On Mon, Nov 09, 2026 at 04:27:31PM +0000, James Clark wrote:
On 16/10/2026 17:55, Leo Yan wrote:
The Arm ARM (ARM DDI 0487 M.c) rule RDJMDD says:
| When the following conditions apply, the PE might ignore a direct or | external write to any of certain Trace Buffer Unit registers, other | than a direct write or external write to TRBLIMITR_EL1 that clears | the conditions: | • TRBLIMITR_EL1.E is 1, and either FEAT_TRBE_EXT is not implemented | or the Trace Buffer Unit is using Self-hosted mode.
Doesn't the rule just say that the buffer must be disabled before doing writes to other registers? But the explanation for removing the extra disable is that it's already disabled at this point, so nothing changes.
The commit message would be clearer without this bit IMO. There's no architectural requirement to make this change, it's only a software one.
The rule reference was intended to provide context. The main purpose is to clarify the rule remains satisfied with this patch.
I will refine the commit log to make it clear.
Thanks, Leo