On Mon, 20 Feb 2023 10:20:48 +0100 Lukas Wunner <lukas@xxxxxxxxx> wrote: > On Sun, Feb 19, 2023 at 12:20:06AM +1100, Orlando Chamberlain wrote: > > --- a/drivers/platform/x86/apple-gmux.c > > +++ b/drivers/platform/x86/apple-gmux.c > > @@ -28,15 +28,17 @@ > > * DOC: Overview > > * > > * gmux is a microcontroller built into the MacBook Pro to support > > dual GPUs: > > - * A `Lattice XP2`_ on pre-retinas, a `Renesas R4F2113`_ on > > retinas. > > + * A `Lattice XP2`_ on pre-retinas, a `Renesas R4F2113`_ on pre-T2 > > retinas. > > + * The chip used on T2 Macs is not known. > > I've just taken a look at the schematics of the MBP16,1 and it turns > out that T2 *is* the gmux. The chip is called H9M. The interaction > with the OS is through that MMIO area. > > There's a GPIO expander attached to T2 via I2C (NXP PCAL6524), > probably because they didn't have enough GPIO pins available on T2 > itself. The GPIO expander enables/disables the voltage regulators of > the discrete GPU, hence can cut power to it. It also drives panel > power and has a GPIO to switch the mux. > > The mux is an NXP CBTL06142 as on previous models. Thanks for figuring that all out, I can add that to the documentation. > > Thanks, > > Lukas
