Regression in drm: drm/fbdev doesn't initialize if set to triple buffer
mohammad.rasim96 at gmail.com
Sat Sep 8 09:48:39 PDT 2018
I've an issue where the drm_meson driver doesn't work, it used to work
in earlier 4.18 release and stopped working after about 4.18-rc3.
My board is videostrong k2 pro (S905 SoC), I use the meson-gxbb-p201
on the latest 4.19 tree the board boots fine but the drm driver doesn't
work, and spits the following error in dmesg
[ 2.489825] meson-drm d0100000.vpu: Queued 3 outputs on vpu
[ 2.494685] meson-drm d0100000.vpu: Failed to create d0100000.vpu
[ 2.502051] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
[ 2.508668] [drm] No driver support for vblank timestamp query.
[ 2.573756] meson-drm d0100000.vpu: bound c883a000.hdmi-tx (ops
[ 2.695917] meson-drm d0100000.vpu: [drm:drm_fb_helper_fbdev_setup]
*ERROR* Failed to set fbdev configuration
[ 2.700310] meson-drm d0100000.vpu: master bind failed: -22
[ 2.705747] meson-drm: probe of d0100000.vpu failed with error -22
Digging deeper into the problem revealed that the problem is related to
the CONFIG_DRM_FBDEV_OVERALLOC option, If I set it to 100 or 200 it
works fine and the drm driver works ( or by passing
drm_kms_helper.drm_fbdev_overalloc=200 in the bootargs). The problem
reappears when setting it to 300.
Bisecting shows that the first bad commit that introduced this
regression is this: 244007ecb6bb94fa4e9b9a969fa86f2ad86ec543
Another problem that I face and might be related is that the sometimes
the boot get stuck on the following lines:
[ 2.501539] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
[ 2.508158] [drm] No driver support for vblank timestamp query.
This problem is random and can't always reproduced, sometimes it takes a
few reboots to get the board to boot pass those lines.
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