[PATCH 1/2] coresight: ete: Always save state on power down

[Leo Yan]

On Tue, Apr 28, 2026 at 01:18:11PM +0100, James Clark wrote:
> ETE registers are always system registers so it's highly unlikely there
> will be an implementation that preserves them on CPU power down. Also
> the ETE DT binding never documented
> "arm,coresight-loses-context-with-cpu" so nobody would have legitimately
> been able to use that binding to fix it.
> 
> Fix it by hard coding the setting for ETE and add a warning if the user
> tried to use the module parameter. Don't add a warning if
> loses-context-with-cpu is present in the DT as it's not a documented
> binding anyway. etm4_init_pm_save() needs to happen after drvdata is
> initialised so etm4x_is_ete() can be called.
> 
> This fixes the following error when using Coresight with ACPI on the FVP
> which supports CPU PM:
> 
>   coresight ete0: External agent took claim tag
>   WARNING: drivers/hwtracing/coresight/coresight-core.c:248 at coresight_disclaim_device_unlocked+0xe0/0xe8, CPU#0: perf/117
> 
> Fixes: 35e1c9163e02 ("coresight: ete: Add support for ETE tracing")
> Signed-off-by: James Clark <james.clark at linaro.org>

Reviewed-by: Leo Yan <leo.yan at arm.com>