Commit b86ac225 authored by Yixun Lan's avatar Yixun Lan Committed by Greg Kroah-Hartman
Browse files

serial: meson: add Magic SysRq support 



This dirver try to implement the Magic SysRq support[1] for
Amlogic Inc's meson platfo
>From the hardware perspective, the UART IP can't detect the 'BREAK' command
clearly via the status register. Instead, we rely on the combination of
'FRAME_ERR bit && ch == 0', and it works fine.

[1] Documentation/admin-guide/sysrq.rst

Signed-off-by: default avatarYixun Lan <dlan@gentoo.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 2bd6bf03

drivers/tty/serial/meson_uart.c

+16 −2
Original line number Diff line number Diff line
@@ -14,6 +14,10 @@ 
 *

 */



#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>
@@ -183,12 +187,12 @@ static void meson_receive_chars(struct uart_port *port) 
{

	struct tty_port *tport = &port->state->port;

	char flag;

	u32 status, ch, mode;

	u32 ostatus, status, ch, mode;



	do {

		flag = TTY_NORMAL;

		port->icount.rx++;

		status = readl(port->membase + AML_UART_STATUS);

		ostatus = status = readl(port->membase + AML_UART_STATUS);



		if (status & AML_UART_ERR) {

			if (status & AML_UART_TX_FIFO_WERR)
@@ -216,6 +220,16 @@ static void meson_receive_chars(struct uart_port *port) 
		ch = readl(port->membase + AML_UART_RFIFO);

		ch &= 0xff;



		if ((ostatus & AML_UART_FRAME_ERR) && (ch == 0)) {

			port->icount.brk++;

			flag = TTY_BREAK;

			if (uart_handle_break(port))

				continue;

		}



		if (uart_handle_sysrq_char(port, ch))

			continue;



		if ((status & port->ignore_status_mask) == 0)

			tty_insert_flip_char(tport, ch, flag);

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