buffer, there's
no point in handling those interrupts separately.

This also fixes a DMA sync bug in the original patch.

[linux@bohmer.net: rebased onto irq-splitup patch]
[hskinnemoen@atmel.com: moved to tasklet, fixed dma bug, misc cleanups]
Signed-off-by: Remy Bohmer <linux@bohmer.net>
Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
---
 drivers/serial/Kconfig        |   15 ++
 drivers/serial/atmel_serial.c |  393 ++++++++++++++++++++++++++++++++++++++---
 2 files changed, 384 insertions(+), 24 deletions(-)

diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index d7e1996..67bfbb0 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -380,6 +380,21 @@ config SERIAL_ATMEL_CONSOLE
 	  console is the device which receives all kernel messages and
 	  warnings and which allows logins in single user mode).
 
+config SERIAL_ATMEL_PDC
+	bool "Support DMA transfers on AT91 / AT32 serial port"
+	depends on SERIAL_ATMEL
+	default y
+	help
+	  Say Y here if you wish to use the PDC to do DMA transfers to
+	  and from the Atmel AT91 / AT32 serial port. In order to
+	  actually use DMA transfers, make sure that the use_dma_tx
+	  and use_dma_rx members in the atmel_uart_data struct is set
+	  appropriately for each port.
+
+	  Note that break and error handling currently doesn't work
+	  properly when DMA is enabled. Make sure that ports where
+	  this matters don't use DMA.
+
 config SERIAL_ATMEL_TTYAT
 	bool "Install as device ttyATn instead of ttySn"
 	depends on SERIAL_ATMEL=y
diff --git a/drivers/serial/atmel_serial.c b/drivers/serial/atmel_serial.c
index 0e65e98..e4f9449 100644
--- a/drivers/serial/atmel_serial.c
+++ b/drivers/serial/atmel_serial.c
@@ -7,6 +7,8 @@
  *  Based on drivers/char/serial_sa1100.c, by Deep Blue Solutions Ltd.
  *  Based on drivers/char/serial.c, by Linus Torvalds, Theodore Ts'o.
  *
+ *  DMA support added by Chip Coldwell.
+ *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
@@ -33,6 +35,7 @@
 #include <linux/sysrq.h>
 #include <linux/tty_flip.h>
 #include <linux/platform_device.h>
+#include <linux/dma-mapping.h>
 #include <linux/atmel_pdc.h>
 
 #include <asm/io.h>
@@ -47,6 +50,10 @@
 
 #include "atmel_serial.h"
 
+#define PDC_BUFFER_SIZE		512
+/* Revisit: We should calculate this based on the actual port settings */
+#define PDC_RX_TIMEOUT		(3 * 10)		/* 3 bytes */
+
 #if defined(CONFIG_SERIAL_ATMEL_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
 #define SUPPORT_SYSRQ
 #endif
@@ -104,6 +111,13 @@
 static int (*atmel_open_hook)(struct uart_port *);
 static void (*atmel_close_hook)(struct uart_port *);
 
+struct atmel_dma_buffer {
+	unsigned char	*buf;
+	dma_addr_t	dma_addr;
+	size_t		dma_size;
+	unsigned int	ofs;
+};
+
 struct atmel_uart_char {
 	u16		status;
 	u16		ch;
@@ -120,6 +134,13 @@ struct atmel_uart_port {
 	unsigned short		suspended;	/* is port suspended? */
 	int			break_active;	/* break being received */
 
+	short			use_dma_rx;	/* enable PDC receiver */
+	short			pdc_rx_idx;	/* current PDC RX buffer */
+	struct atmel_dma_buffer	pdc_rx[2];	/* PDC receier */
+
+	short			use_dma_tx;	/* enable PDC transmitter */
+	struct atmel_dma_buffer	pdc_tx;		/* PDC transmitter */
+
 	struct tasklet_struct	tasklet;
 	unsigned int		irq_status;
 	unsigned int		irq_status_prev;
@@ -129,10 +150,39 @@ struct atmel_uart_port {
 
 static struct atmel_uart_port atmel_ports[ATMEL_MAX_UART];
 
+#define PDC_RX_BUF(port)	&(port)->pdc_rx[(port)->pdc_rx_idx]
+#define PDC_RX_SWITCH(port)	(port)->pdc_rx_idx = !(port)->pdc_rx_idx
+
 #ifdef SUPPORT_SYSRQ
 static struct console atmel_console;
 #endif
 
+#ifdef CONFIG_SERIAL_ATMEL_PDC
+static bool atmel_use_dma_rx(struct uart_port *port)
+{
+	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
+
+	return atmel_port->use_dma_rx;
+}
+
+static bool atmel_use_dma_tx(struct uart_port *port)
+{
+	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
+
+	return atmel_port->use_dma_tx;
+}
+#else
+static bool atmel_use_dma_rx(struct uart_port *port)
+{
+	return false;
+}
+
+static bool atmel_use_dma_tx(struct uart_port *port)
+{
+	return false;
+}
+#endif
+
 /*
  * Return TIOCSER_TEMT when transmitter FIFO and Shift register is empty.
  */
@@ -214,7 +264,12 @@ static u_int atmel_get_mctrl(struct uart_port *port)
  */
 static void atmel_stop_tx(struct uart_port *port)
 {
-	UART_PUT_IDR(port, ATMEL_US_TXRDY);
+	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);
 }
 
 /*
@@ -222,7 +277,17 @@ static void atmel_stop_tx(struct uart_port *port)
  */
 static void atmel_start_tx(struct uart_port *port)
 {
-	UART_PUT_IER(port, ATMEL_US_TXRDY);
+	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);
+		/* re-enable PDC transmit */
+		UART_PUT_PTCR(port, ATMEL_PDC_TXTEN);
+	} else
+		UART_PUT_IER(port, ATMEL_US_TXRDY);
 }
 
 /*
@@ -230,7 +295,12 @@ static void atmel_start_tx(struct uart_port *port)
  */
 static void atmel_stop_rx(struct uart_port *port)
 {
-	UART_PUT_IDR(port, ATMEL_US_RXRDY);
+	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_RXRDY);
 }
 
 /*
@@ -279,6 +349,27 @@ atmel_buffer_rx_char(struct uart_port *port, unsigned int status,
 }
 
 /*
+ * Deal with parity, framing and overrun errors.
+ */
+static void atmel_pdc_rxerr(struct uart_port *port, unsigned int status)
+{
+	/* clear error */
+	UART_PUT_CR(port, ATMEL_US_RSTSTA);
+
+	if (status & ATMEL_US_RXBRK) {
+		/* ignore side-effect */
+		status &= ~(ATMEL_US_PARE | ATMEL_US_FRAME);
+		port->icount.brk++;
+	}
+	if (status & ATMEL_US_PARE)
+		port->icount.parity++;
+	if (status & ATMEL_US_FRAME)
+		port->icount.frame++;
+	if (status & ATMEL_US_OVRE)
+		port->icount.overrun++;
+}
+
+/*
  * Characters received (called from interrupt handler)
  */
 static void atmel_rx_chars(struct uart_port *port)
@@ -365,6 +456,25 @@ atmel_handle_receive(struct uart_port *port, unsigned int pending)
 {
 	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
 
+	if (atmel_use_dma_rx(port)) {
+		/*
+		 * PDC receive. Just schedule the tasklet and let it
+		 * figure out the details.
+		 *
+		 * TODO: We're not handling error flags correctly at
+		 * the moment.
+		 */
+		if (pending & (ATMEL_US_ENDRX | ATMEL_US_TIMEOUT)) {
+			UART_PUT_IDR(port, (ATMEL_US_ENDRX
+						| ATMEL_US_TIMEOUT));
+			tasklet_schedule(&atmel_port->tasklet);
+		}
+
+		if (pending & (ATMEL_US_RXBRK | ATMEL_US_OVRE |
+				ATMEL_US_FRAME | ATMEL_US_PARE))
+			atmel_pdc_rxerr(port, pending);
+	}
+
 	/* Interrupt receive */
 	if (pending & ATMEL_US_RXRDY)
 		atmel_rx_chars(port);
@@ -387,10 +497,18 @@ atmel_handle_transmit(struct uart_port *port, unsigned int pending)
 {
 	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
 
-	/* Interrupt transmit */
-	if (pending & ATMEL_US_TXRDY) {
-		UART_PUT_IDR(port, ATMEL_US_TXRDY);
-		tasklet_schedule(&atmel_port->tasklet);
+	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);
+		}
 	}
 }
 
@@ -418,20 +536,67 @@ static irqreturn_t atmel_interrupt(int irq, void *dev_id)
 	struct uart_port *port = dev_id;
 	unsigned int status, pending, pass_counter = 0;
 
-	status = UART_GET_CSR(port);
-	pending = status & UART_GET_IMR(port);
-	while (pending) {
+	do {
+		status = UART_GET_CSR(port);
+		pending = status & UART_GET_IMR(port);
+		if (!pending)
+			break;
+
 		atmel_handle_receive(port, pending);
 		atmel_handle_status(port, pending, status);
 		atmel_handle_transmit(port, pending);
+	} while (pass_counter++ < ATMEL_ISR_PASS_LIMIT);
 
-		if (pass_counter++ > ATMEL_ISR_PASS_LIMIT)
-			break;
+	return IRQ_HANDLED;
+}
 
-		status = UART_GET_CSR(port);
-		pending = status & UART_GET_IMR(port);
+/*
+ * Called from tasklet with ENDTX and TXBUFE interrupts disabled.
+ */
+static void atmel_tx_dma(struct uart_port *port)
+{
+	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
+	struct circ_buf *xmit = &port->info->xmit;
+	struct atmel_dma_buffer *pdc = &atmel_port->pdc_tx;
+	int count;
+
+	xmit->tail += pdc->ofs;
+	if (xmit->tail >= SERIAL_XMIT_SIZE)
+		xmit->tail -= SERIAL_XMIT_SIZE;
+
+	port->icount.tx += pdc->ofs;
+	pdc->ofs = 0;
+
+	if (!uart_circ_empty(xmit)) {
+		/* more to transmit - setup next transfer */
+
+		/* disable PDC transmit */
+		UART_PUT_PTCR(port, ATMEL_PDC_TXTDIS);
+		dma_sync_single_for_device(port->dev,
+					   pdc->dma_addr,
+					   pdc->dma_size,
+					   DMA_TO_DEVICE);
+
+		if (xmit->tail < xmit->head)
+			count = xmit->head - xmit->tail;
+		else
+			count = SERIAL_XMIT_SIZE - xmit->tail;
+		pdc->ofs = count;
+
+		UART_PUT_TPR(port, pdc->dma_addr + xmit->tail);
+		UART_PUT_TCR(port, count);
+		/* re-enable PDC transmit and interrupts */
+		UART_PUT_PTCR(port, ATMEL_PDC_TXTEN);
+		UART_PUT_IER(port, ATMEL_US_ENDTX | ATMEL_US_TXBUFE);
+	} else {
+		/* nothing left to transmit - disable the transmitter */
+
+		/* disable PDC transmit */
+		UART_PUT_PTCR(port, ATMEL_PDC_TXTDIS);
 	}
-	return IRQ_HANDLED;
+
+	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+		uart_write_wakeup(port);
 }
 
 static void atmel_rx_from_ring(struct uart_port *port)
@@ -502,6 +667,76 @@ static void atmel_rx_from_ring(struct uart_port *port)
 	spin_lock(&port->lock);
 }
 
+static void atmel_rx_from_dma(struct uart_port *port)
+{
+	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
+	struct tty_struct *tty = port->info->tty;
+	struct atmel_dma_buffer *pdc;
+	int rx_idx = atmel_port->pdc_rx_idx;
+	unsigned int head;
+	unsigned int tail;
+	unsigned int count;
+
+	do {
+		/* Reset the UART timeout early so that we don't miss one */
+		UART_PUT_CR(port, ATMEL_US_STTTO);
+
+		pdc = &atmel_port->pdc_rx[rx_idx];
+		head = UART_GET_RPR(port) - pdc->dma_addr;
+		tail = pdc->ofs;
+
+		/* If the PDC has switched buffers, RPR won't contain
+		 * any address within the current buffer. Since head
+		 * is unsigned, we just need a one-way comparison to
+		 * find out.
+		 *
+		 * In this case, we just need to consume the entire
+		 * buffer and resubmit it for DMA. This will clear the
+		 * ENDRX bit as well, so that we can safely re-enable
+		 * all interrupts below.
+		 */
+		if (head >= pdc->dma_size)
+			head = pdc->dma_size;
+
+		if (likely(head != tail)) {
+			dma_sync_single_for_cpu(port->dev, pdc->dma_addr,
+					pdc->dma_size, DMA_FROM_DEVICE);
+
+			count = head - tail;
+			tty_insert_flip_string(tty, pdc->buf + pdc->ofs, count);
+
+			dma_sync_single_for_device(port->dev, pdc->dma_addr,
+					pdc->dma_size, DMA_FROM_DEVICE);
+
+			port->icount.rx += count;
+			pdc->ofs = head;
+		}
+
+		/*
+		 * If the current buffer is full, we need to check if
+		 * the next one contains any additional data.
+		 */
+		if (head >= pdc->dma_size) {
+			pdc->ofs = 0;
+			UART_PUT_RNPR(port, pdc->dma_addr);
+			UART_PUT_RNCR(port, pdc->dma_size);
+
+			rx_idx = !rx_idx;
+			atmel_port->pdc_rx_idx = rx_idx;
+		}
+	} while (head >= pdc->dma_size);
+
+	/*
+	 * Drop the lock here since it might end up calling
+	 * uart_start(), which takes the lock.
+	 */
+	spin_unlock(&port->lock);
+	tty_flip_buffer_push(tty);
+	spin_lock(&port->lock);
+
+	UART_PUT_IER(port, ATMEL_US_ENDRX | ATMEL_US_TIMEOUT);
+}
+
 /*
  * tasklet handling tty stuff outside the interrupt handler.
  */
@@ -515,7 +750,10 @@ static void atmel_tasklet_func(unsigned long data)
 	/* The interrupt handler does not take the lock */
 	spin_lock(&port->lock);
 
-	atmel_tx_chars(port);
+	if (atmel_use_dma_tx(port))
+		atmel_tx_dma(port);
+	else
+		atmel_tx_chars(port);
 
 	status = atmel_port->irq_status;
 	status_change = status ^ atmel_port->irq_status_prev;
@@ -537,7 +775,10 @@ static void atmel_tasklet_func(unsigned long data)
 		atmel_port->irq_status_prev = status;
 	}
 
-	atmel_rx_from_ring(port);
+	if (atmel_use_dma_rx(port))
+		atmel_rx_from_dma(port);
+	else
+		atmel_rx_from_ring(port);
 
 	spin_unlock(&port->lock);
 }
@@ -547,6 +788,7 @@ static void atmel_tasklet_func(unsigned long data)
  */
 static int atmel_startup(struct uart_port *port)
 {
+	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
 	int retval;
 
 	/*
@@ -567,6 +809,56 @@ static int atmel_startup(struct uart_port *port)
 	}
 
 	/*
+	 * Initialize DMA (if necessary)
+	 */
+	if (atmel_use_dma_rx(port)) {
+		int i;
+
+		for (i = 0; i < 2; i++) {
+			struct atmel_dma_buffer *pdc = &atmel_port->pdc_rx[i];
+
+			pdc->buf = kmalloc(PDC_BUFFER_SIZE, GFP_KERNEL);
+			if (pdc->buf == NULL) {
+				if (i != 0) {
+					dma_unmap_single(port->dev,
+						atmel_port->pdc_rx[0].dma_addr,
+						PDC_BUFFER_SIZE,
+						DMA_FROM_DEVICE);
+					kfree(atmel_port->pdc_rx[0].buf);
+				}
+				free_irq(port->irq, port);
+				return -ENOMEM;
+			}
+			pdc->dma_addr = dma_map_single(port->dev,
+						       pdc->buf,
+						       PDC_BUFFER_SIZE,
+						       DMA_FROM_DEVICE);
+			pdc->dma_size = PDC_BUFFER_SIZE;
+			pdc->ofs = 0;
+		}
+
+		atmel_port->pdc_rx_idx = 0;
+
+		UART_PUT_RPR(port, atmel_port->pdc_rx[0].dma_addr);
+		UART_PUT_RCR(port, PDC_BUFFER_SIZE);
+
+		UART_PUT_RNPR(port, atmel_port->pdc_rx[1].dma_addr);
+		UART_PUT_RNCR(port, PDC_BUFFER_SIZE);
+	}
+	if (atmel_use_dma_tx(port)) {
+		struct atmel_dma_buffer *pdc = &atmel_port->pdc_tx;
+		struct circ_buf *xmit = &port->info->xmit;
+
+		pdc->buf = xmit->buf;
+		pdc->dma_addr = dma_map_single(port->dev,
+					       pdc->buf,
+					       SERIAL_XMIT_SIZE,
+					       DMA_TO_DEVICE);
+		pdc->dma_size = SERIAL_XMIT_SIZE;
+		pdc->ofs = 0;
+	}
+
+	/*
 	 * If there is a specific "open" function (to register
 	 * control line interrupts)
 	 */
@@ -585,8 +877,18 @@ static int atmel_startup(struct uart_port *port)
 	/* enable xmit & rcvr */
 	UART_PUT_CR(port, ATMEL_US_TXEN | ATMEL_US_RXEN);
 
-	/* enable receive only */
-	UART_PUT_IER(port, ATMEL_US_RXRDY);
+	if (atmel_use_dma_rx(port)) {
+		/* set UART timeout */
+		UART_PUT_RTOR(port, PDC_RX_TIMEOUT);
+		UART_PUT_CR(port, ATMEL_US_STTTO);
+
+		UART_PUT_IER(port, ATMEL_US_ENDRX | ATMEL_US_TIMEOUT);
+		/* enable PDC controller */
+		UART_PUT_PTCR(port, ATMEL_PDC_RXTEN);
+	} else {
+		/* enable receive only */
+		UART_PUT_IER(port, ATMEL_US_RXRDY);
+	}
 
 	return 0;
 }
@@ -596,6 +898,38 @@ static int atmel_startup(struct uart_port *port)
  */
 static void atmel_shutdown(struct uart_port *port)
 {
+	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
+	/*
+	 * Ensure everything is stopped.
+	 */
+	atmel_stop_rx(port);
+	atmel_stop_tx(port);
+
+	/*
+	 * Shut-down the DMA.
+	 */
+	if (atmel_use_dma_rx(port)) {
+		int i;
+
+		for (i = 0; i < 2; i++) {
+			struct atmel_dma_buffer *pdc = &atmel_port->pdc_rx[i];
+
+			dma_unmap_single(port->dev,
+					 pdc->dma_addr,
+					 pdc->dma_size,
+					 DMA_FROM_DEVICE);
+			kfree(pdc->buf);
+		}
+	}
+	if (atmel_use_dma_tx(port)) {
+		struct atmel_dma_buffer *pdc = &atmel_port->pdc_tx;
+
+		dma_unmap_single(port->dev,
+				 pdc->dma_addr,
+				 pdc->dma_size,
+				 DMA_TO_DEVICE);
+	}
+
 	/*
 	 * Disable all interrupts, port and break condition.
 	 */
@@ -707,6 +1041,10 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios,
 	if (termios->c_iflag & (BRKINT | PARMRK))
 		port->read_status_mask |= ATMEL_US_RXBRK;
 
+	if (atmel_use_dma_rx(port))
+		/* need to enable error interrupts */
+		UART_PUT_IER(port, port->read_status_mask);
+
 	/*
 	 * Characters to ignore
 	 */
@@ -892,6 +1230,11 @@ static void __devinit atmel_init_port(struct atmel_uart_port *atmel_port,
 		clk_enable(atmel_port->clk);
 		port->uartclk = clk_get_rate(atmel_port->clk);
 	}
+
+	atmel_port->use_dma_rx = data->use_dma_rx;
+	atmel_port->use_dma_tx = data->use_dma_tx;
+	if (atmel_use_dma_tx(port))
+		port->fifosize = PDC_BUFFER_SIZE;
 }
 
 /*
@@ -1126,11 +1469,13 @@ static int __devinit atmel_serial_probe(struct platform_device *pdev)
 	port = &atmel_ports[pdev->id];
 	atmel_init_port(port, pdev);
 
-	ret = -ENOMEM;
-	data = kmalloc(ATMEL_SERIAL_RINGSIZE, GFP_KERNEL);
-	if (!data)
-		goto err_alloc_ring;
-	port->rx_ring.buf = data;
+	if (!atmel_use_dma_rx(&port->uart)) {
+		ret = -ENOMEM;
+		data = kmalloc(ATMEL_SERIAL_RINGSIZE, GFP_KERNEL);
+		if (!data)
+			goto err_alloc_ring;
+		port->rx_ring.buf = data;
+	}
 
 	ret = uart_add_one_port(&atmel_uart, &port->uart);
 	if (ret)
-- 
1.5.3.8

[PATCH -mm v4 8/9] atmel_serial: Use container_of instead of direct cast

[Haavard Skinnemoen]

As pointed out by David Brownell, we really ought to be using
container_of when converting from "struct uart_port *" to "struct
atmel_uart_port *".

Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
---
 drivers/serial/atmel_serial.c |   40 +++++++++++++++++++++++-----------------
 1 files changed, 23 insertions(+), 17 deletions(-)

diff --git a/drivers/serial/atmel_serial.c b/drivers/serial/atmel_serial.c
index e4f9449..2ff92b9 100644
--- a/drivers/serial/atmel_serial.c
+++ b/drivers/serial/atmel_serial.c
@@ -157,17 +157,23 @@ static struct atmel_uart_port atmel_ports[ATMEL_MAX_UART];
 static struct console atmel_console;
 #endif
 
+static inline struct atmel_uart_port *
+to_atmel_uart_port(struct uart_port *uart)
+{
+	return container_of(uart, struct atmel_uart_port, uart);
+}
+
 #ifdef CONFIG_SERIAL_ATMEL_PDC
 static bool atmel_use_dma_rx(struct uart_port *port)
 {
-	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
+	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
 
 	return atmel_port->use_dma_rx;
 }
 
 static bool atmel_use_dma_tx(struct uart_port *port)
 {
-	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
+	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
 
 	return atmel_port->use_dma_tx;
 }
@@ -330,7 +336,7 @@ static void
 atmel_buffer_rx_char(struct uart_port *port, unsigned int status,
 		     unsigned int ch)
 {
-	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
+	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
 	struct circ_buf *ring = &atmel_port->rx_ring;
 	struct atmel_uart_char *c;
 
@@ -374,7 +380,7 @@ static void atmel_pdc_rxerr(struct uart_port *port, unsigned int status)
  */
 static void atmel_rx_chars(struct uart_port *port)
 {
-	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
+	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
 	unsigned int status, ch;
 
 	status = UART_GET_CSR(port);
@@ -454,7 +460,7 @@ static void atmel_tx_chars(struct uart_port *port)
 static void
 atmel_handle_receive(struct uart_port *port, unsigned int pending)
 {
-	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
+	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
 
 	if (atmel_use_dma_rx(port)) {
 		/*
@@ -495,7 +501,7 @@ atmel_handle_receive(struct uart_port *port, unsigned int pending)
 static void
 atmel_handle_transmit(struct uart_port *port, unsigned int pending)
 {
-	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
+	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
 
 	if (atmel_use_dma_tx(port)) {
 		/* PDC transmit */
@@ -519,7 +525,7 @@ static void
 atmel_handle_status(struct uart_port *port, unsigned int pending,
 		    unsigned int status)
 {
-	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
+	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
 
 	if (pending & (ATMEL_US_RIIC | ATMEL_US_DSRIC | ATMEL_US_DCDIC
 				| ATMEL_US_CTSIC)) {
@@ -555,7 +561,7 @@ static irqreturn_t atmel_interrupt(int irq, void *dev_id)
  */
 static void atmel_tx_dma(struct uart_port *port)
 {
-	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
+	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
 	struct circ_buf *xmit = &port->info->xmit;
 	struct atmel_dma_buffer *pdc = &atmel_port->pdc_tx;
 	int count;
@@ -601,7 +607,7 @@ static void atmel_tx_dma(struct uart_port *port)
 
 static void atmel_rx_from_ring(struct uart_port *port)
 {
-	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
+	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
 	struct circ_buf *ring = &atmel_port->rx_ring;
 	unsigned int flg;
 	unsigned int status;
@@ -669,7 +675,7 @@ static void atmel_rx_from_ring(struct uart_port *port)
 
 static void atmel_rx_from_dma(struct uart_port *port)
 {
-	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
+	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
 	struct tty_struct *tty = port->info->tty;
 	struct atmel_dma_buffer *pdc;
 	int rx_idx = atmel_port->pdc_rx_idx;
@@ -743,7 +749,7 @@ static void atmel_rx_from_dma(struct uart_port *port)
 static void atmel_tasklet_func(unsigned long data)
 {
 	struct uart_port *port = (struct uart_port *)data;
-	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
+	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
 	unsigned int status;
 	unsigned int status_change;
 
@@ -788,7 +794,7 @@ static void atmel_tasklet_func(unsigned long data)
  */
 static int atmel_startup(struct uart_port *port)
 {
-	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
+	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
 	int retval;
 
 	/*
@@ -898,7 +904,7 @@ static int atmel_startup(struct uart_port *port)
  */
 static void atmel_shutdown(struct uart_port *port)
 {
-	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
+	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
 	/*
 	 * Ensure everything is stopped.
 	 */
@@ -955,7 +961,7 @@ static void atmel_shutdown(struct uart_port *port)
 static void atmel_serial_pm(struct uart_port *port, unsigned int state,
 			    unsigned int oldstate)
 {
-	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
+	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
 
 	switch (state) {
 	case 0:
@@ -1427,7 +1433,7 @@ static int atmel_serial_suspend(struct platform_device *pdev,
 				pm_message_t state)
 {
 	struct uart_port *port = platform_get_drvdata(pdev);
-	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
+	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
 
 	if (device_may_wakeup(&pdev->dev)
 	    && !at91_suspend_entering_slow_clock())
@@ -1443,7 +1449,7 @@ static int atmel_serial_suspend(struct platform_device *pdev,
 static int atmel_serial_resume(struct platform_device *pdev)
 {
 	struct uart_port *port = platform_get_drvdata(pdev);
-	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
+	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
 
 	if (atmel_port->suspended) {
 		uart_resume_port(&atmel_uart, port);
@@ -1502,7 +1508,7 @@ err_alloc_ring:
 static int __devexit atmel_serial_remove(struct platform_device *pdev)
 {
 	struct uart_port *port = platform_get_drvdata(pdev);
-	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
+	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
 	int ret = 0;
 
 	device_init_wakeup(&pdev->dev, 0);
-- 
1.5.3.8

[PATCH -mm v4 9/9] atmel_serial: Show tty name in /proc/interrupts

[Haavard Skinnemoen]

When possible, pass the tty name to request_irq() so that the user can
easily distinguish the different serial ports in /proc/interrupts.

Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
---
 drivers/serial/atmel_serial.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/drivers/serial/atmel_serial.c b/drivers/serial/atmel_serial.c
index 2ff92b9..63505cc 100644
--- a/drivers/serial/atmel_serial.c
+++ b/drivers/serial/atmel_serial.c
@@ -795,6 +795,7 @@ static void atmel_tasklet_func(unsigned long data)
 static int atmel_startup(struct uart_port *port)
 {
 	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
+	struct tty_struct *tty = port->info->tty;
 	int retval;
 
 	/*
@@ -808,7 +809,7 @@ static int atmel_startup(struct uart_port *port)
 	 * Allocate the IRQ
 	 */
 	retval = request_irq(port->irq, atmel_interrupt, IRQF_SHARED,
-			"atmel_serial", port);
+			tty ? tty->name : "atmel_serial", port);
 	if (retval) {
 		printk("atmel_serial: atmel_startup - Can't get irq\n");
 		return retval;
-- 
1.5.3.8

Re: [PATCH -mm v4 0/9] atmel_serial cleanups and improvements

[Marc Pignat]

Tested and working on at91rm9200 using 2.6.24-rc8, in one word... ack.

Regards

Marc

Re: [PATCH -mm v4 0/9] atmel_serial cleanups and improvements

[Haavard Skinnemoen]

On Thu, 24 Jan 2008 14:32:48 +0100
Marc Pignat <marc.pignat@hevs.ch> wrote:

> Tested and working on at91rm9200 using 2.6.24-rc8, in one word... ack.

Great! Thanks for testing!

Haavard

Re: [PATCH -mm v4 7/9] atmel_serial: Add DMA support

[Andrew Morton]

> On Thu, 24 Jan 2008 13:41:49 +0100 Haavard Skinnemoen <hskinnemoen@atmel.com> wrote:
> From: Chip Coldwell <coldwell@redhat.com>
> 
> This patch is based on the DMA-patch by Chip Coldwell for the
> AT91/AT32 serial USARTS, with some tweaks to make it apply neatly on
> top of the other patches in this series.
> 
> The RX and TX code has been moved to a tasklet and reworked a bit.
> Instead of depending on the ENDRX and TIMEOUT bits in CSR, we simply
> grab as much data as we can from the DMA buffers. I think this closes
> a race where the ENDRX bit is set after we read CSR but before we read
> RPR, although I haven't confirmed this.
> 
> Similarly, the two TX handlers (ENDTX and TXBUFE) have been combined
> into one. Since the current code only uses a single TX buffer, there's
> no point in handling those interrupts separately.
> 
> This also fixes a DMA sync bug in the original patch.
> 
> ...
>  
> +#define PDC_RX_BUF(port)	&(port)->pdc_rx[(port)->pdc_rx_idx]
> +#define PDC_RX_SWITCH(port)	(port)->pdc_rx_idx = !(port)->pdc_rx_idx

These macros refer to their arg more than one time and hance are dangerous.
Think of the effects of PDC_RX_BUF(foo++).

Generally, please don't use macros for anything which can be coded as a
regular C function.

> +/*
> + * Called from tasklet with ENDTX and TXBUFE interrupts disabled.
> + */
> +static void atmel_tx_dma(struct uart_port *port)
> +{
> +	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
> +	struct circ_buf *xmit = &port->info->xmit;
> +	struct atmel_dma_buffer *pdc = &atmel_port->pdc_tx;
> +	int count;
> +
> +	xmit->tail += pdc->ofs;
> +	if (xmit->tail >= SERIAL_XMIT_SIZE)
> +		xmit->tail -= SERIAL_XMIT_SIZE;

Maybe this should be a uart_circ_whatever() helper rather than open-coded.

> +	port->icount.tx += pdc->ofs;
> +	pdc->ofs = 0;
> +
> +	if (!uart_circ_empty(xmit)) {

ho-hum.  The generic uart buffer-handling code does ringbuffers the wrong
way.  Maybe it has to handle non-power-of-two buffer sizes.


> +		/* more to transmit - setup next transfer */
> +
> +		/* disable PDC transmit */
> +		UART_PUT_PTCR(port, ATMEL_PDC_TXTDIS);
> +		dma_sync_single_for_device(port->dev,
> +					   pdc->dma_addr,
> +					   pdc->dma_size,
> +					   DMA_TO_DEVICE);
> +
> +		if (xmit->tail < xmit->head)
> +			count = xmit->head - xmit->tail;
> +		else
> +			count = SERIAL_XMIT_SIZE - xmit->tail;

Doesn't uart_circ_chars_pending() do this?

All those uart_circ_*() macros reference their arg more than once and ... 
you know the deal.

> +		pdc->ofs = count;
> +
> +		UART_PUT_TPR(port, pdc->dma_addr + xmit->tail);
> +		UART_PUT_TCR(port, count);
> +		/* re-enable PDC transmit and interrupts */
> +		UART_PUT_PTCR(port, ATMEL_PDC_TXTEN);
> +		UART_PUT_IER(port, ATMEL_US_ENDTX | ATMEL_US_TXBUFE);
> +	} else {
> +		/* nothing left to transmit - disable the transmitter */
> +
> +		/* disable PDC transmit */
> +		UART_PUT_PTCR(port, ATMEL_PDC_TXTDIS);
>  	}
> -	return IRQ_HANDLED;
> +
> +	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
> +		uart_write_wakeup(port);
>  }
>  
>  static void atmel_rx_from_ring(struct uart_port *port)
> @@ -502,6 +667,76 @@ static void atmel_rx_from_ring(struct uart_port *port)
>  	spin_lock(&port->lock);
>  }
>  
> +static void atmel_rx_from_dma(struct uart_port *port)
> +{
> +	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
> +	struct tty_struct *tty = port->info->tty;
> +	struct atmel_dma_buffer *pdc;
> +	int rx_idx = atmel_port->pdc_rx_idx;
> +	unsigned int head;
> +	unsigned int tail;
> +	unsigned int count;
> +
> +	do {
> +		/* Reset the UART timeout early so that we don't miss one */
> +		UART_PUT_CR(port, ATMEL_US_STTTO);
> +
> +		pdc = &atmel_port->pdc_rx[rx_idx];
> +		head = UART_GET_RPR(port) - pdc->dma_addr;
> +		tail = pdc->ofs;
> +
> +		/* If the PDC has switched buffers, RPR won't contain
> +		 * any address within the current buffer. Since head
> +		 * is unsigned, we just need a one-way comparison to
> +		 * find out.
> +		 *
> +		 * In this case, we just need to consume the entire
> +		 * buffer and resubmit it for DMA. This will clear the
> +		 * ENDRX bit as well, so that we can safely re-enable
> +		 * all interrupts below.
> +		 */
> +		if (head >= pdc->dma_size)
> +			head = pdc->dma_size;

min()?

> +		if (likely(head != tail)) {
> +			dma_sync_single_for_cpu(port->dev, pdc->dma_addr,
> +					pdc->dma_size, DMA_FROM_DEVICE);
> +
> +			count = head - tail;

No wraparound issues here?

> +			tty_insert_flip_string(tty, pdc->buf + pdc->ofs, count);
> +
> +			dma_sync_single_for_device(port->dev, pdc->dma_addr,
> +					pdc->dma_size, DMA_FROM_DEVICE);
> +
> +			port->icount.rx += count;
> +			pdc->ofs = head;
> +		}
> +
> +		/*
> +		 * If the current buffer is full, we need to check if
> +		 * the next one contains any additional data.
> +		 */
> +		if (head >= pdc->dma_size) {
> +			pdc->ofs = 0;
> +			UART_PUT_RNPR(port, pdc->dma_addr);
> +			UART_PUT_RNCR(port, pdc->dma_size);
> +
> +			rx_idx = !rx_idx;
> +			atmel_port->pdc_rx_idx = rx_idx;
> +		}
> +	} while (head >= pdc->dma_size);
> +
> +	/*
> +	 * Drop the lock here since it might end up calling
> +	 * uart_start(), which takes the lock.
> +	 */
> +	spin_unlock(&port->lock);
> +	tty_flip_buffer_push(tty);
> +	spin_lock(&port->lock);
> +
> +	UART_PUT_IER(port, ATMEL_US_ENDRX | ATMEL_US_TIMEOUT);
> +}
> +

Re: [PATCH -mm v4 7/9] atmel_serial: Add DMA support

[Haavard Skinnemoen]

On Sat, 26 Jan 2008 22:02:00 -0800
Andrew Morton <akpm@linux-foundation.org> wrote:
> > On Thu, 24 Jan 2008 13:41:49 +0100 Haavard Skinnemoen <hskinnemoen@atmel.com> wrote:
> > +#define PDC_RX_BUF(port)	&(port)->pdc_rx[(port)->pdc_rx_idx]
> > +#define PDC_RX_SWITCH(port)	(port)->pdc_rx_idx = !(port)->pdc_rx_idx
> 
> These macros refer to their arg more than one time and hance are dangerous.
> Think of the effects of PDC_RX_BUF(foo++).

They're also unused...I'll remove them.

> Generally, please don't use macros for anything which can be coded as a
> regular C function.

Agree.

> > +/*
> > + * Called from tasklet with ENDTX and TXBUFE interrupts disabled.
> > + */
> > +static void atmel_tx_dma(struct uart_port *port)
> > +{
> > +	struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port;
> > +	struct circ_buf *xmit = &port->info->xmit;
> > +	struct atmel_dma_buffer *pdc = &atmel_port->pdc_tx;
> > +	int count;
> > +
> > +	xmit->tail += pdc->ofs;
> > +	if (xmit->tail >= SERIAL_XMIT_SIZE)
> > +		xmit->tail -= SERIAL_XMIT_SIZE;
> 
> Maybe this should be a uart_circ_whatever() helper rather than open-coded.

Hmm. uart_circ_get_multiple() or something?

Also, we should probably be using UART_XMIT_SIZE here, not
SERIAL_XMIT_SIZE. Why do we have two such definitions (which both
happen to be PAGE_SIZE)?

> > +	port->icount.tx += pdc->ofs;
> > +	pdc->ofs = 0;
> > +
> > +	if (!uart_circ_empty(xmit)) {
> 
> ho-hum.  The generic uart buffer-handling code does ringbuffers the wrong
> way.  Maybe it has to handle non-power-of-two buffer sizes.

Hmm...I don't understand. What does it do wrong?

> > +		/* more to transmit - setup next transfer */
> > +
> > +		/* disable PDC transmit */
> > +		UART_PUT_PTCR(port, ATMEL_PDC_TXTDIS);
> > +		dma_sync_single_for_device(port->dev,
> > +					   pdc->dma_addr,
> > +					   pdc->dma_size,
> > +					   DMA_TO_DEVICE);
> > +
> > +		if (xmit->tail < xmit->head)
> > +			count = xmit->head - xmit->tail;
> > +		else
> > +			count = SERIAL_XMIT_SIZE - xmit->tail;
> 
> Doesn't uart_circ_chars_pending() do this?

Hmm...no. I think we really want something CIRC_CNT_TO_END()-ish.

> All those uart_circ_*() macros reference their arg more than once and ... 
> you know the deal.

Yeah. Would you like a patch that inline-ifies <linux/circ.h>?

> > +		if (head >= pdc->dma_size)
> > +			head = pdc->dma_size;
> 
> min()?

Absolutely.

> > +		if (likely(head != tail)) {
> > +			dma_sync_single_for_cpu(port->dev, pdc->dma_addr,
> > +					pdc->dma_size, DMA_FROM_DEVICE);
> > +
> > +			count = head - tail;
> 
> No wraparound issues here?

No. "head" is the current offset that the DMA controller is reading
from, while "tail" is the offset we stopped at the last time around.
head will only wrap around when we recycle the DMA buffer, and when
that happens, we explicitly set tail to 0.

Haavard

Re: [PATCH -mm v4 7/9] atmel_serial: Add DMA support

[Andrew Morton]

On Mon, 28 Jan 2008 10:59:09 +0100 Haavard Skinnemoen <hskinnemoen@atmel.com> wrote:

> > ho-hum.  The generic uart buffer-handling code does ringbuffers the wrong
> > way.  Maybe it has to handle non-power-of-two buffer sizes.
> 
> Hmm...I don't understand. What does it do wrong?

An faq ;) If the buffer size is a power-of-two it's better to allow the
head and tail indices wrap through 0xffffffff and only mask them when
subscripting.  It ends up faster (usually) and you can use all of the
elements of the buffer (rather than all-1) and you get nice things like:

is_empty = (head == tail)
is_full = (tail - head == size)
nr_items_in_ring = (tail - head)


> > > +		/* more to transmit - setup next transfer */
> > > +
> > > +		/* disable PDC transmit */
> > > +		UART_PUT_PTCR(port, ATMEL_PDC_TXTDIS);
> > > +		dma_sync_single_for_device(port->dev,
> > > +					   pdc->dma_addr,
> > > +					   pdc->dma_size,
> > > +					   DMA_TO_DEVICE);
> > > +
> > > +		if (xmit->tail < xmit->head)
> > > +			count = xmit->head - xmit->tail;
> > > +		else
> > > +			count = SERIAL_XMIT_SIZE - xmit->tail;
> > 
> > Doesn't uart_circ_chars_pending() do this?
> 
> Hmm...no. I think we really want something CIRC_CNT_TO_END()-ish.
> 
> > All those uart_circ_*() macros reference their arg more than once and ... 
> > you know the deal.
> 
> Yeah. Would you like a patch that inline-ifies <linux/circ.h>?

uh, if you're feeling especially keen.  We have bigger problems than this.

Re: [PATCH -mm v4 7/9] atmel_serial: Add DMA support

[Haavard Skinnemoen]

On Mon, 28 Jan 2008 02:20:00 -0800
Andrew Morton <akpm@linux-foundation.org> wrote:

> On Mon, 28 Jan 2008 10:59:09 +0100 Haavard Skinnemoen <hskinnemoen@atmel.com> wrote:
> 
> > > ho-hum.  The generic uart buffer-handling code does ringbuffers the wrong
> > > way.  Maybe it has to handle non-power-of-two buffer sizes.
> > 
> > Hmm...I don't understand. What does it do wrong?
> 
> An faq ;) If the buffer size is a power-of-two it's better to allow the
> head and tail indices wrap through 0xffffffff and only mask them when
> subscripting.  It ends up faster (usually) and you can use all of the
> elements of the buffer (rather than all-1) and you get nice things like:
> 
> is_empty = (head == tail)
> is_full = (tail - head == size)
> nr_items_in_ring = (tail - head)

Ok, that makes sense. Thanks for explaining. Not sure if want to start
improving things right now, although I'm pretty sure the circ stuff
can't handle non-power-of-two buffer size currently so it should be
possible.

> > > All those uart_circ_*() macros reference their arg more than once and ... 
> > > you know the deal.
> > 
> > Yeah. Would you like a patch that inline-ifies <linux/circ.h>?
> 
> uh, if you're feeling especially keen.  We have bigger problems than this.

Well, if you put it like that; no, not really.

I'll post a fix for the other things you pointed out shortly.

Haavard

[PATCH -mm] atmel_serial dma: Misc fixes and cleanups

[Haavard Skinnemoen]

Fix some issues identified by Andrew Morton:
  * Kill unused PDC_RX_BUF() and PDC_RX_SWITCH() macros
  * Simplify TX circ buffer management a bit.
  * Don't open-code min()
  * Add comment explaining why "count = head - tail" will not cause
    wraparound problems.

Also, s/SERIAL_XMIT_SIZE/UART_XMIT_SIZE/ since the latter is what the
serial core circ macros use.

Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
---
Please fold into atmel_serial-add-dma-support.patch, or let me know if
you want a replacement for that patch.

 drivers/serial/atmel_serial.c |   27 +++++++++++++--------------
 1 files changed, 13 insertions(+), 14 deletions(-)

diff --git a/drivers/serial/atmel_serial.c b/drivers/serial/atmel_serial.c
index 63505cc..62654ab 100644
--- a/drivers/serial/atmel_serial.c
+++ b/drivers/serial/atmel_serial.c
@@ -114,7 +114,7 @@ static void (*atmel_close_hook)(struct uart_port *);
 struct atmel_dma_buffer {
 	unsigned char	*buf;
 	dma_addr_t	dma_addr;
-	size_t		dma_size;
+	unsigned int	dma_size;
 	unsigned int	ofs;
 };
 
@@ -150,9 +150,6 @@ struct atmel_uart_port {
 
 static struct atmel_uart_port atmel_ports[ATMEL_MAX_UART];
 
-#define PDC_RX_BUF(port)	&(port)->pdc_rx[(port)->pdc_rx_idx]
-#define PDC_RX_SWITCH(port)	(port)->pdc_rx_idx = !(port)->pdc_rx_idx
-
 #ifdef SUPPORT_SYSRQ
 static struct console atmel_console;
 #endif
@@ -567,8 +564,7 @@ static void atmel_tx_dma(struct uart_port *port)
 	int count;
 
 	xmit->tail += pdc->ofs;
-	if (xmit->tail >= SERIAL_XMIT_SIZE)
-		xmit->tail -= SERIAL_XMIT_SIZE;
+	xmit->tail &= UART_XMIT_SIZE - 1;
 
 	port->icount.tx += pdc->ofs;
 	pdc->ofs = 0;
@@ -583,10 +579,7 @@ static void atmel_tx_dma(struct uart_port *port)
 					   pdc->dma_size,
 					   DMA_TO_DEVICE);
 
-		if (xmit->tail < xmit->head)
-			count = xmit->head - xmit->tail;
-		else
-			count = SERIAL_XMIT_SIZE - xmit->tail;
+		count = CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE);
 		pdc->ofs = count;
 
 		UART_PUT_TPR(port, pdc->dma_addr + xmit->tail);
@@ -701,14 +694,20 @@ static void atmel_rx_from_dma(struct uart_port *port)
 		 * ENDRX bit as well, so that we can safely re-enable
 		 * all interrupts below.
 		 */
-		if (head >= pdc->dma_size)
-			head = pdc->dma_size;
+		head = min(head, pdc->dma_size);
 
 		if (likely(head != tail)) {
 			dma_sync_single_for_cpu(port->dev, pdc->dma_addr,
 					pdc->dma_size, DMA_FROM_DEVICE);
 
+			/*
+			 * head will only wrap around when we recycle
+			 * the DMA buffer, and when that happens, we
+			 * explicitly set tail to 0. So head will
+			 * always be greater than tail.
+			 */
 			count = head - tail;
+
 			tty_insert_flip_string(tty, pdc->buf + pdc->ofs, count);
 
 			dma_sync_single_for_device(port->dev, pdc->dma_addr,
@@ -859,9 +858,9 @@ static int atmel_startup(struct uart_port *port)
 		pdc->buf = xmit->buf;
 		pdc->dma_addr = dma_map_single(port->dev,
 					       pdc->buf,
-					       SERIAL_XMIT_SIZE,
+					       UART_XMIT_SIZE,
 					       DMA_TO_DEVICE);
-		pdc->dma_size = SERIAL_XMIT_SIZE;
+		pdc->dma_size = UART_XMIT_SIZE;
 		pdc->ofs = 0;
 	}
 
-- 
1.5.3.8