drm/panthor: Recover from panthor_gpu_flush_caches() failures

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: drm/panthor: Recover from panthor_gpu_flush_caches() failures We have seen a few cases where the whole memory subsystem is blocked and flush operations never complete. When that happens, we want to: - schedule a reset, so we can recover from this situation - in the reset path, we need to reset the pending_reqs so we can send new commands after the reset - if more panthor_gpu_flush_caches() operations are queued after the timeout, we skip them and return -EIO directly to avoid needless waits (the memory block won't miraculously work again) Note that we drop the WARN_ON()s because these hangs can be triggered with buggy GPU jobs created by the UMD, and there's no way we can prevent it. We do keep the error messages though. v2: - New patch v3: - Collect R-b - Explicitly mention the fact we dropped the WARN_ON()s in the commit message v4: - No changes

References

• https://git.kernel.org/stable/c/8ec4f1b14a6147db07d6e51aa1d6bcc799649847
• https://git.kernel.org/stable/c/57753f2c64c033a21a7400b3a2192db1cd6c890e
• https://git.kernel.org/stable/c/2c899c6026fc9d39286735b30c4d8550d4ea075b
• https://git.kernel.org/stable/c/3c0a60195b37af83bbbaf223cd3a78945bace49e