linux-kernel - /sys/kernel/debug/vgaswitcheroo directory missing

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Date: Wed, 8 May 2024 09:02:02 +0100
From: Chris Clayton <chris2553@...glemail.com>
To: LKML <linux-kernel@...r.kernel.org>, dri-devel@...ts.freedesktop.org
Subject: /sys/kernel/debug/vgaswitcheroo directory missing

Hi,

I'm running the latest development kernel - 6.9.0-rc7+ (HEAD is dccb07f2914cdab2ac3a5b6c98406f765acab803.)

As I say in $SUBJECT, the directory /sys/kernel/debug/vgaswitcheroo is missing in this release. Perhaps more importantly
unless it is configured to simply blank the screen, when xscreensaver kicks in an error message flashes rapidly on and
off complaining that no GL graphics are available. Moreover, if I start scribus from qterminal, I see the message
"Inconsistent value (1) for DRI_PRIME. Should be < 1 (GPU devices count). Using: 0".

This same userspace works fine with kernels 6.6.30 and 6.8.9

lsmod shows that the nouveau module is loaded and lsof shows that libdrm_nouveau is loaded for Xorg and a few desktop
applications. However, inspecting the nouveau-related output from dmesg reveals:

[Wed May  8 08:20:07 2024] nouveau: detected PR support, will not use DSM
[Wed May  8 08:20:07 2024] nouveau 0000:01:00.0: enabling device (0006 -> 0007)
[Wed May  8 08:20:07 2024] nouveau 0000:01:00.0: NVIDIA TU117 (167000a1)
[Wed May  8 08:20:07 2024] nouveau 0000:01:00.0: bios: version 90.17.42.00.36
[Wed May  8 08:20:07 2024] nouveau 0000:01:00.0: pmu: firmware unavailable
[Wed May  8 08:20:07 2024] nouveau 0000:01:00.0: fb: 4096 MiB GDDR6
[Wed May  8 08:20:07 2024] nouveau 0000:01:00.0: sec2(acr): mbox 00000007 00000000
[Wed May  8 08:20:07 2024] nouveau 0000:01:00.0: sec2(acr):AHESASC: boot failed: -5
[Wed May  8 08:20:07 2024] nouveau 0000:01:00.0: acr: init failed, -5
[Wed May  8 08:20:07 2024] nouveau 0000:01:00.0: init failed with -5
[Wed May  8 08:20:07 2024] nouveau: DRM-master:00000000:00000080: init failed with -5
[Wed May  8 08:20:07 2024] nouveau 0000:01:00.0: DRM-master: Device allocation failed: -5
[Wed May  8 08:20:07 2024] nouveau 0000:01:00.0: probe with driver nouveau failed with error -5

With kernel 6.8.9 the equivalent output is :

Wed May  8 08:51:07 2024] nouveau: detected PR support, will not use DSM
[Wed May  8 08:51:07 2024] nouveau 0000:01:00.0: enabling device (0006 -> 0007)
[Wed May  8 08:51:07 2024] nouveau 0000:01:00.0: NVIDIA TU117 (167000a1)
[Wed May  8 08:51:07 2024] nouveau 0000:01:00.0: bios: version 90.17.42.00.36
[Wed May  8 08:51:07 2024] nouveau 0000:01:00.0: pmu: firmware unavailable
[Wed May  8 08:51:07 2024] nouveau 0000:01:00.0: fb: 4096 MiB GDDR6
[Wed May  8 08:51:07 2024] nouveau 0000:01:00.0: DRM: VRAM: 4096 MiB
[Wed May  8 08:51:07 2024] nouveau 0000:01:00.0: DRM: GART: 536870912 MiB
[Wed May  8 08:51:07 2024] nouveau 0000:01:00.0: DRM: BIT table 'A' not found
[Wed May  8 08:51:07 2024] nouveau 0000:01:00.0: DRM: BIT table 'L' not found
[Wed May  8 08:51:07 2024] nouveau 0000:01:00.0: DRM: TMDS table version 2.0
[Wed May  8 08:51:07 2024] nouveau 0000:01:00.0: DRM: MM: using COPY for buffer copies
[Wed May  8 08:51:07 2024] [drm] Initialized nouveau 1.4.0 20120801 for 0000:01:00.0 on minor 1
[Wed May  8 08:51:07 2024] nouveau 0000:01:00.0: [drm] No compatible format found
[Wed May  8 08:51:07 2024] nouveau 0000:01:00.0: [drm] Cannot find any crtc or sizes
[Wed May  8 08:51:07 2024] nouveau 0000:01:00.0: DRM: Disabling PCI power management to avoid bug

I've attached the complete dmesg output from 6.9.8-rc7+.

Please cc me on any reply as I'm not subscribed.

Chris


View attachment "dmesg-switcheroo-missing.txt" of type "text/plain" (68206 bytes)