Please enable CONFIG_DMA_CMA=y on arm64

[Adam Smith]

Using the generic arm64 kernel on my raspberry pi 3 it seems impossible to use any apps that require 3D graphics. The X session crashes and a reboot is needed to make it bootable again.

Inspecting dmesg, there are a lot of "failed to allocate CMA" messages. Adding cma=256M to the kernel command line has no effect. Dropping resolution allows firefox to start, but 3D apps still fail.

I believe the vc4 driver needs CONFIG_DMA_CMA=y, which currently the generic kernel does not set. The raspi2 kernel has this and 3D graphics works.

[CodeExecution (code-exec)]

Same issue here. Apps like Chromium freeze the Pi, and the display output also goes off screen.

[Seth Forshee (sforshee)]

This option has been turned on for arm64 in the 5.0 kernel tree that will be used for disco.

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux - 5.0.0-7.8

---------------
linux (5.0.0-7.8) disco; urgency=medium

  * linux: 5.0.0-7.8 -proposed tracker (LP: #1818519)

  * Packaging resync (LP: #1786013)
    - [Packaging] update helper scripts

  * unnecessary request_queue freeze (LP: #1815733)
    - block: avoid setting nr_requests to current value
    - block: avoid setting none scheduler if it's already none

  * Miscellaneous Ubuntu changes
    - SAUCE: selftests: net: Don't fail test_vxlan_under_vrf on xfail
    - update dkms package versions

  [ Upstream Kernel Changes ]

  * Rebase to v5.0

 -- Seth Forshee <email address hidden> Mon, 04 Mar 2019 08:46:10 -0600

[dann frazier (dannf)]

Just to add a tag back, this fix is causing regressions on some server platforms in bug 1823753

[satmandu (satadru-umich)]

On the flip side, I am able to use dtoverlay=vc4-kms-v3d,cma-256 to boot my 3B+ on the disco kernel, which appears to allow me to use hardware accelerated decoding on the RPI.