On Thu, Dec 04, 2025 at 06:13:56PM +0530, Anshuman Khandual wrote:

On 01/12/25 4:51 PM, Leo Yan wrote:

quoted

set_trbe_disabled() should never appear in the enable flow, otherwise,
it may potentially hide bugs in the disable flow.

Remove set_trbe_disabled() from the enable path.

IIRC without first disabling TRBLIMITR_EL1_E - TRBE registers or their
fields should not be fetched or interpreted.

Yes. I think you are referring to the rule DJMDD in Arm ARM: "The PE
might ignore a direct or external write to any of certain Trace Buffer
Unit registers ... (when) TRBLIMITR_EL1.E is 1, and the Trace Buffer
Unit is using Self-hosted mode."

Without that none of the
subsequent HW operations should be performed inside trbe_enable_hw()
leading upto enabling it.

Fair enough.

If we can conclude the trace unit has been disabled properly in below
cases, no reason to arbitrarily calling set_trbe_disabled() during each
enable.

  1) The SYS_TRBLIMITR_EL1 register is cleared in trbe_reset_local()
     during probe phase.
  2) The SYS_TRBLIMITR_EL1.E bit is cleared in arm_trbe_irq_handler()
     for interrupt handling.
  3) The SYS_TRBLIMITR_EL1.E bit is cleared in the disable flow.


Seems to me, this is not only for code cleanup, we need to promise a
sane logic in the flow.

Thanks,
Leo