On Mon, Mar 17, 2025 at 03:05:41PM +0000, James Clark wrote:
[...]
/*
- coresight_disclaim_device_unlocked : Clear the claim tag for the device.
- Clear the claim tag for the device.
- Returns an error if the device wasn't already claimed.
- */
+int coresight_reset_claim(struct csdev_access *csa) +{
int ret;CS_UNLOCK(csa->base);ret = coresight_reset_claim_unlocked(csa);CS_LOCK(csa->base);return ret;+} +EXPORT_SYMBOL_GPL(coresight_reset_claim);
Maybe my question is overlapping with Mike's comment.
Callers never check the return values from coresight_reset_claim(). I am
I can remove the return value if it's confusing. The thought process was probably that it could be useful somewhere in the future, and coresight_reset_claim_unlocked() returns something anyway so might as well pass it up.
wandering if coresight_reset_claim() can directly call coresight_clear_self_claim_tag() for _trying_ to clear self-host tag in probe phase. Any self claim tag issues will be deferred to detect until enable the component.
Maybe, the spec does a read before setting which I assumed should be done for clearing as well.
If you mean PSCI doc, the flow for claiming tag is a handshake between self-host software and external debugger, this is why a read is required.
For a cleaning up, it is not about syncing with external debugger. And writing bit 0 to TRCCLAIMCLR will not impact external debugger. So I don't think a read prior to cleaning self claim tag is needed.
As in to not touch anything if it's in use externally. It doesn't specifically describe any clearing sequence, but if we assume it's ok to blindly clear self hosted flag even when it's in use then yes we can directly call coresight_clear_self_claim_tag().
As a result, directly calling coresight_clear_self_claim_tag() works for me.
Thanks, Leo