Merge tag 'tty-5.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty

Pull tty/serial driver updates from Greg KH:
 "Here are the big set of tty and serial driver updates for 5.6-rc1

  Included in here are:
   - dummy_con cleanups (touches lots of arch code)
   - sysrq logic cleanups (touches lots of serial drivers)
   - samsung driver fixes (wasn't really being built)
   - conmakeshash move to tty subdir out of scripts
   - lots of small tty/serial driver updates

  All of these have been in linux-next for a while with no reported
  issues"

* tag 'tty-5.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (140 commits)
  tty: n_hdlc: Use flexible-array member and struct_size() helper
  tty: baudrate: SPARC supports few more baud rates
  tty: baudrate: Synchronise baud_table[] and baud_bits[]
  tty: serial: meson_uart: Add support for kernel debugger
  serial: imx: fix a race condition in receive path
  serial: 8250_bcm2835aux: Document struct bcm2835aux_data
  serial: 8250_bcm2835aux: Use generic remapping code
  serial: 8250_bcm2835aux: Allocate uart_8250_port on stack
  serial: 8250_bcm2835aux: Suppress register_port error on -EPROBE_DEFER
  serial: 8250_bcm2835aux: Suppress clk_get error on -EPROBE_DEFER
  serial: 8250_bcm2835aux: Fix line mismatch on driver unbind
  serial_core: Remove unused member in uart_port
  vt: Correct comment documenting do_take_over_console()
  vt: Delete comment referencing non-existent unbind_con_driver()
  arch/xtensa/setup: Drop dummy_con initialization
  arch/x86/setup: Drop dummy_con initialization
  arch/unicore32/setup: Drop dummy_con initialization
  arch/sparc/setup: Drop dummy_con initialization
  arch/sh/setup: Drop dummy_con initialization
  arch/s390/setup: Drop dummy_con initialization
  ...

1 files changed, 66 insertions, 4 deletions

diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c
index 164b18372c02..d2c08b760f83 100644
--- a/drivers/tty/serial/meson_uart.c
+++ b/drivers/tty/serial/meson_uart.c
@@ -5,15 +5,12 @@
  * Copyright (C) 2014 Carlo Caione <carlo@caione.org>
  */
 
-#if defined(CONFIG_SERIAL_MESON_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
-#define SUPPORT_SYSRQ
-#endif
-
 #include <linux/clk.h>
 #include <linux/console.h>
 #include <linux/delay.h>
 #include <linux/init.h>
 #include <linux/io.h>
+#include <linux/iopoll.h>
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/of.h>
@@ -76,6 +73,8 @@
 #define AML_UART_PORT_OFFSET		6
 #define AML_UART_DEV_NAME		"ttyAML"
 
+#define AML_UART_POLL_USEC		5
+#define AML_UART_TIMEOUT_USEC		10000
 
 static struct uart_driver meson_uart_driver;
 
@@ -427,6 +426,64 @@ static void meson_uart_config_port(struct uart_port *port, int flags)
 	}
 }
 
+#ifdef CONFIG_CONSOLE_POLL
+/*
+ * Console polling routines for writing and reading from the uart while
+ * in an interrupt or debug context (i.e. kgdb).
+ */
+
+static int meson_uart_poll_get_char(struct uart_port *port)
+{
+	u32 c;
+	unsigned long flags;
+
+	spin_lock_irqsave(&port->lock, flags);
+
+	if (readl(port->membase + AML_UART_STATUS) & AML_UART_RX_EMPTY)
+		c = NO_POLL_CHAR;
+	else
+		c = readl(port->membase + AML_UART_RFIFO);
+
+	spin_unlock_irqrestore(&port->lock, flags);
+
+	return c;
+}
+
+static void meson_uart_poll_put_char(struct uart_port *port, unsigned char c)
+{
+	unsigned long flags;
+	u32 reg;
+	int ret;
+
+	spin_lock_irqsave(&port->lock, flags);
+
+	/* Wait until FIFO is empty or timeout */
+	ret = readl_poll_timeout_atomic(port->membase + AML_UART_STATUS, reg,
+					reg & AML_UART_TX_EMPTY,
+					AML_UART_POLL_USEC,
+					AML_UART_TIMEOUT_USEC);
+	if (ret == -ETIMEDOUT) {
+		dev_err(port->dev, "Timeout waiting for UART TX EMPTY\n");
+		goto out;
+	}
+
+	/* Write the character */
+	writel(c, port->membase + AML_UART_WFIFO);
+
+	/* Wait until FIFO is empty or timeout */
+	ret = readl_poll_timeout_atomic(port->membase + AML_UART_STATUS, reg,
+					reg & AML_UART_TX_EMPTY,
+					AML_UART_POLL_USEC,
+					AML_UART_TIMEOUT_USEC);
+	if (ret == -ETIMEDOUT)
+		dev_err(port->dev, "Timeout waiting for UART TX EMPTY\n");
+
+out:
+	spin_unlock_irqrestore(&port->lock, flags);
+}
+
+#endif /* CONFIG_CONSOLE_POLL */
+
 static const struct uart_ops meson_uart_ops = {
 	.set_mctrl      = meson_uart_set_mctrl,
 	.get_mctrl      = meson_uart_get_mctrl,
@@ -442,6 +499,10 @@ static const struct uart_ops meson_uart_ops = {
 	.request_port	= meson_uart_request_port,
 	.release_port	= meson_uart_release_port,
 	.verify_port	= meson_uart_verify_port,
+#ifdef CONFIG_CONSOLE_POLL
+	.poll_get_char	= meson_uart_poll_get_char,
+	.poll_put_char	= meson_uart_poll_put_char,
+#endif
 };
 
 #ifdef CONFIG_SERIAL_MESON_CONSOLE
@@ -703,6 +764,7 @@ static int meson_uart_probe(struct platform_device *pdev)
 	port->mapsize = resource_size(res_mem);
 	port->irq = res_irq->start;
 	port->flags = UPF_BOOT_AUTOCONF | UPF_LOW_LATENCY;
+	port->has_sysrq = IS_ENABLED(CONFIG_SERIAL_MESON_CONSOLE);
 	port->dev = &pdev->dev;
 	port->line = pdev->id;
 	port->type = PORT_MESON;