Merge tag 'printk-for-6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux

Pull printk updates from Petr Mladek:

 - New option "printk.debug_non_panic_cpus" allows to store printk
   messages from non-panic CPUs during panic. It might be useful when
   panic() fails. It is disabled by default because it increases the
   chance to see the messages printed before panic() and on the
   panic-CPU.

 - New build option "CONFIG_NULL_TTY_DEFAULT_CONSOLE" allows to build
   kernel without the virtual terminal support which prefers ttynull
   over serial console.

 - Do not unblank suspended consoles.

 - Some code clean up.

* tag 'printk-for-6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
  printk/panic: Add option to allow non-panic CPUs to write to the ring buffer.
  printk: Add an option to allow ttynull to be a default console device
  printk: Check CON_SUSPEND when unblanking a console
  printk: Rename console_start to console_resume
  printk: Rename console_stop to console_suspend
  printk: Rename resume_console to console_resume_all
  printk: Rename suspend_console to console_suspend_all

3 files changed, 23 insertions, 6 deletions

diff --git a/drivers/gpu/drm/clients/drm_log.c b/drivers/gpu/drm/clients/drm_log.c
index 379850c83e51..d239f1e3c456 100644
--- a/drivers/gpu/drm/clients/drm_log.c
+++ b/drivers/gpu/drm/clients/drm_log.c
@@ -323,7 +323,7 @@ static int drm_log_client_suspend(struct drm_client_dev *client, bool _console_l
 {
 	struct drm_log *dlog = client_to_drm_log(client);
 
-	console_stop(&dlog->con);
+	console_suspend(&dlog->con);
 
 	return 0;
 }
@@ -332,7 +332,7 @@ static int drm_log_client_resume(struct drm_client_dev *client, bool _console_lo
 {
 	struct drm_log *dlog = client_to_drm_log(client);
 
-	console_start(&dlog->con);
+	console_resume(&dlog->con);
 
 	return 0;
 }
diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig
index 63a494d36a1f..7fb81bbaee60 100644
--- a/drivers/tty/Kconfig
+++ b/drivers/tty/Kconfig
@@ -383,7 +383,24 @@ config NULL_TTY
 	  available or desired.
 
 	  In order to use this driver, you should redirect the console to this
-	  TTY, or boot the kernel with console=ttynull.
+	  TTY, boot the kernel with console=ttynull, or enable
+	  NULL_TTY_DEFAULT_CONSOLE.
+
+	  If unsure, say N.
+
+config NULL_TTY_DEFAULT_CONSOLE
+	bool "Support for console on ttynull"
+	depends on NULL_TTY=y && !VT_CONSOLE
+	help
+	  Say Y here if you want the NULL TTY to be used as a /dev/console
+	  device by default.
+
+	  For example, it might be useful to prevent a VT-less kernel from
+	  writing the system log to a random device connected to the serial
+	  port.
+
+	  Another console driver still might get preferred via the command
+	  line, SPCR, or the device tree.
 
 	  If unsure, say N.
 
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 92f7e752f862..d46650e578e5 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -2426,10 +2426,10 @@ int uart_suspend_port(struct uart_driver *drv, struct uart_port *uport)
 	}
 
 	/*
-	 * Disable the console device before suspending.
+	 * Suspend the console device before suspending the port.
 	 */
 	if (uart_console(uport))
-		console_stop(uport->cons);
+		console_suspend(uport->cons);
 
 	uart_change_pm(state, UART_PM_STATE_OFF);
 
@@ -2484,7 +2484,7 @@ int uart_resume_port(struct uart_driver *drv, struct uart_port *uport)
 			uart_port_unlock_irq(uport);
 		}
 		if (console_suspend_enabled)
-			console_start(uport->cons);
+			console_resume(uport->cons);
 	}
 
 	if (tty_port_suspended(port)) {