TX2 serial port rt-flush not working anymore since jetson 32.7.4

The transition from 4.9.299 to 4.9.333 removed some code that was necessary for the rt-flush feature.

In particular the stable tree commit “e39085b8b75a4e328efa0ef5207c27d556d82fd7 tty: drop tty_schedule_flip()” was not ported properly.

This patch should fix this:
0001-tty-fix-rt-flush.patch.txt (1.6 KB)

Hi cbaumann,

Are you using the devkit or custom board for TX2?

Could you share the result of the following command on your board?

$ cat /etc/nv_tegra_release
$ uname -r

Do you mean this patch is missing and should be included in L4T R32.7.4?
Or it would cause any issue for tty?

Sorry for not being clear enough.

I am not really asking for help here. I am just pointing out an issue in the Nvidia Linux tree that I expect to be fixed in the next TX2 release (if there is any).

The issue is that UART rt-flush is not working anymore since 32.7.4 (e.g.: reading from a serial may block for a long time). The issue is resolved with the patch that I provided but maybe there is a better way to fix it.

We are using a custom board, but that doesn’t matter.

We are using a custom rootfs so there is no /etc/nv_tegra_release, but that doesn’t matter.

We are using the latest jetson release 32.7.4 so the kernel version is 4.9.337.

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