#1138060 riscv64: please enable contiguous memory allocator (CMA) support, needed for HDMI displays

Package:
src:linux
Source:
src:linux
Submitter:
Dominique Belhachemi
Date:
2026-05-29 04:33:03 UTC
Severity:
normal
#1138060#5
Date:
2026-05-27 17:34:53 UTC
From:
To:
Dear maintainer,

Please enable CMA on riscv64.

  CONFIG_CMA=y
  CONFIG_DMA_CMA=y

This is required on SBCs (e.g. with JH7110 or TH1520) to allocate the framebuffer for normal HD displays at 1920x1080 or higher.
Without this, the display falls back to something like 1024×768 and typically stays black.

I am currently using `cma=128M` on the cmdline which works fine at 1920x1080.

Best
-Dominique
#1138060#10
Date:
2026-05-27 19:54:06 UTC
From:
To:
Hi Dominique,

Both options got enabled starting with linux 7.1~rc3-1~exp1, currently
available in experimental. Could you please confirm that it works for
your use case?

Thanks
Aurelien
#1138060#15
Date:
2026-05-28 04:47:35 UTC
From:
To:
Hi Aurelien,
Thank you, yes it works. I just tested it with 7.1~rc4-1~exp1 on a
VisionFive 2 SBC with additional HDMI patches.
Debian's kernel config uses
    CONFIG_CMA_SIZE_MBYTES=64
which is good enough for two 1920x1080 framebuffers.
For 4K I could simply specify cma=128M on the cmdline.

Best
-Dominique
#1138060#20
Date:
2026-05-28 21:38:59 UTC
From:
To:
Hi,

Thanks for the confirmation. I am therefore closing this bug with that
version.

Regards
Aurelien
#1138060#25
Date:
2026-05-28 21:38:59 UTC
From:
To:
Hi,

Thanks for the confirmation. I am therefore closing this bug with that
version.

Regards
Aurelien