Merge: Backport two upstream reverts of serial port patches found to cause timeouts.

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-10/-/merge_requests/878

Backport two upstream reverts of serial port patches found to cause timeouts.

JIRA: https://issues.redhat.com/browse/RHEL-56242

Resolves: RHEL-56242

Signed-off-by: John W. Linville <linville@redhat.com>

Approved-by: Tony Camuso <tcamuso@redhat.com>
Approved-by: Lenny Szubowicz <lszubowi@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: CKI GitLab Kmaint Pipeline Bot <26919896-cki-kmaint-pipeline-bot@users.noreply.gitlab.com>

Author: CKI KWF Bot

drivers/tty/serial/8250/8250_core.c

@@ -388,45 +388,13 @@ void __init serial8250_register_ports(struct uart_driver *drv, struct device *de
 
 #ifdef CONFIG_SERIAL_8250_CONSOLE
 
-#ifdef CONFIG_SERIAL_8250_LEGACY_CONSOLE
 static void univ8250_console_write(struct console *co, const char *s,
 				   unsigned int count)
 {
 	struct uart_8250_port *up = &serial8250_ports[co->index];
 
 	serial8250_console_write(up, s, count);
 }
-#else
-static void univ8250_console_write_atomic(struct console *co,
-					  struct nbcon_write_context *wctxt)
-{
-	struct uart_8250_port *up = &serial8250_ports[co->index];
-
-	serial8250_console_write_atomic(up, wctxt);
-}
-
-static void univ8250_console_write_thread(struct console *co,
-					  struct nbcon_write_context *wctxt)
-{
-	struct uart_8250_port *up = &serial8250_ports[co->index];
-
-	serial8250_console_write_thread(up, wctxt);
-}
-
-static void univ8250_console_device_lock(struct console *con, unsigned long *flags)
-{
-	struct uart_port *up = &serial8250_ports[con->index].port;
-
-	__uart_port_lock_irqsave(up, flags);
-}
-
-static void univ8250_console_device_unlock(struct console *con, unsigned long flags)
-{
-	struct uart_port *up = &serial8250_ports[con->index].port;
-
-	__uart_port_unlock_irqrestore(up, flags);
-}
-#endif /* CONFIG_SERIAL_8250_LEGACY_CONSOLE */
 
 static int univ8250_console_setup(struct console *co, char *options)
 {
@@ -526,20 +494,12 @@ static int univ8250_console_match(struct console *co, char *name, int idx,
 
 static struct console univ8250_console = {
 	.name		= "ttyS",
-#ifdef CONFIG_SERIAL_8250_LEGACY_CONSOLE
 	.write		= univ8250_console_write,
-	.flags		= CON_PRINTBUFFER | CON_ANYTIME,
-#else
-	.write_atomic	= univ8250_console_write_atomic,
-	.write_thread	= univ8250_console_write_thread,
-	.device_lock	= univ8250_console_device_lock,
-	.device_unlock	= univ8250_console_device_unlock,
-	.flags		= CON_PRINTBUFFER | CON_ANYTIME | CON_NBCON,
-#endif
 	.device		= uart_console_device,
 	.setup		= univ8250_console_setup,
 	.exit		= univ8250_console_exit,
 	.match		= univ8250_console_match,
+	.flags		= CON_PRINTBUFFER | CON_ANYTIME,
 	.index		= -1,
 	.data		= &serial8250_reg,
 };

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

@@ -546,13 +546,6 @@ static int serial8250_em485_init(struct uart_8250_port *p)
 	if (!p->em485)
 		return -ENOMEM;
 
-#ifndef CONFIG_SERIAL_8250_LEGACY_CONSOLE
-	if (uart_console(&p->port)) {
-		dev_warn(p->port.dev, "no atomic printing for rs485 consoles\n");
-		p->port.cons->write_atomic = NULL;
-	}
-#endif
-
 	hrtimer_init(&p->em485->stop_tx_timer, CLOCK_MONOTONIC,
 		     HRTIMER_MODE_REL);
 	hrtimer_init(&p->em485->start_tx_timer, CLOCK_MONOTONIC,
@@ -698,26 +691,14 @@ static void serial8250_set_sleep(struct uart_8250_port *p, int sleep)
 	serial8250_rpm_put(p);
 }
 
-/*
- * Only to be used by write_atomic() and the legacy write(), which do not
- * require port lock.
- */
-static void __serial8250_clear_IER(struct uart_8250_port *up)
+static void serial8250_clear_IER(struct uart_8250_port *up)
 {
 	if (up->capabilities & UART_CAP_UUE)
 		serial_out(up, UART_IER, UART_IER_UUE);
 	else
 		serial_out(up, UART_IER, 0);
 }
 
-static inline void serial8250_clear_IER(struct uart_8250_port *up)
-{
-	/* Port locked to synchronize UART_IER access against the console. */
-	lockdep_assert_held_once(&up->port.lock);
-
-	__serial8250_clear_IER(up);
-}
-
 #ifdef CONFIG_SERIAL_8250_RSA
 /*
  * Attempts to turn on the RSA FIFO.  Returns zero on failure.
@@ -3288,11 +3269,6 @@ static void serial8250_console_putchar(struct uart_port *port, unsigned char ch)
 
 	wait_for_xmitr(up, UART_LSR_THRE);
 	serial_port_out(port, UART_TX, ch);
-
-	if (ch == '\n')
-		up->console_newline_needed = false;
-	else
-		up->console_newline_needed = true;
 }
 
 /*
@@ -3321,7 +3297,6 @@ static void serial8250_console_restore(struct uart_8250_port *up)
 	serial8250_out_MCR(up, up->mcr | UART_MCR_DTR | UART_MCR_RTS);
 }
 
-#ifdef CONFIG_SERIAL_8250_LEGACY_CONSOLE
 /*
  * Print a string to the serial port using the device FIFO
  *
@@ -3380,7 +3355,7 @@ void serial8250_console_write(struct uart_8250_port *up, const char *s,
 	 *	First save the IER then disable the interrupts
 	 */
 	ier = serial_port_in(port, UART_IER);
-	__serial8250_clear_IER(up);
+	serial8250_clear_IER(up);
 
 	/* check scratch reg to see if port powered off during system sleep */
 	if (up->canary && (up->canary != serial_port_in(port, UART_SCR))) {
@@ -3446,131 +3421,6 @@ void serial8250_console_write(struct uart_8250_port *up, const char *s,
 	if (locked)
 		uart_port_unlock_irqrestore(port, flags);
 }
-#else
-void serial8250_console_write_thread(struct uart_8250_port *up,
-				     struct nbcon_write_context *wctxt)
-{
-	struct uart_8250_em485 *em485 = up->em485;
-	struct uart_port *port = &up->port;
-	unsigned int ier;
-
-	touch_nmi_watchdog();
-
-	if (!nbcon_enter_unsafe(wctxt))
-		return;
-
-	/* First save IER then disable the interrupts. */
-	ier = serial_port_in(port, UART_IER);
-	serial8250_clear_IER(up);
-
-	/* Check scratch reg if port powered off during system sleep. */
-	if (up->canary && (up->canary != serial_port_in(port, UART_SCR))) {
-		serial8250_console_restore(up);
-		up->canary = 0;
-	}
-
-	if (em485) {
-		if (em485->tx_stopped)
-			up->rs485_start_tx(up);
-		mdelay(port->rs485.delay_rts_before_send);
-	}
-
-	if (nbcon_exit_unsafe(wctxt)) {
-		int len = READ_ONCE(wctxt->len);
-		int i;
-
-		/*
-		 * Write out the message. Toggle unsafe for each byte in order
-		 * to give another (higher priority) context the opportunity
-		 * for a friendly takeover. If such a takeover occurs, this
-		 * context must reacquire ownership in order to perform final
-		 * actions (such as re-enabling the interrupts).
-		 *
-		 * IMPORTANT: wctxt->outbuf and wctxt->len are no longer valid
-		 *	      after a reacquire so writing the message must be
-		 *	      aborted.
-		 */
-		for (i = 0; i < len; i++) {
-			if (!nbcon_enter_unsafe(wctxt)) {
-				nbcon_reacquire_nobuf(wctxt);
-				break;
-			}
-
-			uart_console_write(port, wctxt->outbuf + i, 1, serial8250_console_putchar);
-
-			if (!nbcon_exit_unsafe(wctxt)) {
-				nbcon_reacquire_nobuf(wctxt);
-				break;
-			}
-		}
-	} else {
-		nbcon_reacquire_nobuf(wctxt);
-	}
-
-	while (!nbcon_enter_unsafe(wctxt))
-		nbcon_reacquire_nobuf(wctxt);
-
-	/* Finally, wait for transmitter to become empty and restore IER. */
-	wait_for_xmitr(up, UART_LSR_BOTH_EMPTY);
-	if (em485) {
-		mdelay(port->rs485.delay_rts_after_send);
-		if (em485->tx_stopped)
-			up->rs485_stop_tx(up);
-	}
-	serial_port_out(port, UART_IER, ier);
-
-	/*
-	 * The receive handling will happen properly because the receive ready
-	 * bit will still be set; it is not cleared on read.  However, modem
-	 * control will not, we must call it if we have saved something in the
-	 * saved flags while processing with interrupts off.
-	 */
-	if (up->msr_saved_flags)
-		serial8250_modem_status(up);
-
-	nbcon_exit_unsafe(wctxt);
-}
-
-void serial8250_console_write_atomic(struct uart_8250_port *up,
-				     struct nbcon_write_context *wctxt)
-{
-	struct uart_port *port = &up->port;
-	unsigned int ier;
-
-	/* Atomic console not supported for rs485 mode. */
-	if (WARN_ON_ONCE(up->em485))
-		return;
-
-	touch_nmi_watchdog();
-
-	if (!nbcon_enter_unsafe(wctxt))
-		return;
-
-	/*
-	 * First save IER then disable the interrupts. The special variant to
-	 * clear IER is used because atomic printing may occur without holding
-	 * the port lock.
-	 */
-	ier = serial_port_in(port, UART_IER);
-	__serial8250_clear_IER(up);
-
-	/* Check scratch reg if port powered off during system sleep. */
-	if (up->canary && (up->canary != serial_port_in(port, UART_SCR))) {
-		serial8250_console_restore(up);
-		up->canary = 0;
-	}
-
-	if (up->console_newline_needed)
-		uart_console_write(port, "\n", 1, serial8250_console_putchar);
-	uart_console_write(port, wctxt->outbuf, wctxt->len, serial8250_console_putchar);
-
-	/* Finally, wait for transmitter to become empty and restore IER. */
-	wait_for_xmitr(up, UART_LSR_BOTH_EMPTY);
-	serial_port_out(port, UART_IER, ier);
-
-	nbcon_exit_unsafe(wctxt);
-}
-#endif /* CONFIG_SERIAL_8250_LEGACY_CONSOLE */
 
 static unsigned int probe_baud(struct uart_port *port)
 {
@@ -3589,7 +3439,6 @@ static unsigned int probe_baud(struct uart_port *port)
 
 int serial8250_console_setup(struct uart_port *port, char *options, bool probe)
 {
-	struct uart_8250_port *up = up_to_u8250p(port);
 	int baud = 9600;
 	int bits = 8;
 	int parity = 'n';
@@ -3599,8 +3448,6 @@ int serial8250_console_setup(struct uart_port *port, char *options, bool probe)
 	if (!port->iobase && !port->membase)
 		return -ENODEV;
 
-	up->console_newline_needed = false;
-
 	if (options)
 		uart_parse_options(options, &baud, &parity, &bits, &flow);
 	else if (probe)

include/linux/serial_8250.h

@@ -153,8 +153,6 @@ struct uart_8250_port {
 #define MSR_SAVE_FLAGS UART_MSR_ANY_DELTA
 	unsigned char		msr_saved_flags;
 
-	bool			console_newline_needed;
-
 	struct uart_8250_dma	*dma;
 	const struct uart_8250_ops *ops;
 
@@ -206,10 +204,6 @@ void serial8250_init_port(struct uart_8250_port *up);
 void serial8250_set_defaults(struct uart_8250_port *up);
 void serial8250_console_write(struct uart_8250_port *up, const char *s,
 			      unsigned int count);
-void serial8250_console_write_atomic(struct uart_8250_port *up,
-				     struct nbcon_write_context *wctxt);
-void serial8250_console_write_thread(struct uart_8250_port *up,
-				     struct nbcon_write_context *wctxt);
 int serial8250_console_setup(struct uart_port *port, char *options, bool probe);
 int serial8250_console_exit(struct uart_port *port);