Re: [PATCH 0/3] ACPI: video/apple-gmux: Improve apple-gmux backlight detection

[Lukas Wunner <lukas@wunner.de>]

On Mon, Jan 23, 2023 at 01:38:37PM +0100, Hans de Goede wrote:
> On 1/23/23 13:09, Lukas Wunner wrote:
> > On Mon, Jan 23, 2023 at 12:37:47PM +0100, Hans de Goede wrote:
> > > Some apple laptop models have an ACPI device with a HID of APP000B
> > > and that device has an IO resource (so it does not describe the new
> > > unsupported MMIO based gmux type), but there actually is no gmux
> > > in the laptop at all.
> > >
> > > This patch-series improves the drivers/acpi/video_detect.c so that
> > > it no longer tries to use the non present gmux in this case.
> > >
> > > Note I'm still waiting for testing feedback from the reporter of
> > > this problem. But from the logs the problem is clear
> > > (the logs show: "apple_gmux: gmux device not present")
> > 
> > Please provide a link to the original report.  I would also like to
> > know the exact MacBook model used and I would like to see full dmesg
> > output as well as an acpidump.
> 
> I only have a report by private email. This does include full dmesg
> output and an acpidump. I will forward this to you in a private
> email.
> 
> The reporter describes their model as a macbookpro8,1.
> 
> > What you're saying here is that there's a fake APP000B device present
> > in DSDT
> 
> Yes that is exactly what I'm saying.

That's a 2011 13" MacBook Pro which indeed does not have dual GPUs.

I searched for other affected models and this seems to be more common
than I thought:

MacBookPro5,4
https://pastebin.com/8Xjq7RhS

MacBookPro8,1
https://linux-hardware.org/?probe=e513cfbadb&log=dmesg

MacBookPro9,2
https://bugzilla.kernel.org/attachment.cgi?id=278961

MacBookPro10,2
https://lkml.org/lkml/2014/9/22/657

MacBookPro11,2
https://forums.fedora-fr.org/viewtopic.php?id=70142

MacBookPro11,4
https://raw.githubusercontent.com/im-0/investigate-card-reader-suspend-problem-on-mbp11.4/master/test-16/dmesg

These are 13" and 15" models from the pre-retina and retina era
(2009 - 2015).  None of them have dual GPUs.  (Only a subset of
the 15" and 17" models had dual GPUs.)  Apple sloppily included
a GMUX device on all of them and it wasn't a problem so far
because the gmux driver detects non-presence and bails out,
but it throws off the new backlight algorithm.

This is really sad. :(

Please add a Reported-by to your commits as well as the list I've
provided above so that we've got a complete record in the git history.

Thanks,

Lukas