Commit 8412ba1d authored by Julien Masson's avatar Julien Masson Committed by Greg Kroah-Hartman
Browse files

tty: serial: meson_uart: Add support for kernel debugger 



The kgdb invokes the poll_put_char and poll_get_char when communicating
with the host. This patch implement the serial polling hooks for the
meson_uart to be used for KGDB debugging over serial line.

Signed-off-by: default avatarJulien Masson <jmasson@baylibre.com>
Link: https://lore.kernel.org/r/867e1klo48.fsf@julienm-fedora-R90NQGV9.i-did-not-set--mail-host-address--so-tickle-me


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 101aa46b

drivers/tty/serial/meson_uart.c

+65 −0
Original line number Diff line number Diff line
@@ -10,6 +10,7 @@ 
#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>
@@ -72,6 +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;
@@ -423,6 +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,
@@ -438,6 +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

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