On Thu, Oct 14, 2021 at 10:01:53AM +0200, Francesco Dolcini wrote:

Hello Greg,

On Thu, Oct 14, 2021 at 09:33:55AM +0200, Greg Kroah-Hartman wrote:

quoted

On Thu, Oct 14, 2021 at 09:10:52AM +0200, Francesco Dolcini wrote:

quoted

From: Stefan Agner <stefan@agner.ch>

If the device used as a serial console gets un/re-binded, then
register_console() will call imx_uart_setup_console() again.
Drop __init so that imx_uart_setup_console() can be safely called
at runtime.

Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Francesco Dolcini <redacted>
---
 drivers/tty/serial/imx.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

What commit does this "fix"?

root@colibri-imx6ull-06746657:~# cat /sys/devices/virtual/tty/console/active 
tty1 ttymxc0
root@colibri-imx6ull-06746657:~# echo -n N > /sys/devices/virtual/tty/console/subsystem/ttymxc0/console
root@colibri-imx6ull-06746657:~# echo -n Y > /sys/devices/virtual/tty/console/subsystem/ttymxc0/console

struct console ->setup is called at that time, but imx_uart_console_setup() is gone ...

This specific way I described here to reproduce the issue was introduced with
 a3cb39d258ef serial: core: Allow detach and attach serial device for console

that is kernel 5.9+

(Andy added to to:)

But the original report was about bind/unbind of the uart driver, I guess this is possible since
way more time.

According to the original report from Stefan the issue is the same with unbind/bind of the console,
see https://marc.info/?l=linux-serial&m=154221779312036&w=2.

quoted

Should this go to stable kernels?  If so, how far back?

This is present also in 4.19 kernel, I feel like the issue is there since it is possible to unbind
a console driver (since ever considering the current LTS releases?). I could
investigate this a little bit more.

We have this patch in our kernel branch since 3 years but for some reason we never managed to upstream it.


Francesco

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel