From 6a7b9f002eca6788d346c16a6ff0c218b41f8d1d Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: Wed, 26 Jan 2022 14:33:58 +0100
Subject: [PATCH] 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>
---
drivers/tty/serial/8250/8250_port.c | 61 +++--------------------------
1 file changed, 6 insertions(+), 55 deletions(-)
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 2abb3de11a48b..3b12bfc1ed67b 100644
--- 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) {
@@ -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();
@@ -3408,20 +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
--
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