** Summary changed:

- black screen with cursor and on nouveau + i915
+ black screen with cursor on nouveau + i915

** Summary changed:

- black screen with cursor on nouveau + i915
+ black screen with cursor on dual nouveau + i915

** Description changed:

- This bug should be able to be reproduced on any computer with i915 +
- nouveau simultaneously modesetting, booting to stock gdm3 (wayland by
- default). My main example is a MacBookPro6,2 with the infamous GT 330m
- on 20.04 with -proposed enabled and booting with the following grub
- manipulations to set gmux to the integrated LVDS:
+ This bug should be able to be reproduced on any computer with both an
+ nvidia (stock nouveau) and intel igpu (stock i915), booting to stock
+ gdm3 (wayland by default). My main example is a MacBookPro6,2 with the
+ infamous GT 330m on 20.04 with -proposed enabled and booting with the
+ following grub manipulations to set gmux to the integrated LVDS:
  
  outb 0x710 2 - switch LVDS to intel
  outb 0x728 1 - switch internal DDC to intel
  outb 0x740 2 - switch displayport out to intel
  
  I am not using outb 0x750 0, so that the 330m remains powered on. It
  still works just fine-- the only thing broken is the LVDS connection to
  the internal panel. I disable it with video=LVDS-2:d.
  
  --> NOTE: This mod is only for the convenience of not having to deal
  with a phantom second screen once booted (both GPU's have the LVDS and
  edid of the internal screen hooked up). The computer boots fine and the
  bug reproduces exactly the same with or without it.
  
  I tested with all these modifications disabled, and this still occurred
  - it's not specific to my configuration. A user booting stock Ubuntu on
  this laptop, or as I discovered later, any nouveau + i915 hardware
  combination will run into this as well.
  
  Anyways, I'm keeping the 330m enabled to use DRI_PRIME to run
  applications on the 330m for good reason- it supports OpenGL 3.3 while
  HD Graphics (arrandale aka Ironlake) is the only HD Graphics iGPU stuck
  on OpenGL 2.1, thus otherwise vastly restricting the modern graphics
  workloads of the system.
  
  When explicitly booting with gdm3 WaylandEnable=false (login and desktop
  both xorg), everything works as expected - single screen driven by the
  i915's KMS, nouveau with DRI_PRIME working, returning NVA5 stats and
  functional with OpenGL 3 apps as well.
  
  On GDM3 wayland, however (by default-- which is why I think this bug is
  rather important), gdm3 starts to a black screen with cursor. The login
  screen and shell still seem to be running-- I can type my password
  blindly and press enter and the cursor freezes briefly as it does during
  a non-broken login. After a few seconds, I can press the volume up/down
  keys and I hear the volume sound. Pressing the app grid shortcut makes
  the cursor lag, just as it does when I disable the nvidia at the pcie
  link level and rendering works on i915. Backlight control also works on
  the login screen and once logged in. It's as if everything except the
  actual rendering to the screen is working.
  
  The minute I pass nouveau.modeset=0 in cmdline, or cut the power to the
  330m at the hardware level with outb 0x750, Wayland starts working
  again. The issue has something to do with GDM3's handling of a KMS-
  enabled nouveau GPU, whether it is headless or not (no difference with
  video=LVDS-2:d or not).
  
  To confirm my suspicions that it is not specific to the macbook pro
  line, this exact same issue (Xorg works wayland doesn't) also occurred
  on a desktop dual-gpu setup, with a GTX 760 (kepler) on nouveau tandem
  with a Haswell HD Graphics G3258-- with any combination of displays, all
  on the Intel, mixed on nvidia and intel, or all on nvidia, as long as
  both cards were modesetting, a black screen with cursor but blindly
  working gnome followed.
  
  This bug has existed since at least 19.04, if not earlier-- I replaced
  the nvidia gpu in that system with a Radeon 7870 when it ran that
  release due to this bug, as a matter of fact.

** Description changed:

  This bug should be able to be reproduced on any computer with both an
  nvidia (stock nouveau) and intel igpu (stock i915), booting to stock
  gdm3 (wayland by default). My main example is a MacBookPro6,2 with the
  infamous GT 330m on 20.04 with -proposed enabled and booting with the
  following grub manipulations to set gmux to the integrated LVDS:
  
  outb 0x710 2 - switch LVDS to intel
  outb 0x728 1 - switch internal DDC to intel
  outb 0x740 2 - switch displayport out to intel
  
  I am not using outb 0x750 0, so that the 330m remains powered on. It
  still works just fine-- the only thing broken is the LVDS connection to
  the internal panel. I disable it with video=LVDS-2:d.
  
  --> NOTE: This mod is only for the convenience of not having to deal
  with a phantom second screen once booted (both GPU's have the LVDS and
  edid of the internal screen hooked up). The computer boots fine and the
  bug reproduces exactly the same with or without it.
  
  I tested with all these modifications disabled, and this still occurred
  - it's not specific to my configuration. A user booting stock Ubuntu on
  this laptop, or as I discovered later, any nouveau + i915 hardware
  combination will run into this as well.
  
  Anyways, I'm keeping the 330m enabled to use DRI_PRIME to run
  applications on the 330m for good reason- it supports OpenGL 3.3 while
  HD Graphics (arrandale aka Ironlake) is the only HD Graphics iGPU stuck
  on OpenGL 2.1, thus otherwise vastly restricting the modern graphics
  workloads of the system.
  
  When explicitly booting with gdm3 WaylandEnable=false (login and desktop
  both xorg), everything works as expected - single screen driven by the
  i915's KMS, nouveau with DRI_PRIME working, returning NVA5 stats and
  functional with OpenGL 3 apps as well.
  
- On GDM3 wayland, however (by default-- which is why I think this bug is
+ On GDM3 wayland, however (the default-- which is why I think this bug is
  rather important), gdm3 starts to a black screen with cursor. The login
  screen and shell still seem to be running-- I can type my password
  blindly and press enter and the cursor freezes briefly as it does during
  a non-broken login. After a few seconds, I can press the volume up/down
  keys and I hear the volume sound. Pressing the app grid shortcut makes
  the cursor lag, just as it does when I disable the nvidia at the pcie
  link level and rendering works on i915. Backlight control also works on
  the login screen and once logged in. It's as if everything except the
  actual rendering to the screen is working.
  
  The minute I pass nouveau.modeset=0 in cmdline, or cut the power to the
  330m at the hardware level with outb 0x750, Wayland starts working
  again. The issue has something to do with GDM3's handling of a KMS-
  enabled nouveau GPU, whether it is headless or not (no difference with
  video=LVDS-2:d or not).
  
  To confirm my suspicions that it is not specific to the macbook pro
  line, this exact same issue (Xorg works wayland doesn't) also occurred
  on a desktop dual-gpu setup, with a GTX 760 (kepler) on nouveau tandem
  with a Haswell HD Graphics G3258-- with any combination of displays, all
  on the Intel, mixed on nvidia and intel, or all on nvidia, as long as
  both cards were modesetting, a black screen with cursor but blindly
  working gnome followed.
  
  This bug has existed since at least 19.04, if not earlier-- I replaced
  the nvidia gpu in that system with a Radeon 7870 when it ran that
  release due to this bug, as a matter of fact.

** Description changed:

  This bug should be able to be reproduced on any computer with both an
  nvidia (stock nouveau) and intel igpu (stock i915), booting to stock
  gdm3 (wayland by default). My main example is a MacBookPro6,2 with the
  infamous GT 330m on 20.04 with -proposed enabled and booting with the
  following grub manipulations to set gmux to the integrated LVDS:
  
  outb 0x710 2 - switch LVDS to intel
  outb 0x728 1 - switch internal DDC to intel
  outb 0x740 2 - switch displayport out to intel
  
  I am not using outb 0x750 0, so that the 330m remains powered on. It
  still works just fine-- the only thing broken is the LVDS connection to
  the internal panel. I disable it with video=LVDS-2:d.
  
  --> NOTE: This mod is only for the convenience of not having to deal
  with a phantom second screen once booted (both GPU's have the LVDS and
  edid of the internal screen hooked up). The computer boots fine and the
  bug reproduces exactly the same with or without it.
  
  I tested with all these modifications disabled, and this still occurred
  - it's not specific to my configuration. A user booting stock Ubuntu on
  this laptop, or as I discovered later, any nouveau + i915 hardware
  combination will run into this as well.
  
  Anyways, I'm keeping the 330m enabled to use DRI_PRIME to run
  applications on the 330m for good reason- it supports OpenGL 3.3 while
  HD Graphics (arrandale aka Ironlake) is the only HD Graphics iGPU stuck
  on OpenGL 2.1, thus otherwise vastly restricting the modern graphics
  workloads of the system.
  
  When explicitly booting with gdm3 WaylandEnable=false (login and desktop
  both xorg), everything works as expected - single screen driven by the
  i915's KMS, nouveau with DRI_PRIME working, returning NVA5 stats and
  functional with OpenGL 3 apps as well.
  
  On GDM3 wayland, however (the default-- which is why I think this bug is
  rather important), gdm3 starts to a black screen with cursor. The login
  screen and shell still seem to be running-- I can type my password
  blindly and press enter and the cursor freezes briefly as it does during
  a non-broken login. After a few seconds, I can press the volume up/down
  keys and I hear the volume sound. Pressing the app grid shortcut makes
  the cursor lag, just as it does when I disable the nvidia at the pcie
  link level and rendering works on i915. Backlight control also works on
  the login screen and once logged in. It's as if everything except the
  actual rendering to the screen is working.
  
  The minute I pass nouveau.modeset=0 in cmdline, or cut the power to the
  330m at the hardware level with outb 0x750, Wayland starts working
  again. The issue has something to do with GDM3's handling of a KMS-
  enabled nouveau GPU, whether it is headless or not (no difference with
  video=LVDS-2:d or not).
  
  To confirm my suspicions that it is not specific to the macbook pro
  line, this exact same issue (Xorg works wayland doesn't) also occurred
  on a desktop dual-gpu setup, with a GTX 760 (kepler) on nouveau tandem
  with a Haswell HD Graphics G3258-- with any combination of displays, all
  on the Intel, mixed on nvidia and intel, or all on nvidia, as long as
- both cards were modesetting, a black screen with cursor but blindly
- working gnome followed.
+ both cards were present and modesetting, a black screen with cursor but
+ blindly working gnome followed.
  
  This bug has existed since at least 19.04, if not earlier-- I replaced
  the nvidia gpu in that system with a Radeon 7870 when it ran that
  release due to this bug, as a matter of fact.

** Tags added: amd64 disco eoan focal

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https://bugs.launchpad.net/bugs/1873541

Title:
  black screen with cursor on dual nouveau + i915

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