Subject: Re: Regression in split ARM MMIO timer driver

From: Marc Zyngier <[email-masked]>
Date: Sat, 09 May 2026 09:45:05 +0100

On Fri, 08 May 2026 20:48:14 +0100,
Jack Matthews <[email-masked]> wrote:
> 
> Hello,
> 
> I am working on mainlining an old chip, Qualcomm's MDM9625 modem.
> I had previously booted 6.17-rc3 before putting this project to the
> side, but when I restarted work on 7.0 I was unable to boot.

> I have bisected this to commit
> 0f67b56d84b4c49adfd61f19f81f84ec613ab51a
> (https://lore.kernel.org/all/[email-masked]/)
> and reverting this commit makes the device boot
> successfully. Unfortunately I do not have access to low level
> debugging such as UART so I have not been able to pinpoint exactly
> what is missing.

> My changes for this chip are all available here in case it is an
> issue of my own doing:
> https://github.com/jackmthws/linux/commits/mdm9625-latest/ I
> apologize if I this isn't the proper way to submit a regression
> report, this is my first time doing so.

Given that this is not a machine that is supported upstream, this
really isn't a regression. Unless of course you can reproduce it on
something that is currently supported, and in which case it would
absolutely be a regression.

I'm afraid that without a boot log, it is going to be difficult to
pinpoint what is going wrong here. This is most likely a latent bug
either in the MMIO timer driver, or something unexpected in the way
the platform is described.

Could you start by posting a kernel boot log of 7.0 with this commit
reverted? I'm also interested in finding out what happens if you don't
revert that commit, but instead comment out the entry in the Makefile
for the MMIO driver.

Thanks,

	M.

-- 
Jazz isn't dead. It just smells funny.