Commit 6a7b9f00 authored by Greg Kroah-Hartman's avatar Greg Kroah-Hartman
Browse files

Revert "tty: serial: Use fifo in 8250 console driver" 



This reverts commit 5021d709.

The patch is still a bit buggy, and this breaks some other hardware
types.  It needs to be resubmitted in a non-buggy way, and make sure the
other hardware types also continue to work properly.

Fixes: 5021d709 ("tty: serial: Use fifo in 8250 console driver")
Reported-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Reported-by: default avatarJon Hunter <jonathanh@nvidia.com>
Link: https://lore.kernel.org/r/Ye/1+Z8mEzbKbrqG@linutronix.de
Link: https://lore.kernel.org/r/a1ac6254-f79e-d131-fa2a-c7ad714c6d4a@nvidia.com


Cc: Wander Lairson Costa <wander@redhat.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent e783362e

drivers/tty/serial/8250/8250_port.c

+6 −55
Original line number Diff line number Diff line
@@ -2056,7 +2056,10 @@ static void serial8250_break_ctl(struct uart_port *port, int break_state) 
	serial8250_rpm_put(up);

}



static void wait_for_lsr(struct uart_8250_port *up, int bits)

/*

 *	Wait for transmitter & holding register to empty

 */

static void wait_for_xmitr(struct uart_8250_port *up, int bits)

{

	unsigned int status, tmout = 10000;
@@ -2073,16 +2076,6 @@ static void wait_for_lsr(struct uart_8250_port *up, int bits) 
		udelay(1);

		touch_nmi_watchdog();

	}

}



/*

 *	Wait for transmitter & holding register to empty

 */

static void wait_for_xmitr(struct uart_8250_port *up, int bits)

{

	unsigned int tmout;



	wait_for_lsr(up, bits);



	/* Wait up to 1s for flow control if necessary */

	if (up->port.flags & UPF_CONS_FLOW) {
@@ -3332,35 +3325,6 @@ static void serial8250_console_restore(struct uart_8250_port *up) 
	serial8250_out_MCR(up, UART_MCR_DTR | UART_MCR_RTS);

}



/*

 * Print a string to the serial port using the device FIFO

 *

 * It sends fifosize bytes and then waits for the fifo

 * to get empty.

 */

static void serial8250_console_fifo_write(struct uart_8250_port *up,

					  const char *s, unsigned int count)

{

	int i;

	const char *end = s + count;

	unsigned int fifosize = up->port.fifosize;

	bool cr_sent = false;



	while (s != end) {

		wait_for_lsr(up, UART_LSR_THRE);



		for (i = 0; i < fifosize && s != end; ++i) {

			if (*s == '\n' && !cr_sent) {

				serial_out(up, UART_TX, '\r');

				cr_sent = true;

			} else {

				serial_out(up, UART_TX, *s++);

				cr_sent = false;

			}

		}

	}

}



/*

 *	Print a string to the serial port trying not to disturb

 *	any possible real use of the port...
@@ -3376,7 +3340,7 @@ void serial8250_console_write(struct uart_8250_port *up, const char *s, 
	struct uart_8250_em485 *em485 = up->em485;

	struct uart_port *port = &up->port;

	unsigned long flags;

	unsigned int ier, use_fifo;

	unsigned int ier;

	int locked = 1;



	touch_nmi_watchdog();
@@ -3408,19 +3372,6 @@ void serial8250_console_write(struct uart_8250_port *up, const char *s, 
		mdelay(port->rs485.delay_rts_before_send);

	}



	use_fifo = (up->capabilities & UART_CAP_FIFO) &&

		port->fifosize > 1 &&

		(serial_port_in(port, UART_FCR) & UART_FCR_ENABLE_FIFO) &&

		/*

		 * After we put a data in the fifo, the controller will send

		 * it regardless of the CTS state. Therefore, only use fifo

		 * if we don't use control flow.

		 */

		!(up->port.flags & UPF_CONS_FLOW);



	if (likely(use_fifo))

		serial8250_console_fifo_write(up, s, count);

	else

	uart_console_write(port, s, count, serial8250_console_putchar);



	/*