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

This reverts commit 5021d709b31b8a14317998a33cbc78be0de9ab30.

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: 5021d709b31b ("tty: serial: Use fifo in 8250 console driver")
Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reported-by: Jon 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 2abb3de..3b12bfc 100644 (file)
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -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) {
@@ -3333,35 +3326,6 @@ static void serial8250_console_restore(struct uart_8250_port *up)
 }
 
 /*
- * 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();
@@ -3408,20 +3372,7 @@ 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);
+       uart_console_write(port, s, count, serial8250_console_putchar);
 
        /*
         *      Finally, wait for transmitter to become empty