kernel: Add a patch to fix an NPD when using the UART and a stuck irq

[ukleinek]

When /dev/ttySTM1 is closed while there are still some characters pending to be sent, the kernel dereferences a null pointer which locks up the kernel.

Fix that by picking a patch from today's linux-next.

While the commit log claims this indeed fixes the problem noticed by @SmithChart, this isn't tested yet.

[hnez]

This seems to solve part of the problem. The good thing is that the kernel errors seen when closing a /dev/ttySTM* while there is still pending data is gone and now there is only a:

$ dmesg -w
…
[   68.147733] stm32-usart 4000f000.serial: Transmission is not complete
…

in its place.

But it gets worse when one tries to use the device again:

$ dmesg -w
…
[   78.434633] panel-mipi-dbi-spi spi2.0: SPI transfer timed out
[   78.439387] spi_master spi2: failed to transfer one message from queue
[   78.450284] spi_master spi2: noqueue transfer failed
[   78.454254] panel-mipi-dbi-spi spi2.0: error -110 when sending command 0x2a
[   78.461289] lmp92064 spi1.0: SPI transfer timed out
…

followed by a watchdog induced reboot.

To me this looks like e.g. lower-priority interrupts no longer being handled.

[SmithChart]

followed by a watchdog induced reboot.
To me this looks like e.g. lower-priority interrupts no longer being handled.

What @hnez reports still sounds like the behavior I've observed.

[ukleinek]

Closed by mistake, I think by accidentally pushing a wrong rev to my branch. Anyhow, now it should be right and fixed.

[hnez]

I've tested this PR now and it looks like it fixes the issues we had. Nice to see this endeavour come to an end!

Before we merge it however #136 should be merged first and this PR be rebased so that the version number consistency check does not throw errors.

[SmithChart]

#136 has been merged. Please rebase.

[ukleinek]

I don't know what the version consistency check is about, but I rebased anyhow.

[ukleinek]

(Pushed once more because I got the committer info wrong in the first force-push)

[hnez]

I don't know what the version consistency check is about, but I rebased anyhow.

It makes sure that we do not generate any images containing e.g. 24.04 as a version number after the 24.04 version tag is already set and instead have 24.04+dev as a version in meta-lxatac-software/conf/distro/tacos.conf.

PS: I've accidentially pressed "Close with comment" instead of "Cancel". When I decided that I did not want to add this comment. As a result I've added the comment in a half-ready state and closed the PR, both of which I did not mean to do. Oh my.