With Mesa 21 evdi and udl displays are black

This was noticed by DisplayLink evdi driver users here: https://github.com/DisplayLink/evdi/issues/279

Issue is reproducible on Pop!_OS 20.10

In verbose drm dmesg logs there is following error:

[drm:drm_ioctl [drm]] comm="Xorg" pid=1283, dev=0xe201, auth=1, DRM_IOCTL_MODE_ADDFB
[drm:framebuffer_check [drm]] no buffer object handle for plane 0
[drm:drm_ioctl [drm]] comm="Xorg", pid=1283, ret=-22

And in Xorg.log

[    21.874] (II) modeset(0): Modeline "1920x1080"x0.0  152.84  1920 2000 2060 2250  1080 1086 1094 1132 -hsync -vsync (67.9 kHz eP)
[    22.081] failed to add fb -22

After investigation and some debugging we have found out that Mesa 21.0.0 is trigering that issue.

I have noticed that there is missing DRM_IOCTL_PRIME_FD_TO_HANDLE ioctl. This lead me to the difference in modesetting msSetSharedPixmapBacking function. In faulty case, stack trace looks like this:

#0  glamor_egl_create_textured_pixmap_from_gbm_bo
    (pixmap=0x55b1971faf80, bo=0x55b1970ebcb0, used_modifiers=0)
    at ../../../../../../glamor/glamor_egl.c:243
#1  0x00007f0a052ae40c in glamor_back_pixmap_from_fd
    (pixmap=0x55b1971faf80, fd=68, width=1920, height=1080, stride=7680, depth=24 '\030', bpp=32 ' ')
    at ../../../../../../glamor/glamor_egl.c:512
#2  0x00007f0a052fac1c in msSetSharedPixmapBacking (ppix=0x55b1971faf80, fd_handle=0x44)
    at ../../../../../../../hw/xfree86/drivers/modesetting/driver.c:1460
#3  0x000055b1955745a3 in PixmapShareToSlave (pixmap=0x55b197110c70, slave=0x55b1970e25b0)
    at ../../../../dix/pixmap.c:167
#4  0x000055b19565ec3e in rrCreateSharedPixmap
    (crtc=0x55b197238780, master=0x55b195b20a70, width=1920, height=1080, depth=24, x=1920, y=0, rotation=1) at ../../../../randr/rrcrtc.c:441
#5  0x000055b19565ef6b in rrSetupPixmapSharing
    (crtc=0x55b197238780, width=1920, height=1080, x=1920, y=0, rotation=1, sync=1, numOutputs=1, outputs=0x55b195d3ea10) at ../../../../randr/rrcrtc.c:538
#6  0x000055b19565f9d2 in RRCrtcSet
    (crtc=0x55b197238780, mode=0x55b19722f050, x=1920, y=0, rotation=1, numOutputs=1, outputs=0x55b195d3ea10) at ../../../../randr/rrcrtc.c:773
#7  0x000055b19566160c in ProcRRSetCrtcConfig (client=0x55b1964ed2e0) at ../../../../randr/rrcrtc.c:1418
#8  0x000055b19565d8a6 in ProcRRDispatch (client=0x55b1964ed2e0) at ../../../../randr/randr.c:717
#9  0x000055b195541070 in Dispatch () at ../../../../dix/dispatch.c:479
#10 0x000055b1955505a9 in dix_main (argc=15, argv=0x7ffed9ea4a98, envp=0x7ffed9ea4b18)
    at ../../../../dix/main.c:276
#11 0x000055b1955309a5 in main (argc=15, argv=0x7ffed9ea4a98, envp=0x7ffed9ea4b18)
    at ../../../../dix/stubmain.c:34

In working case(when Mesa 20.3.X was installed):

#0  0x00007fd94cd0e3d0 in drmPrimeFDToHandle () at /lib/x86_64-linux-gnu/libdrm.so.2
#1  0x00007fd94bc824f5 in dumb_get_bo_from_fd (fd=62, handle=64, pitch=7680, size=8294400) at
../../../../../../../hw/xfree86/drivers/modesetting/dumb_bo.c:130
#2  0x00007fd94bc7a78e in drmmode_SetSlaveBO (ppix=0x55906c387f80, drmmode=0x55906c2c4e38, fd_handle=64, pitch=7680,
size=8294400) at ../../../../../../../hw/xfree86/drivers/modesetting/drmmode_display.c:1070
#3  0x00007fd94bc76c61 in msSetSharedPixmapBacking (ppix=0x55906c387f80, fd_handle=0x40) at
../../../../../../../hw/xfree86/drivers/modesetting/driver.c:1467
#4  0x000055906a2e45a3 in PixmapShareToSlave (pixmap=0x55906c5e69b0, slave=0x55906c2b9590) at
../../../../dix/pixmap.c:167
#5  0x000055906a3cec3e in rrCreateSharedPixmap (crtc=0x55906c2b9ad0, master=0x55906b488a70, width=1920, height=1080,
depth=24, x=1920, y=0, rotation=1) at ../../../../randr/rrcrtc.c:441
#6  0x000055906a3cef6b in rrSetupPixmapSharing (crtc=0x55906c2b9ad0, width=1920, height=1080, x=1920, y=0, rotation=1,
sync=1, numOutputs=1, outputs=0x55906c3bfcf0) at ../../../../randr/rrcrtc.c:538
#7  0x000055906a3cf9d2 in RRCrtcSet (crtc=0x55906c2b9ad0, mode=0x55906c5e25d0, x=1920, y=0, rotation=1, numOutputs=1,
outputs=0x55906c3bfcf0) at ../../../../randr/rrcrtc.c:773
#8  0x000055906a3d160c in ProcRRSetCrtcConfig (client=0x55906c04f400) at ../../../../randr/rrcrtc.c:1418
#9  0x000055906a3cd8a6 in ProcRRDispatch (client=0x55906c04f400) at ../../../../randr/randr.c:717
#10 0x000055906a2b1070 in Dispatch () at ../../../../dix/dispatch.c:479
#11 0x000055906a2c05a9 in dix_main (argc=15, argv=0x7ffd6dd18d38, envp=0x7ffd6dd18db8) at ../../../../dix/main.c:276
#12 0x000055906a2a09a5 in main (argc=15, argv=0x7ffd6dd18d38, envp=0x7ffd6dd18db8) at ../../../../dix/stubmain.c:34

When you will go deeper glamor_egl_create_textured_pixmap_from_gbm_bo was referencing zink gallium driver. I have not found what could be wrong there, maybe we could fix that.

Nevertheless I have noticed one more thing. Until Mesa 20.X glamor_egl_init was failing on llvmpipe renderer check (for evdi/udl displays) which was leading to disabled glamor.

As a side-effect modesetting reverse_prime_offload_mode mode was always disabled. Now with new Mesa 21.0 GL_RENDERER for evdi display is "zink (Intel(R) HD Graphics 5500 (BDW GT2))" This is causing glamor to init and enable reverse_prime_offload_mode.

MR !681 (merged) is fixing this issue by disabling reverse_prime_offload_mode.

mentioned in merge request !681 (merged)

Seems to be fixed in !681 (merged).

Thanks for merging that in.

I want to merge that fix to server-1.20-branch. Shall I create separate MR?

Shall I create separate MR?

Yes. It will not be me who can approve that MR though.

Yes. It will not be me who can approve that MR though.

Ok, Who is capable to do that?

Here is MR with cherry-pick !683 (merged)

Ok, Who is capable to do that?

@mattst88 is the release manager for the 1.20.x releases.

To be precise, I can approve and already did that, the code looks good. But Matt will be the one who's merging and then managing subsequent releases.

closed

mentioned in merge request !683 (merged)