Re: platform/x86/intel/pmc: regression found in commit 804951203aa541ad6720c9726c173d18aeb3ab6b

[James Hutchinson]

No problems - have logged this in Bugzilla as #218143:

https://bugzilla.kernel.org/show_bug.cgi?id=218143

Regards,
James.

On Mon, 13 Nov 2023 at 18:04, Box, David E <david.e.box@xxxxxxxxx> wrote:
>
> Hi James,
>
> Can you file a bug at https://bugzilla.kernel.org/ under Power Management? Let us know what the bug number is. Thanks.
>
> David
> ________________________________
> From: James Hutchinson <jahutchinson99@xxxxxxxxxxxxxx>
> Sent: Monday, November 13, 2023 7:42 AM
> To: Pardee, Xi <xi.pardee@xxxxxxxxx>; rajneesh bhardwaj <irenic.rajneesh@xxxxxxxxx>; Box, David E <david.e.box@xxxxxxxxx>; ilpo.jarvinen@xxxxxxxxxxxxxxx <ilpo.jarvinen@xxxxxxxxxxxxxxx>; hdegoede@xxxxxxxxxx <hdegoede@xxxxxxxxxx>
> Cc: platform-driver-x86@xxxxxxxxxxxxxxx <platform-driver-x86@xxxxxxxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx <linux-kernel@xxxxxxxxxxxxxxx>
> Subject: platform/x86/intel/pmc: regression found in commit 804951203aa541ad6720c9726c173d18aeb3ab6b
>
> Running here on an Intel NUC 8i3BEH Coffee Lake machine under Arch Linux.
>
> Connected to this machine I have 4x USB DVB Cards (2xDVBSky S960
> DVB-S2 adapters & 2xGeniatech T230 DVB-T2 adapters), and I stream TV
> Channels around the house via Tvheadend.
>
> Since linux kernel v6.5 onwards I noticed a bad performance regression
> whereby the streams are basically unstable. There are tons of
> continuity errors in the Tvheadend logfile, and the picture and sound
> are badly broken up as though the system is throttled or does not have
> the bandwidth to cope with the streams.
>
> Sometimes the stream will work for a minute or so after reboot, before
> then becoming unstable, and then seems to remain unstable until the
> next cold reboot.
>
> I dropped back to v6.1 LTS (where everything is fine) and re-tested
> following the release of v6.6...
> ...the problem had not gone away so I performed a git bisect to
> identify the culprit and found this to be:
>
> 804951203aa541ad6720c9726c173d18aeb3ab6b: platform/x86:intel/pmc:
> Combine core_init() and core_configure()
>
> I can work around the issue by either reverting this commit or by
> disabling CONFIG_INTEL_PMC_CORE and rebuilding the kernel manually,
> either of which results in perfect DVB streaming once more.
>
> Happy to test any potential patches or otherwise provide further
> information as required.
>
>
> James.