lowlatency kernel cannot use XDMA driver properly

[SYJ7895]

When I load the XDMA driver with a low-latency kernel on Ubuntu1604, a segmentation fault occurs when running run_test.sh. At this time, I can see the following information through dmesg:
BUG: scheduling while atomic: dma_from_device / 3266 / 0x00000000

[X-Ryl669]

This is likely an issue with the use of simple wait queues. Please try to use later kernel (at least 4.18 or better 5.0+) and report if it does not work.

[SYJ7895]

This is likely an issue with the use of simple wait queues. Please try to use later kernel (at least 4.18 or better 5.0+) and report if it does not work.

The "xdma_xfer_submit" function in libxdma.c calls "spin_lock (& engine-> desc_lock)" and then calls the "wait_event_interruptible_timeout" function with sleep nature. This caused the problem of "BUG: scheduling while atomic: dma_from_device / 3266 / 0x00000000" in the low-latency kernel, but there was no problem in the general kernel.

[hmaarrfk]

ive seen this in QDMA as well.

[chengts95]

Any suggestion to fix that?

[hmaarrfk]

Honestly, it could be related to: #49

I used aligned memory, and the problems lesssned (i think)

[chengts95]

On 5.3.15 x86_generic it will not cause this problem. It happens on my AARCH64 (kernel 4.9.140) board with RT patch. However, even on x86_generic the run_test.sh cannot work properly after I merged the 2 PRs.

[hmaarrfk]

I'm not sure. You should ping xilixn on their forums.

There was a XDMA driver written by others that fixed many aarch64 issues. It may fix yours.

It was on gitlab if I remember

[chengts95]

I suspect the usage of "swait.h" in this driver causes a lot of problems since the simple wait queue is "BROKEN wait queue" in the kernel now.

[bhathaway]

I have personally tested the fix on AARCH64. I would appreciate feedback on the following pull request, which I believe fixes this issue:

#50

[hmaarrfk]

Maybe keep this open until xilinx acknowledge s this?

[chengts95]

Still very buggy on my device, I think it is related to kernel version.

[hmaarrfk]

Hello,

My name is Mark Harfouche. I am not affiliated with Xilinx in any way. Over the
years of using QDMA, I've been wanted better community organization.

I've created a fork of dma_ip_drivers which I intend to maintain and work with the
community at large to improve.

The fork can be found https://github.com/hmaarrfk/dma_ip_drivers

For now, I am stating the main goals of the repository in
hmaarrfk#2

If you are interested in working together, feel free to open an issue or PR to
my fork.

Best,

Mark