Merge tag 'tty-4.21-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty

Pull tty/serial driver updates from Greg KH:
 "Here is the large TTY/Serial driver set of patches for 4.21-rc1.

  A number of small serial driver changes along with some good tty core
  fixes for long-reported issues with locking. There is also a new
  console font added to the tree, for high-res screens, so that should
  be helpful for many.

  The last patch in the series is a revert of an older one in the tree,
  it came late but it resolves a reported issue that linux-next was
  having for some people.

  Full details are in the shortlog, and all of these, with the exception
  of the revert, have been in linux-next for a while with no reported
  issues"

* tag 'tty-4.21-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (85 commits)
  Revert "serial: 8250: Default SERIAL_OF_PLATFORM to SERIAL_8250"
  serial: sccnxp: Allow to use non-standard baud rates
  serial: sccnxp: Adds a delay between sequential read/write cycles
  tty: serial: qcom_geni_serial: Fix UART hang
  tty: serial: qcom_geni_serial: Fix wrap around of TX buffer
  serial: max310x: Fix tx_empty() callback
  dt-bindings: serial: sh-sci: Document r8a774c0 bindings
  dt-bindings: serial: sh-sci: Document r8a774a1 bindings
  Fonts: New Terminus large console font
  dt-bindings: serial: lpuart: add imx8qxp compatible string
  serial: uartps: Fix interrupt mask issue to handle the RX interrupts properly
  serial: uartps: Fix error path when alloc failed
  serial: uartps: Check if the device is a console
  serial: uartps: Add the device_init_wakeup
  tty: serial: samsung: Increase maximum baudrate
  tty: serial: samsung: Properly set flags in autoCTS mode
  tty: Use of_node_name_{eq,prefix} for node name comparisons
  tty/serial: do not free trasnmit buffer page under port lock
  serial: 8250: Rate limit serial port rx interrupts during input overruns
  dt-bindings: serial: 8250: Add rate limit for serial port input overruns
  ...

Documentation/devicetree/bindings/dma/8250_mtk_dma.txt

@@ -0,0 +1,33 @@
+* Mediatek UART APDMA Controller
+
+Required properties:
+- compatible should contain:
+  * "mediatek,mt2712-uart-dma" for MT2712 compatible APDMA
+  * "mediatek,mt6577-uart-dma" for MT6577 and all of the above
+
+- reg: The base address of the APDMA register bank.
+
+- interrupts: A single interrupt specifier.
+
+- clocks : Must contain an entry for each entry in clock-names.
+  See ../clocks/clock-bindings.txt for details.
+- clock-names: The APDMA clock for register accesses
+
+Examples:
+
+	apdma: dma-controller@11000380 {
+		compatible = "mediatek,mt2712-uart-dma";
+		reg = <0 0x11000380 0 0x400>;
+		interrupts = <GIC_SPI 63 IRQ_TYPE_LEVEL_LOW>,
+			     <GIC_SPI 64 IRQ_TYPE_LEVEL_LOW>,
+			     <GIC_SPI 65 IRQ_TYPE_LEVEL_LOW>,
+			     <GIC_SPI 66 IRQ_TYPE_LEVEL_LOW>,
+			     <GIC_SPI 67 IRQ_TYPE_LEVEL_LOW>,
+			     <GIC_SPI 68 IRQ_TYPE_LEVEL_LOW>,
+			     <GIC_SPI 69 IRQ_TYPE_LEVEL_LOW>,
+			     <GIC_SPI 70 IRQ_TYPE_LEVEL_LOW>;
+		clocks = <&pericfg CLK_PERI_AP_DMA>;
+		clock-names = "apdma";
+		#dma-cells = <1>;
+	};
+

Documentation/devicetree/bindings/serial/8250.txt

@@ -51,6 +51,7 @@ Optional properties:
 - tx-threshold: Specify the TX FIFO low water indication for parts with
   programmable TX FIFO thresholds.
 - resets : phandle + reset specifier pairs
+- overrun-throttle-ms : how long to pause uart rx when input overrun is encountered.
 
 Note:
 * fsl,ns16550:

Documentation/devicetree/bindings/serial/fsl-lpuart.txt

@@ -8,6 +8,8 @@ Required properties:
     on LS1021A SoC with 32-bit big-endian register organization
   - "fsl,imx7ulp-lpuart" for lpuart compatible with the one integrated
     on i.MX7ULP SoC with 32-bit little-endian register organization
+  - "fsl,imx8qxp-lpuart" for lpuart compatible with the one integrated
+    on i.MX8QXP SoC with 32-bit little-endian register organization
 - reg : Address and length of the register set for the device
 - interrupts : Should contain uart interrupt
 - clocks : phandle + clock specifier pairs, one for each entry in clock-names

Documentation/devicetree/bindings/serial/lantiq_asc.txt

@@ -6,8 +6,23 @@ Required properties:
 - interrupts: the 3 (tx rx err) interrupt numbers. The interrupt specifier
   depends on the interrupt-parent interrupt controller.
 
+Optional properties:
+- clocks: Should contain frequency clock and gate clock
+- clock-names: Should be "freq" and "asc"
+
 Example:
 
+asc0: serial@16600000 {
+	compatible = "lantiq,asc";
+	reg = <0x16600000 0x100000>;
+	interrupt-parent = <&gic>;
+	interrupts = <GIC_SHARED 103 IRQ_TYPE_LEVEL_HIGH>,
+		<GIC_SHARED 105 IRQ_TYPE_LEVEL_HIGH>,
+		<GIC_SHARED 106 IRQ_TYPE_LEVEL_HIGH>;
+	clocks = <&cgu CLK_SSX4>, <&cgu GCLK_UART>;
+	clock-names = "freq", "asc";
+};
+
 asc1: serial@e100c00 {
 	compatible = "lantiq,asc";
 	reg = <0xE100C00 0x400>;

Documentation/devicetree/bindings/serial/renesas,sci-serial.txt

@@ -24,6 +24,10 @@ Required properties:
     - "renesas,hscif-r8a7745" for R8A7745 (RZ/G1E) HSCIF compatible UART.
     - "renesas,scif-r8a77470" for R8A77470 (RZ/G1C) SCIF compatible UART.
     - "renesas,hscif-r8a77470" for R8A77470 (RZ/G1C) HSCIF compatible UART.
+    - "renesas,scif-r8a774a1" for R8A774A1 (RZ/G2M) SCIF compatible UART.
+    - "renesas,hscif-r8a774a1" for R8A774A1 (RZ/G2M) HSCIF compatible UART.
+    - "renesas,scif-r8a774c0" for R8A774C0 (RZ/G2E) SCIF compatible UART.
+    - "renesas,hscif-r8a774c0" for R8A774C0 (RZ/G2E) HSCIF compatible UART.
     - "renesas,scif-r8a7778" for R8A7778 (R-Car M1) SCIF compatible UART.
     - "renesas,scif-r8a7779" for R8A7779 (R-Car H1) SCIF compatible UART.
     - "renesas,scif-r8a7790" for R8A7790 (R-Car H2) SCIF compatible UART.
@@ -61,13 +65,13 @@ Required properties:
     - "renesas,scifa-sh73a0" for SH73A0 (SH-Mobile AG5) SCIFA compatible UART.
     - "renesas,scifb-sh73a0" for SH73A0 (SH-Mobile AG5) SCIFB compatible UART.
     - "renesas,rcar-gen1-scif" for R-Car Gen1 SCIF compatible UART,
-    - "renesas,rcar-gen2-scif" for R-Car Gen2 SCIF compatible UART,
-    - "renesas,rcar-gen3-scif" for R-Car Gen3 SCIF compatible UART,
-    - "renesas,rcar-gen2-scifa" for R-Car Gen2 SCIFA compatible UART,
-    - "renesas,rcar-gen2-scifb" for R-Car Gen2 SCIFB compatible UART,
+    - "renesas,rcar-gen2-scif" for R-Car Gen2 and RZ/G1 SCIF compatible UART,
+    - "renesas,rcar-gen3-scif" for R-Car Gen3 and RZ/G2 SCIF compatible UART,
+    - "renesas,rcar-gen2-scifa" for R-Car Gen2 and RZ/G1 SCIFA compatible UART,
+    - "renesas,rcar-gen2-scifb" for R-Car Gen2 and RZ/G1 SCIFB compatible UART,
     - "renesas,rcar-gen1-hscif" for R-Car Gen1 HSCIF compatible UART,
-    - "renesas,rcar-gen2-hscif" for R-Car Gen2 HSCIF compatible UART,
-    - "renesas,rcar-gen3-hscif" for R-Car Gen3 HSCIF compatible UART,
+    - "renesas,rcar-gen2-hscif" for R-Car Gen2 and RZ/G1 HSCIF compatible UART,
+    - "renesas,rcar-gen3-hscif" for R-Car Gen3 and RZ/G2 HSCIF compatible UART,
     - "renesas,scif" for generic SCIF compatible UART.
     - "renesas,scifa" for generic SCIFA compatible UART.
     - "renesas,scifb" for generic SCIFB compatible UART.

drivers/char/Kconfig

@@ -66,6 +66,14 @@ config TTY_PRINTK
 
 	  If unsure, say N.
 
+config TTY_PRINTK_LEVEL
+	depends on TTY_PRINTK
+	int "ttyprintk log level (1-7)"
+	range 1 7
+	default "6"
+	help
+	  Printk log level to use for ttyprintk messages.
+
 config PRINTER
 	tristate "Parallel printer support"
 	depends on PARPORT

drivers/char/ttyprintk.c

@@ -37,6 +37,8 @@ static struct ttyprintk_port tpk_port;
  */
 #define TPK_STR_SIZE 508 /* should be bigger then max expected line length */
 #define TPK_MAX_ROOM 4096 /* we could assume 4K for instance */
+#define TPK_PREFIX KERN_SOH __stringify(CONFIG_TTY_PRINTK_LEVEL)
+
 static int tpk_curr;
 
 static char tpk_buffer[TPK_STR_SIZE + 4];
@@ -45,7 +47,7 @@ static void tpk_flush(void)
 {
 	if (tpk_curr > 0) {
 		tpk_buffer[tpk_curr] = '\0';
-		pr_info("[U] %s\n", tpk_buffer);
+		printk(TPK_PREFIX "[U] %s\n", tpk_buffer);
 		tpk_curr = 0;
 	}
 }

drivers/gnss/serial.c

@@ -65,7 +65,7 @@ static int gnss_serial_write_raw(struct gnss_device *gdev,
 
 	/* write is only buffered synchronously */
 	ret = serdev_device_write(serdev, buf, count, MAX_SCHEDULE_TIMEOUT);
-	if (ret < 0)
+	if (ret < 0 || ret < count)
 		return ret;
 
 	/* FIXME: determine if interrupted? */

drivers/gnss/sirf.c

@@ -85,7 +85,7 @@ static int sirf_write_raw(struct gnss_device *gdev, const unsigned char *buf,
 
 	/* write is only buffered synchronously */
 	ret = serdev_device_write(serdev, buf, count, MAX_SCHEDULE_TIMEOUT);
-	if (ret < 0)
+	if (ret < 0 || ret < count)
 		return ret;
 
 	/* FIXME: determine if interrupted? */

drivers/tty/hvc/hvc_opal.c

@@ -353,7 +353,7 @@ void __init hvc_opal_init_early(void)
 		if (!opal)
 			return;
 		for_each_child_of_node(opal, np) {
-			if (!strcmp(np->name, "serial")) {
+			if (of_node_name_eq(np, "serial")) {
 				stdout_node = np;
 				break;
 			}

drivers/tty/hvc/hvc_vio.c

@@ -371,20 +371,11 @@ device_initcall(hvc_vio_init); /* after drivers/tty/hvc/hvc_console.c */
 void __init hvc_vio_init_early(void)
 {
 	const __be32 *termno;
-	const char *name;
 	const struct hv_ops *ops;
 
 	/* find the boot console from /chosen/stdout */
-	if (!of_stdout)
-		return;
-	name = of_get_property(of_stdout, "name", NULL);
-	if (!name) {
-		printk(KERN_WARNING "stdout node missing 'name' property!\n");
-		return;
-	}
-
 	/* Check if it's a virtual terminal */
-	if (strncmp(name, "vty", 3) != 0)
+	if (!of_node_name_prefix(of_stdout, "vty"))
 		return;
 	termno = of_get_property(of_stdout, "reg", NULL);
 	if (termno == NULL)

drivers/tty/n_hdlc.c

@@ -612,7 +612,7 @@ static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
 		}
 			
 		/* no data */
-		if (file->f_flags & O_NONBLOCK) {
+		if (tty_io_nonblock(tty, file)) {
 			ret = -EAGAIN;
 			break;
 		}
@@ -679,7 +679,7 @@ static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
 		if (tbuf)
 			break;
 
-		if (file->f_flags & O_NONBLOCK) {
+		if (tty_io_nonblock(tty, file)) {
 			error = -EAGAIN;
 			break;
 		}

drivers/tty/n_r3964.c

@@ -1085,7 +1085,7 @@ static ssize_t r3964_read(struct tty_struct *tty, struct file *file,
 		pMsg = remove_msg(pInfo, pClient);
 		if (pMsg == NULL) {
 			/* no messages available. */
-			if (file->f_flags & O_NONBLOCK) {
+			if (tty_io_nonblock(tty, file)) {
 				ret = -EAGAIN;
 				goto unlock;
 			}

drivers/tty/n_tty.c

@@ -1702,7 +1702,7 @@ n_tty_receive_buf_common(struct tty_struct *tty, const unsigned char *cp,
 
 	down_read(&tty->termios_rwsem);
 
-	while (1) {
+	do {
 		/*
 		 * When PARMRK is set, each input char may take up to 3 chars
 		 * in the read buf; reduce the buffer space avail by 3x
@@ -1744,7 +1744,7 @@ n_tty_receive_buf_common(struct tty_struct *tty, const unsigned char *cp,
 			fp += n;
 		count -= n;
 		rcvd += n;
-	}
+	} while (!test_bit(TTY_LDISC_CHANGING, &tty->flags));
 
 	tty->receive_room = room;
 
@@ -2211,7 +2211,7 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
 					break;
 				if (!timeout)
 					break;
-				if (file->f_flags & O_NONBLOCK) {
+				if (tty_io_nonblock(tty, file)) {
 					retval = -EAGAIN;
 					break;
 				}
@@ -2365,7 +2365,7 @@ static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
 		}
 		if (!nr)
 			break;
-		if (file->f_flags & O_NONBLOCK) {
+		if (tty_io_nonblock(tty, file)) {
 			retval = -EAGAIN;
 			break;
 		}

drivers/tty/serdev/core.c

@@ -15,6 +15,7 @@
 #include <linux/of_device.h>
 #include <linux/pm_domain.h>
 #include <linux/pm_runtime.h>
+#include <linux/sched.h>
 #include <linux/serdev.h>
 #include <linux/slab.h>
 
@@ -216,6 +217,21 @@ void serdev_device_write_wakeup(struct serdev_device *serdev)
 }
 EXPORT_SYMBOL_GPL(serdev_device_write_wakeup);
 
+/**
+ * serdev_device_write_buf() - write data asynchronously
+ * @serdev:	serdev device
+ * @buf:	data to be written
+ * @count:	number of bytes to write
+ *
+ * Write data to the device asynchronously.
+ *
+ * Note that any accepted data has only been buffered by the controller; use
+ * serdev_device_wait_until_sent() to make sure the controller write buffer
+ * has actually been emptied.
+ *
+ * Return: The number of bytes written (less than count if not enough room in
+ * the write buffer), or a negative errno on errors.
+ */
 int serdev_device_write_buf(struct serdev_device *serdev,
 			    const unsigned char *buf, size_t count)
 {
@@ -228,17 +244,42 @@ int serdev_device_write_buf(struct serdev_device *serdev,
 }
 EXPORT_SYMBOL_GPL(serdev_device_write_buf);
 
+/**
+ * serdev_device_write() - write data synchronously
+ * @serdev:	serdev device
+ * @buf:	data to be written
+ * @count:	number of bytes to write
+ * @timeout:	timeout in jiffies, or 0 to wait indefinitely
+ *
+ * Write data to the device synchronously by repeatedly calling
+ * serdev_device_write() until the controller has accepted all data (unless
+ * interrupted by a timeout or a signal).
+ *
+ * Note that any accepted data has only been buffered by the controller; use
+ * serdev_device_wait_until_sent() to make sure the controller write buffer
+ * has actually been emptied.
+ *
+ * Note that this function depends on serdev_device_write_wakeup() being
+ * called in the serdev driver write_wakeup() callback.
+ *
+ * Return: The number of bytes written (less than count if interrupted),
+ * -ETIMEDOUT or -ERESTARTSYS if interrupted before any bytes were written, or
+ * a negative errno on errors.
+ */
 int serdev_device_write(struct serdev_device *serdev,
 			const unsigned char *buf, size_t count,
-			unsigned long timeout)
+			long timeout)
 {
 	struct serdev_controller *ctrl = serdev->ctrl;
+	int written = 0;
 	int ret;
 
-	if (!ctrl || !ctrl->ops->write_buf ||
-	    (timeout && !serdev->ops->write_wakeup))
+	if (!ctrl || !ctrl->ops->write_buf || !serdev->ops->write_wakeup)
 		return -EINVAL;
 
+	if (timeout == 0)
+		timeout = MAX_SCHEDULE_TIMEOUT;
+
 	mutex_lock(&serdev->write_lock);
 	do {
 		reinit_completion(&serdev->write_comp);
@@ -247,14 +288,29 @@ int serdev_device_write(struct serdev_device *serdev,
 		if (ret < 0)
 			break;
 
+		written += ret;
 		buf += ret;
 		count -= ret;
 
-	} while (count &&
-		 (timeout = wait_for_completion_timeout(&serdev->write_comp,
-							timeout)));
+		if (count == 0)
+			break;
+
+		timeout = wait_for_completion_interruptible_timeout(&serdev->write_comp,
+								    timeout);
+	} while (timeout > 0);
 	mutex_unlock(&serdev->write_lock);
-	return ret < 0 ? ret : (count ? -ETIMEDOUT : 0);
+
+	if (ret < 0)
+		return ret;
+
+	if (timeout <= 0 && written == 0) {
+		if (timeout == -ERESTARTSYS)
+			return -ERESTARTSYS;
+		else
+			return -ETIMEDOUT;
+	}
+
+	return written;
 }
 EXPORT_SYMBOL_GPL(serdev_device_write);
 

drivers/tty/serial/8250/8250_aspeed_vuart.c

@@ -5,6 +5,10 @@
  *    Copyright (C) 2016 Jeremy Kerr <jk@ozlabs.org>, IBM Corp.
  *    Copyright (C) 2006 Arnd Bergmann <arnd@arndb.de>, IBM Corp.
  */
+#if defined(CONFIG_SERIAL_8250_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
+#define SUPPORT_SYSRQ
+#endif
+
 #include <linux/device.h>
 #include <linux/module.h>
 #include <linux/of_address.h>
@@ -293,7 +297,7 @@ static int aspeed_vuart_handle_irq(struct uart_port *port)
 	if (lsr & UART_LSR_THRE)
 		serial8250_tx_chars(up);
 
-	spin_unlock_irqrestore(&port->lock, flags);
+	uart_unlock_and_check_sysrq(port, flags);
 
 	return 1;
 }

drivers/tty/serial/8250/8250_core.c

@@ -942,6 +942,21 @@ static struct uart_8250_port *serial8250_find_match_or_unused(struct uart_port *
 	return NULL;
 }
 
+static void serial_8250_overrun_backoff_work(struct work_struct *work)
+{
+	struct uart_8250_port *up =
+	    container_of(to_delayed_work(work), struct uart_8250_port,
+			 overrun_backoff);
+	struct uart_port *port = &up->port;
+	unsigned long flags;
+
+	spin_lock_irqsave(&port->lock, flags);
+	up->ier |= UART_IER_RLSI | UART_IER_RDI;
+	up->port.read_status_mask |= UART_LSR_DR;
+	serial_out(up, UART_IER, up->ier);
+	spin_unlock_irqrestore(&port->lock, flags);
+}
+
 /**
  *	serial8250_register_8250_port - register a serial port
  *	@up: serial port template
@@ -1056,6 +1071,16 @@ int serial8250_register_8250_port(struct uart_8250_port *up)
 			ret = 0;
 		}
 	}
+
+	/* Initialise interrupt backoff work if required */
+	if (up->overrun_backoff_time_ms > 0) {
+		uart->overrun_backoff_time_ms = up->overrun_backoff_time_ms;
+		INIT_DELAYED_WORK(&uart->overrun_backoff,
+				  serial_8250_overrun_backoff_work);
+	} else {
+		uart->overrun_backoff_time_ms = 0;
+	}
+
 	mutex_unlock(&serial_mutex);
 
 	return ret;

drivers/tty/serial/8250/8250_fsl.c

@@ -1,4 +1,8 @@
 // SPDX-License-Identifier: GPL-2.0
+#if defined(CONFIG_SERIAL_8250_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
+#define SUPPORT_SYSRQ
+#endif
+
 #include <linux/serial_reg.h>
 #include <linux/serial_8250.h>
 
@@ -45,8 +49,29 @@ int fsl8250_handle_irq(struct uart_port *port)
 
 	lsr = orig_lsr = up->port.serial_in(&up->port, UART_LSR);
 
-	if (lsr & (UART_LSR_DR | UART_LSR_BI))
+	/* Process incoming characters first */
+	if ((lsr & (UART_LSR_DR | UART_LSR_BI)) &&
+	    (up->ier & (UART_IER_RLSI | UART_IER_RDI))) {
 		lsr = serial8250_rx_chars(up, lsr);
+	}
+
+	/* Stop processing interrupts on input overrun */
+	if ((orig_lsr & UART_LSR_OE) && (up->overrun_backoff_time_ms > 0)) {
+		unsigned long delay;
+
+		up->ier = port->serial_in(port, UART_IER);
+		if (up->ier & (UART_IER_RLSI | UART_IER_RDI)) {
+			port->ops->stop_rx(port);
+		} else {
+			/* Keep restarting the timer until
+			 * the input overrun subsides.
+			 */
+			cancel_delayed_work(&up->overrun_backoff);
+		}
+
+		delay = msecs_to_jiffies(up->overrun_backoff_time_ms);
+		schedule_delayed_work(&up->overrun_backoff, delay);
+	}
 
 	serial8250_modem_status(up);
 
@@ -54,7 +79,7 @@ int fsl8250_handle_irq(struct uart_port *port)
 		serial8250_tx_chars(up);
 
 	up->lsr_saved_flags = orig_lsr;
-	spin_unlock_irqrestore(&up->port.lock, flags);
+	uart_unlock_and_check_sysrq(&up->port, flags);
 	return 1;
 }
 EXPORT_SYMBOL_GPL(fsl8250_handle_irq);

drivers/tty/serial/8250/8250_mtk.c

@@ -14,6 +14,10 @@
 #include <linux/pm_runtime.h>
 #include <linux/serial_8250.h>
 #include <linux/serial_reg.h>
+#include <linux/console.h>
+#include <linux/dma-mapping.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
 
 #include "8250.h"
 
@@ -22,12 +26,172 @@
 #define UART_MTK_SAMPLE_POINT	0x0b	/* Sample point register */
 #define MTK_UART_RATE_FIX	0x0d	/* UART Rate Fix Register */
 
+#define MTK_UART_DMA_EN		0x13	/* DMA Enable register */
+#define MTK_UART_DMA_EN_TX	0x2
+#define MTK_UART_DMA_EN_RX	0x5
+
+#define MTK_UART_TX_SIZE	UART_XMIT_SIZE
+#define MTK_UART_RX_SIZE	0x8000
+#define MTK_UART_TX_TRIGGER	1
+#define MTK_UART_RX_TRIGGER	MTK_UART_RX_SIZE
+
+#ifdef CONFIG_SERIAL_8250_DMA
+enum dma_rx_status {
+	DMA_RX_START = 0,
+	DMA_RX_RUNNING = 1,
+	DMA_RX_SHUTDOWN = 2,
+};
+#endif
+
 struct mtk8250_data {
 	int			line;
+	unsigned int		rx_pos;
 	struct clk		*uart_clk;
 	struct clk		*bus_clk;
+	struct uart_8250_dma	*dma;
+#ifdef CONFIG_SERIAL_8250_DMA
+	enum dma_rx_status	rx_status;
+#endif
 };
 
+#ifdef CONFIG_SERIAL_8250_DMA
+static void mtk8250_rx_dma(struct uart_8250_port *up);
+
+static void mtk8250_dma_rx_complete(void *param)
+{
+	struct uart_8250_port *up = param;
+	struct uart_8250_dma *dma = up->dma;
+	struct mtk8250_data *data = up->port.private_data;
+	struct tty_port *tty_port = &up->port.state->port;
+	struct dma_tx_state state;
+	unsigned char *ptr;
+	int copied;
+
+	dma_sync_single_for_cpu(dma->rxchan->device->dev, dma->rx_addr,
+				dma->rx_size, DMA_FROM_DEVICE);
+
+	dmaengine_tx_status(dma->rxchan, dma->rx_cookie, &state);
+
+	if (data->rx_status == DMA_RX_SHUTDOWN)
+		return;
+
+	if ((data->rx_pos + state.residue) <= dma->rx_size) {
+		ptr = (unsigned char *)(data->rx_pos + dma->rx_buf);
+		copied = tty_insert_flip_string(tty_port, ptr, state.residue);
+	} else {
+		ptr = (unsigned char *)(data->rx_pos + dma->rx_buf);
+		copied = tty_insert_flip_string(tty_port, ptr,
+						dma->rx_size - data->rx_pos);
+		ptr = (unsigned char *)(dma->rx_buf);
+		copied += tty_insert_flip_string(tty_port, ptr,
+				data->rx_pos + state.residue - dma->rx_size);
+	}
+	up->port.icount.rx += copied;
+
+	tty_flip_buffer_push(tty_port);
+
+	mtk8250_rx_dma(up);
+}
+
+static void mtk8250_rx_dma(struct uart_8250_port *up)
+{
+	struct uart_8250_dma *dma = up->dma;
+	struct mtk8250_data *data = up->port.private_data;
+	struct dma_async_tx_descriptor	*desc;
+	struct dma_tx_state	 state;
+
+	desc = dmaengine_prep_slave_single(dma->rxchan, dma->rx_addr,
+					   dma->rx_size, DMA_DEV_TO_MEM,
+					   DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
+	if (!desc) {
+		pr_err("failed to prepare rx slave single\n");
+		return;
+	}
+
+	desc->callback = mtk8250_dma_rx_complete;
+	desc->callback_param = up;
+
+	dma->rx_cookie = dmaengine_submit(desc);
+
+	dmaengine_tx_status(dma->rxchan, dma->rx_cookie, &state);
+	data->rx_pos = state.residue;
+
+	dma_sync_single_for_device(dma->rxchan->device->dev, dma->rx_addr,
+				   dma->rx_size, DMA_FROM_DEVICE);
+
+	dma_async_issue_pending(dma->rxchan);
+}
+
+static void mtk8250_dma_enable(struct uart_8250_port *up)
+{
+	struct uart_8250_dma *dma = up->dma;
+	struct mtk8250_data *data = up->port.private_data;
+	int lcr = serial_in(up, UART_LCR);
+
+	if (data->rx_status != DMA_RX_START)
+		return;
+
+	dma->rxconf.direction		= DMA_DEV_TO_MEM;
+	dma->rxconf.src_addr_width	= dma->rx_size / 1024;
+	dma->rxconf.src_addr		= dma->rx_addr;
+
+	dma->txconf.direction		= DMA_MEM_TO_DEV;
+	dma->txconf.dst_addr_width	= MTK_UART_TX_SIZE / 1024;
+	dma->txconf.dst_addr		= dma->tx_addr;
+
+	serial_out(up, UART_FCR, UART_FCR_ENABLE_FIFO | UART_FCR_CLEAR_RCVR |
+		UART_FCR_CLEAR_XMIT);
+	serial_out(up, MTK_UART_DMA_EN,
+		   MTK_UART_DMA_EN_RX | MTK_UART_DMA_EN_TX);
+
+	serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
+	serial_out(up, UART_EFR, UART_EFR_ECB);
+	serial_out(up, UART_LCR, lcr);
+
+	if (dmaengine_slave_config(dma->rxchan, &dma->rxconf) != 0)
+		pr_err("failed to configure rx dma channel\n");
+	if (dmaengine_slave_config(dma->txchan, &dma->txconf) != 0)
+		pr_err("failed to configure tx dma channel\n");
+
+	data->rx_status = DMA_RX_RUNNING;
+	data->rx_pos = 0;
+	mtk8250_rx_dma(up);
+}
+#endif
+
+static int mtk8250_startup(struct uart_port *port)
+{
+#ifdef CONFIG_SERIAL_8250_DMA
+	struct uart_8250_port *up = up_to_u8250p(port);
+	struct mtk8250_data *data = port->private_data;
+
+	/* disable DMA for console */
+	if (uart_console(port))
+		up->dma = NULL;
+
+	if (up->dma) {
+		data->rx_status = DMA_RX_START;
+		uart_circ_clear(&port->state->xmit);
+	}
+#endif
+	memset(&port->icount, 0, sizeof(port->icount));
+
+	return serial8250_do_startup(port);
+}
+
+static void mtk8250_shutdown(struct uart_port *port)
+{
+#ifdef CONFIG_SERIAL_8250_DMA
+	struct uart_8250_port *up = up_to_u8250p(port);
+	struct mtk8250_data *data = port->private_data;
+
+	if (up->dma)
+		data->rx_status = DMA_RX_SHUTDOWN;
+#endif
+
+	return serial8250_do_shutdown(port);
+}
+
 static void
 mtk8250_set_termios(struct uart_port *port, struct ktermios *termios,
 			struct ktermios *old)
@@ -36,6 +200,17 @@ mtk8250_set_termios(struct uart_port *port, struct ktermios *termios,
 	unsigned long flags;
 	unsigned int baud, quot;
 
+#ifdef CONFIG_SERIAL_8250_DMA
+	if (up->dma) {
+		if (uart_console(port)) {
+			devm_kfree(up->port.dev, up->dma);
+			up->dma = NULL;
+		} else {
+			mtk8250_dma_enable(up);
+		}
+	}
+#endif
+
 	serial8250_do_set_termios(port, termios, old);
 
 	/*
@@ -143,9 +318,20 @@ mtk8250_do_pm(struct uart_port *port, unsigned int state, unsigned int old)
 		pm_runtime_put_sync_suspend(port->dev);
 }
 
+#ifdef CONFIG_SERIAL_8250_DMA
+static bool mtk8250_dma_filter(struct dma_chan *chan, void *param)
+{
+	return false;
+}
+#endif
+
 static int mtk8250_probe_of(struct platform_device *pdev, struct uart_port *p,
 			   struct mtk8250_data *data)
 {
+#ifdef CONFIG_SERIAL_8250_DMA
+	int dmacnt;
+#endif
+
 	data->uart_clk = devm_clk_get(&pdev->dev, "baud");
 	if (IS_ERR(data->uart_clk)) {
 		/*
@@ -162,7 +348,23 @@ static int mtk8250_probe_of(struct platform_device *pdev, struct uart_port *p,
 	}
 
 	data->bus_clk = devm_clk_get(&pdev->dev, "bus");
-	return PTR_ERR_OR_ZERO(data->bus_clk);
+	if (IS_ERR(data->bus_clk))
+		return PTR_ERR(data->bus_clk);
+
+	data->dma = NULL;
+#ifdef CONFIG_SERIAL_8250_DMA
+	dmacnt = of_property_count_strings(pdev->dev.of_node, "dma-names");
+	if (dmacnt == 2) {
+		data->dma = devm_kzalloc(&pdev->dev, sizeof(*data->dma),
+					 GFP_KERNEL);
+		data->dma->fn = mtk8250_dma_filter;
+		data->dma->rx_size = MTK_UART_RX_SIZE;
+		data->dma->rxconf.src_maxburst = MTK_UART_RX_TRIGGER;
+		data->dma->txconf.dst_maxburst = MTK_UART_TX_TRIGGER;
+	}
+#endif
+
+	return 0;
 }
 
 static int mtk8250_probe(struct platform_device *pdev)
@@ -204,8 +406,14 @@ static int mtk8250_probe(struct platform_device *pdev)
 	uart.port.iotype = UPIO_MEM32;
 	uart.port.regshift = 2;
 	uart.port.private_data = data;
+	uart.port.shutdown = mtk8250_shutdown;
+	uart.port.startup = mtk8250_startup;
 	uart.port.set_termios = mtk8250_set_termios;
 	uart.port.uartclk = clk_get_rate(data->uart_clk);
+#ifdef CONFIG_SERIAL_8250_DMA
+	if (data->dma)
+		uart.dma = data->dma;
+#endif
 
 	/* Disable Rate Fix function */
 	writel(0x0, uart.port.membase +

drivers/tty/serial/8250/8250_of.c

@@ -240,6 +240,11 @@ static int of_platform_serial_probe(struct platform_device *ofdev)
 	if (of_property_read_bool(ofdev->dev.of_node, "auto-flow-control"))
 		port8250.capabilities |= UART_CAP_AFE;
 
+	if (of_property_read_u32(ofdev->dev.of_node,
+			"overrun-throttle-ms",
+			&port8250.overrun_backoff_time_ms) != 0)
+		port8250.overrun_backoff_time_ms = 0;
+
 	ret = serial8250_register_8250_port(&port8250);
 	if (ret < 0)
 		goto err_dispose;