Date:   Fri, 3 Mar 2023 18:54:23 +1100
From:   Orlando Chamberlain <orlandoch.dev@gmail.com>
To:     Hans de Goede <hdegoede@redhat.com>
Cc:     Mark Gross <markgross@kernel.org>,
        platform-driver-x86@vger.kernel.org, linux-kernel@vger.kernel.org,
        Lukas Wunner <lukas@wunner.de>,
        Seth Forshee <sforshee@kernel.org>,
        Aditya Garg <gargaditya08@live.com>,
        Aun-Ali Zaidi <admin@kodeit.net>,
        Kerem Karabay <kekrby@gmail.com>
Subject: Re: [PATCH v3 0/5] apple-gmux: support MMIO gmux type on T2 Macs
Message-ID: <20230303185423.30bd115f@redecorated-mbp>
In-Reply-To: <4ccb9139-1e70-e669-646a-1975460962cd@redhat.com>
References: <20230218132007.3350-1-orlandoch.dev@gmail.com>
        <4ccb9139-1e70-e669-646a-1975460962cd@redhat.com>
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Hi Hans,

On Wed, 1 Mar 2023 13:54:37 +0100
Hans de Goede <hdegoede@redhat.com> wrote:

> Hi,
> 
> On 2/18/23 14:20, Orlando Chamberlain wrote:
> > Hi All,
> > 
> > This patch series adds support for the MMIO based gmux present on
> > these Dual GPU Apple T2 Macs: MacBookPro15,1, MacBookPro15,3,
> > MacBookPro16,1, MacBookPro16,4 (although amdgpu isn't working on
> > MacBookPro16,4 [1]).
> > 
> > Changes from v2[2]:
> > 
> > - Add "," to last item in apple_gmux_type enum
> > - Don't not clear interrupts when status is 0
> > - Don't check if we failed to make debugfs folder
> > - Check for fake mmio gmux  
> 
> Thanks, this looks good to me now:
> 
> Reviewed-by: Hans de Goede <hdegoede@redhat.com>
> 
> for the entire series.
> 
> Can you prepare a v4 addressing Lukas's remarks:
> 
> 1. Switch to acpi_execute_simple_method()
> 2. Add extra info about the gmux provided by Lukas 
>    to either the docs or as comments
> 
> With those changes added I believe v4 will be ready
> for merging.

Good to hear, I'll try to send out a v4 tonight.

> 
> Regards,
> 
> Hans
> 
> 
> > 
> > # 1:
> > 
> > has a slight change in how the switch state is read: instead of
> > checking for x == 2, check !(x & 1)
> > 
> > # 2:
> > 
> > implements a system to support more than 2 gmux types
> > 
> > # 3:
> > 
> > start using the gmux's GMSP acpi method when handling interrupts on
> > MMIO gmux's. This is needed for the MMIO gmux's to clear interrupts.
> > 
> > # 4:
> > 
> > Adds support for the MMIO based gmux on T2 macs.
> > 
> > # 5:
> > 
> > Add a debugfs interface to apple-gmux so data from ports can be read
> > and written to from userspace.
> > 
> > This can be used for more easily researching what unknown ports do,
> > and switching gpus when vga_switcheroo isn't ready (e.g. when one
> > gpu is bound to vfio-pci and in use by a Windows VM, I can use this
> > to switch my internal display between Linux and Windows easily).
> > 
> > # Issues:
> > 
> > 1. Switching gpus at runtime has the same issue as indexed gmux's:
> > the inactive gpu can't probe the DDC lines for eDP [3]
> > 
> > 2. iMacPro1,1, iMac20,1 and iMac20,2 all seem to have a gmux in
> > their acpi tables, but they shouldn't. A check that hopefully will
> > detect this is used, but it's untested as I don't have any of those
> > computers.
> > 
> > 3. Powering on the amdgpu with vga_switcheroo doesn't work well. I'm
> > told on the MacBookPro15,1 it works sometimes, and adding delays
> > helps, but on my MacBookPro16,1 I haven't been able to get it to
> > work at all:
> > 
> > amdgpu: switched off
> > amdgpu: switched on
> > amdgpu 0000:03:00.0:
> >     Unable to change power state from D3hot to D0, device
> > inaccessible amdgpu 0000:03:00.0:
> >     Unable to change power state from D3cold to D0, device
> > inaccessible [drm] PCIE GART of 512M enabled (table at
> > 0x00000080FEE00000). [drm] PSP is resuming...
> > [drm:psp_hw_start [amdgpu]] *ERROR* PSP create ring failed!
> > [drm:psp_resume [amdgpu]] *ERROR* PSP resume failed
> > [drm:amdgpu_device_fw_loading [amdgpu]]
> >     *ERROR* resume of IP block <psp> failed -62
> > amdgpu 0000:03:00.0: amdgpu: amdgpu_device_ip_resume failed (-62).
> > snd_hda_intel 0000:03:00.1: Enabling via vga_switcheroo
> > snd_hda_intel 0000:03:00.1:
> >     Unable to change power state from D3cold to D0, device
> > inaccessible snd_hda_intel 0000:03:00.1: CORB reset timeout#2,
> > CORBRP = 65535 snd_hda_codec_hdmi hdaudioC0D0: Unable to sync
> > register 0x2f0d00. -5
> > 
> > There are some acpi methods (PWRD, PWG1 [4, 5]) that macOS calls
> > when changing the amdgpu's power state, but we don't use them and
> > that could be a cause. Additionally unlike previous generation
> > Macbooks which work better, on MacBookPro16,1 the gpu is located
> > behind 2 pci bridges:
> > 
> > 01:00.0 PCI bridge: Advanced Micro Devices, Inc. [AMD/ATI]
> >     Navi 10 XL Upstream Port of PCI Express Switch (rev 43)
> > 02:00.0 PCI bridge: Advanced Micro Devices, Inc. [AMD/ATI]
> >     Navi 10 XL Downstream Port of PCI Express Switch
> > 03:00.0 VGA compatible controller: Advanced Micro Devices, Inc.
> > [AMD/ATI] Navi 14 [Radeon RX 5500/5500M / Pro 5500M] (rev 43)
> > 03:00.1 Audio device: Advanced Micro Devices, Inc. [AMD/ATI]
> >     Navi 10 HDMI Audio
> > 
> > Upon attempting to power on the gpu with vga_switcheroo, all these
> > devices except 01:00.0 have their config space filled with 1s.
> > Rescanning pci makes the config space of all the devices go back to
> > normal, however amdgpu still fails to resume with the same logs as
> > above.
> > 
> > [1]:
> > https://lore.kernel.org/all/3AFB9142-2BD0-46F9-AEA9-C9C5D13E68E6@live.com/
> > [2]:
> > https://lore.kernel.org/platform-driver-x86/20230216122342.5918-1-orlandoch.dev@gmail.com/
> > [3]:
> > https://lore.kernel.org/all/9eed8ede6f15a254ad578e783b050e1c585d5a15.1439288957.git.lukas@wunner.de/
> > [4]:
> > https://gist.github.com/Redecorating/6c7136b7a4ac7ce3b77d8e41740dd87b
> > [5]:
> > https://lore.kernel.org/all/20120710160555.GA31562@srcf.ucam.org/
> > 
> > Orlando Chamberlain (5):
> >   apple-gmux: use first bit to check switch state
> >   apple-gmux: refactor gmux types
> >   apple-gmux: Use GMSP acpi method for interrupt clear
> >   apple-gmux: support MMIO gmux on T2 Macs
> >   apple-gmux: add debugfs interface
> > 
> >  drivers/platform/x86/apple-gmux.c | 349
> > ++++++++++++++++++++++++++---- include/linux/apple-gmux.h        |
> > 70 ++++-- 2 files changed, 357 insertions(+), 62 deletions(-)
> >   
>