linux-kernel - Re: [PATCH v2 4/5] apple-gmux: support MMIO gmux on T2 Macs

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Date:   Mon, 20 Feb 2023 10:24:02 +0100
From:   Lukas Wunner <lukas@...ner.de>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     Orlando Chamberlain <orlandoch.dev@...il.com>,
        Mark Gross <markgross@...nel.org>,
        platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
        Seth Forshee <sforshee@...nel.org>,
        Aditya Garg <gargaditya08@...e.com>,
        Aun-Ali Zaidi <admin@...eit.net>,
        Kerem Karabay <kekrby@...il.com>
Subject: Re: [PATCH v2 4/5] apple-gmux: support MMIO gmux on T2 Macs

On Mon, Feb 20, 2023 at 09:44:54AM +0100, Hans de Goede wrote:
> On 2/19/23 14:39, Lukas Wunner wrote:
> > I believe the Mac Pro (the trashcan one) also contains a gmux and
> > an APP000B device in DSDT.  I recall seeing a bug report due to a
> > splat in the gmux driver on that machine.  Back then I confirmed
> > in the schematics that it does contain a gmux, though I think it's
> > only used for brightness, not GPU switching.
> 
> Erm, the Mac Pro (the trashcan one) does not have an internal LCD
> panel, right?  So I don't think the gmux will be used for brightness
> control there ...

Right.  I see now that I even added a comment to apple-gmux.c on that
Mac Pro, I couldn't figure out back then what the gmux was for:

 * (The MacPro6,1 2013 also has a gmux, however it is unclear why since it has
 * dual GPUs but no built-in display.)

Thanks,

Lukas