This is a note to let you know that I've just added the patch titled
serial: 8250: Reinit port->pm on port specific driver unbind
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
serial-8250-reinit-port-pm-on-port-specific-driver-u.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 3fde69ed067a4361879da56c176701d2eb4e6f96
Author: Tony Lindgren <tony@xxxxxxxxxxx>
Date: Tue Apr 18 13:14:06 2023 +0300
serial: 8250: Reinit port->pm on port specific driver unbind
[ Upstream commit 04e82793f068d2f0ffe62fcea03d007a8cdc16a7 ]
When we unbind a serial port hardware specific 8250 driver, the generic
serial8250 driver takes over the port. After that we see an oops about 10
seconds later. This can produce the following at least on some TI SoCs:
Unhandled fault: imprecise external abort (0x1406)
Internal error: : 1406 [#1] SMP ARM
Turns out that we may still have the serial port hardware specific driver
port->pm in use, and serial8250_pm() tries to call it after the port
specific driver is gone:
serial8250_pm [8250_base] from uart_change_pm+0x54/0x8c [serial_base]
uart_change_pm [serial_base] from uart_hangup+0x154/0x198 [serial_base]
uart_hangup [serial_base] from __tty_hangup.part.0+0x328/0x37c
__tty_hangup.part.0 from disassociate_ctty+0x154/0x20c
disassociate_ctty from do_exit+0x744/0xaac
do_exit from do_group_exit+0x40/0x8c
do_group_exit from __wake_up_parent+0x0/0x1c
Let's fix the issue by calling serial8250_set_defaults() in
serial8250_unregister_port(). This will set the port back to using
the serial8250 default functions, and sets the port->pm to point to
serial8250_pm.
Signed-off-by: Tony Lindgren <tony@xxxxxxxxxxx>
Link: https://lore.kernel.org/r/20230418101407.12403-1-tony@xxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index d2df7d71d6667..a0325af2832a0 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -1125,6 +1125,7 @@ void serial8250_unregister_port(int line)
uart->port.type = PORT_UNKNOWN;
uart->port.dev = &serial8250_isa_devs->dev;
uart->capabilities = 0;
+ serial8250_init_port(uart);
serial8250_apply_quirks(uart);
uart_add_one_port(&serial8250_reg, &uart->port);
} else {
