[PATCH] coresight-tmc: Add configurable timeout for flush and tmcready

[Yuanfang Zhang]

On 6/30/2025 7:08 PM, Leo Yan wrote:
> On Mon, Jun 30, 2025 at 06:40:53PM +0800, Yuanfang Zhang wrote:
> 
> [...]
> 
>>>>> The current implementation uses a fixed timeout via
>>>>> coresight_timeout(), which may be insufficient when multiple
>>>>> sources are enabled or under heavy load, leading to TMC
>>>>> readiness or flush completion timeout.
>>>
>>> I would suggest that we first make clear if this is a hardware quirk or
>>> a common issue in Arm CoreSight.
> 
>> sure, now this issue has been found that not only CPU ETM, but also subsystem ETM.
> 
> As the commit log states, "sources are enabled or under heavy load,
> leading to TMC readiness or flush completion timeout." I would like to
> confirm how this situation can happen.
> 
Enable all etms, then cat TMC without disable source.
> When disabling a CoreSight path, the driver follows a sequential
> order: the source device is disabled first, followed by flushing and
> disabling the TMC. We expect that there should be no contention
> between source devices and the sink when disabling the path. For a
> subsystem ETM, I expect we should also follow this sequence.
> 
> Leo
this issue is a different case: running cat tmc directly did not disable source.