On Fri, Nov 21, 2025 at 12:23:50AM +0000, Kuan-Wei Chiu wrote:
[...]
I noticed this issue while browsing the coresight code after attending a technical talk on the subject. This code dates back to the initial driver submission over 10 years ago, so I was surprised it hadn't been caught earlier. Although I cannot perform runtime testing, the logic error seems obvious to me, so I still decided to submit this patch.
I have a question for maintainers.
The ETMv4 architecture specification shows that ETMv4 was released as a non-confidential module in May 2013 (with the confidential release even a year earlier). So ETMv4 has been a public IP for more than 12+ years, and ETMv3 has been gradually retired since then.
This fix can still be applied to older kernels, but seems to me that now might be an appropriate time to consider removing the ETMv3 driver from the mainline kernel?
Thanks, Leo
On 26/11/2025 12:09 pm, Leo Yan wrote:
On Fri, Nov 21, 2025 at 12:23:50AM +0000, Kuan-Wei Chiu wrote:
[...]
I noticed this issue while browsing the coresight code after attending a technical talk on the subject. This code dates back to the initial driver submission over 10 years ago, so I was surprised it hadn't been caught earlier. Although I cannot perform runtime testing, the logic error seems obvious to me, so I still decided to submit this patch.
I have a question for maintainers.
The ETMv4 architecture specification shows that ETMv4 was released as a non-confidential module in May 2013 (with the confidential release even a year earlier). So ETMv4 has been a public IP for more than 12+ years, and ETMv3 has been gradually retired since then.
This fix can still be applied to older kernels, but seems to me that now might be an appropriate time to consider removing the ETMv3 driver from the mainline kernel?
Thanks, Leo
Yeah, if anyone is using it it would be on an old kernel surely?
On Wed, Nov 26, 2025 at 12:11:05PM +0000, James Clark wrote:
[...]
This fix can still be applied to older kernels, but seems to me that now might be an appropriate time to consider removing the ETMv3 driver from the mainline kernel?
Yeah, if anyone is using it it would be on an old kernel surely?
We can confirm this in another way: if I don't miss anything, over the past several years (since 2017), we have not received any questions or bug reports based on hands-on practice regarding ETMv3 on the Coresight or perf mailing lists.
Thanks, Leo
Hi,
On Wed, 26 Nov 2025 at 12:31, Leo Yan leo.yan@arm.com wrote:
On Wed, Nov 26, 2025 at 12:11:05PM +0000, James Clark wrote:
[...]
This fix can still be applied to older kernels, but seems to me that now might be an appropriate time to consider removing the ETMv3 driver from the mainline kernel?
Yeah, if anyone is using it it would be on an old kernel surely?
We can confirm this in another way: if I don't miss anything, over the past several years (since 2017), we have not received any questions or bug reports based on hands-on practice regarding ETMv3 on the Coresight or perf mailing lists.
Thanks, Leo
The key to this is not the questions we are asked, but which platforms are still supported by the linux kernel.
The ETMv3 driver supports both ETMv3 and PTM trace (the programming model is the same, even if the trace decode is vastly different).
So as long as there are platforms supported that use either of those, we need to keep the driver in.
Mike
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James Clark -
Leo Yan -
Mike Leach