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Commit 38adbc54 authored by Michael Spang's avatar Michael Spang Committed by Greg Kroah-Hartman
Browse files

serial: samsung: Avoid waiting forever for TX ready 



The no_console_suspend option allows the console to write to the UART
during early resume, before the serial port itself is resumed. Such
writes hang indefinitely waiting for TX ready.

This adds a check to the console putchar function to drop characters
instead of hanging if the port hasn't been initialized. That way, we
can use no_console_suspend without risk of hanging.

Signed-off-by: default avatarMichael Spang <spang@chromium.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent d09a7308

drivers/tty/serial/samsung.c

+19 −3
Original line number Diff line number Diff line
@@ -1367,6 +1367,13 @@ s3c24xx_serial_console_txrdy(struct uart_port *port, unsigned int ufcon) 
	return (utrstat & S3C2410_UTRSTAT_TXE) ? 1 : 0;

}



static bool

s3c24xx_port_configured(unsigned int ucon)

{

	/* consider the serial port configured if the tx/rx mode set */

	return (ucon & 0xf) != 0;

}



#ifdef CONFIG_CONSOLE_POLL

/*

 * Console polling routines for writing and reading from the uart while
@@ -1389,6 +1396,11 @@ static void s3c24xx_serial_put_poll_char(struct uart_port *port, 
		unsigned char c)

{

	unsigned int ufcon = rd_regl(cons_uart, S3C2410_UFCON);

	unsigned int ucon = rd_regl(cons_uart, S3C2410_UCON);



	/* not possible to xmit on unconfigured port */

	if (!s3c24xx_port_configured(ucon))

		return;



	while (!s3c24xx_serial_console_txrdy(port, ufcon))

		cpu_relax();
@@ -1401,6 +1413,12 @@ static void 
s3c24xx_serial_console_putchar(struct uart_port *port, int ch)

{

	unsigned int ufcon = rd_regl(cons_uart, S3C2410_UFCON);

	unsigned int ucon = rd_regl(cons_uart, S3C2410_UCON);



	/* not possible to xmit on unconfigured port */

	if (!s3c24xx_port_configured(ucon))

		return;



	while (!s3c24xx_serial_console_txrdy(port, ufcon))

		barrier();

	wr_regb(cons_uart, S3C2410_UTXH, ch);
@@ -1433,9 +1451,7 @@ s3c24xx_serial_get_options(struct uart_port *port, int *baud, 
	    "registers: ulcon=%08x, ucon=%08x, ubdriv=%08x\n",

	    port, ulcon, ucon, ubrdiv);



	if ((ucon & 0xf) != 0) {

		/* consider the serial port configured if the tx/rx mode set */



	if (s3c24xx_port_configured(ucon)) {

		switch (ulcon & S3C2410_LCON_CSMASK) {

		case S3C2410_LCON_CS5:

			*bits = 5;