[Bug 2142336] Re: Coresight fails to build on 6.8.0-101 due to 'atomic_t' member accessed as 'int'

This bug is awaiting verification that the linux-nvidia-
tegra/6.8.0-1018.18 kernel in -proposed solves the problem. Please test
the kernel and update this bug with the results. If the problem is
solved, change the tag 'verification-needed-noble-linux-nvidia-tegra' to
'verification-done-noble-linux-nvidia-tegra'. If the problem still
exists, change the tag 'verification-needed-noble-linux-nvidia-tegra' to
'verification-failed-noble-linux-nvidia-tegra'.


If verification is not done by 5 working days from today, this fix will
be dropped from the source code, and this bug will be closed.


See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how
to enable and use -proposed. Thank you!


** Tags added: kernel-spammed-noble-linux-nvidia-tegra-v2 verification-needed-noble-linux-nvidia-tegra

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https://bugs.launchpad.net/bugs/2142336

Title:
Coresight fails to build on 6.8.0-101 due to 'atomic_t' member
accessed as 'int'

Status in linux package in Ubuntu:
New
Status in linux source package in Noble:
New

Bug description:
SRU Justification:

[Impact]

When CONFIG_CORESIGHT is enabled, noble 6.8.0-101 fails to build with
the following errors:

```
drivers/hwtracing/coresight/coresight-catu.c: In function 'catu_enable':
drivers/hwtracing/coresight/coresight-catu.c:465:27: error: invalid operands to binary == (have 'atomic_t' and 'int')
  465 | if (csdev->refcnt == 0) {
      | ~~~~~~~~~~~~~ ^~
      | |
      | atomic_t
drivers/hwtracing/coresight/coresight-catu.c:471:30: error: wrong type argument to increment
  471 | csdev->refcnt++;
      | ^~
drivers/hwtracing/coresight/coresight-catu.c: In function 'catu_disable':
drivers/hwtracing/coresight/coresight-catu.c:498:13: error: wrong type argument to decrement
  498 | if (--csdev->refcnt == 0) {
      | ^~
```

These errors are a result of including the following patch in upstream stable
updates, but missing some dependencies from the original patch set:

  Error description: refcnt accessed as int but defined as atomic_t
  Break commit: n/linux 0e2198d37507 ("coresight: catu: Introduce refcount and spinlock for enabling/disabling")
  Missing commit: 4545b38ef004 ("coresight: Remove atomic type from refcnt")
  Patch series: "coresight: Separate sysfs and Perf usage and some other cleanups"
                (https://lists.infradead.org/pipermail/linux-arm-kernel/2024-January/899269.html)

[Fix]

Cherry-pick upstream commit:
4545b38ef004 ("coresight: Remove atomic type from refcnt")
which requires a few context fixups due to missing commits from the original
patchset. Those missing patches are not required for this commit, so we can
just fix and apply it alone to reduce the number of changes.

NOTE: These are the missing dependent patches for a clean application:

a0fef3f05cf3 ("coresight: Make language around "activated" sinks consistent")
a11ebe138b8d ("coresight: Remove ops callback checks")
9cae77cf23e3 ("coresight: Move mode to struct coresight_device")
d5e83f97eb56 ("coresight: Remove the 'enable' field.")
1f5149c7751c ("coresight: Move all sysfs code to sysfs file")

These contain pretty significant refactoring and cleanup (although they don't
alter behaviour) so they were omitted to reduce changes to a stable kernel.

[Test Plan]

Ensure CONFIG_CORESIGHT and CONFIG_CORESIGHT_CATU are enabled, then
compile test.

[Where problems could occur]

There is a low chance of regression since this patch is purely cleanup and
does not modify observable behaviour, as stated by the author in the original
patch set. Additionally, coresight failed to build before this, so this is
a guaranteed improvement in that respect. There is a risk of breakage if I
missed some dependent commits, or if my fixups were incorrect.

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