1 Oct
2025
1 Oct
'25
4:55 p.m.
On Wed, Oct 01, 2025 at 01:15:01PM +0100, Mike Leach wrote:
[...]
If the firmware is PSCI compliant there is no need to save/restore the context within the kernel driver if the external claim bit is set?
Yes, this is my conclusion.
A strong reason is that an external debugger should work even without the ETM driver.
In the current implementation [1], the ETMv4 driver saves and restores the claim bit only in sysfs or perf modes, which means it does not serve the case where an external debugger has already claimed the device.
Thanks, Leo
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/driv...