twobikes22
Posts: 3
Joined: Sat Jul 06, 2019 2:52 am

Pi 4, 4GB RAM, not booting, CMA: failed to reserve 256 MiB mib.

Sat Jul 06, 2019 3:37 am

New Pi 4, booted several times using buster full OK. Then in Raspberry Pi Config menu re allocated memory for GPU from 64 to 1024, dialog box returned 896 i think, left it at that also set hdmi port 0 to 60Hz, then rebooted.

Flash screen, 4 raspberry's, and following error messages:

[ 0.000000] cma: Failed to reserve 256 MiB
[ 0.220610] brcm-pcie fd500000.pcie: dmabounce: could not allocate 33554432 byte DMA pool
[ 0.220696] brcm-pcie fd500000.pcie: could not init bounce buffers: -12
[ 0.749793] [vc_sm_connected init]: failed to initialise CMA heap

Screen blanks out and nothing, also no USB port working or have power. No USB power worries me!

Any ideas? Have I faulty memory chip?

twobikes22
Posts: 3
Joined: Sat Jul 06, 2019 2:52 am

Re: Pi 4, 4GB RAM, not booting, CMA: failed to reserve 256 MiB mib.

Sat Jul 06, 2019 6:14 am

Sorted it out myself. Fortunately had enabled ssh, so ssh into pi, and edited /boot/config.txt, had the line gpu_mem=896, changed it to gpu_mem=256, saved and rebooted.

This fixed the usb ports and booted into gui. Begs the question why did it return 896, when i entered 1024 then corrupt the boot and usb ports on reboot?

What is the highest gpu_mem? 512, I tried 1024 for gui to insert 896. But does higher mem allocation help video performance? more play and pain will tell what the limits.

kflmiami420
Posts: 61
Joined: Thu Mar 21, 2019 6:54 pm

Re: Pi 4, 4GB RAM, not booting, CMA: failed to reserve 256 MiB mib.

Sat Jul 06, 2019 8:46 am

try buster with desktop instead

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rpdom
Posts: 19035
Joined: Sun May 06, 2012 5:17 am
Location: Chelmsford, Essex, UK

Re: Pi 4, 4GB RAM, not booting, CMA: failed to reserve 256 MiB mib.

Sat Jul 06, 2019 11:22 am

No point in putting GPU memory over 256MB. The new VC6 uses CMA to split memory between CPUS and GPU as required.

Even 256MB is possibly excessive.
Unreadable squiggle

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bensimmo
Posts: 5439
Joined: Sun Dec 28, 2014 3:02 pm
Location: East Yorkshire

Re: Pi 4, 4GB RAM, not booting, CMA: failed to reserve 256 MiB mib.

Sat Jul 06, 2019 12:33 pm

Less and less will need the GPU allocation set aside.
Leave it at default unless it complains.

twobikes22
Posts: 3
Joined: Sat Jul 06, 2019 2:52 am

Re: Pi 4, 4GB RAM, not booting, CMA: failed to reserve 256 MiB mib.

Sat Jul 06, 2019 9:26 pm

Thank you for the replies.

Learned that CMA stands for Contiguous Memory Allocation, this from a neat web site www.allacronyms.com, which will be my 1st place of call when I think what does ***** stand for? Yeah and back in the days I once thought LOL was Lots of Love.

Also learned that allocating more than 64 is not really going to help video performance, but hey I have got 4GB, so I think I will compromise at 128.

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bensimmo
Posts: 5439
Joined: Sun Dec 28, 2014 3:02 pm
Location: East Yorkshire

Re: Pi 4, 4GB RAM, not booting, CMA: failed to reserve 256 MiB mib.

Sun Jul 07, 2019 8:39 am

If you didn't find it
https://www.raspberrypi.org/forums/view ... 7&start=50
So we'll see how they get on with the big changes.
(And there is another roost somewhere)

Towelie
Posts: 1
Joined: Fri Jul 26, 2019 11:49 am

Re: Pi 4, 4GB RAM, not booting, CMA: failed to reserve 256 MiB mib.

Fri Jul 26, 2019 11:54 am

I am having the same issue. The difference is the software I run seems to check for available video memory and won't run if it is set to low.

The max I can seem to set it at is 512. Does anyone know of any way around this?

scarlet_man
Posts: 1
Joined: Fri Sep 27, 2019 5:27 pm

Re: Pi 4, 4GB RAM, not booting, CMA: failed to reserve 256 MiB mib.

Fri Sep 27, 2019 5:32 pm

Huge thanks to twobikes22 - this saved me.

Had the same problem, tried setting video memory to 1024 just - well - just for something to do :D

Next day found blank display on boot up...

Followed a slightly different process, not using SSH.

I happened to have another SD card with Raspbian on which came with the PI4 bundle, which I'd kept when I upgraded to 32GB. Was able to boot from this, then connect the usual SD card into a USB adaptor. Browsed to the SD and reset the line of config.txt as advised by twobikes22.

10 minute fix. Many thanks.

simonliu
Posts: 2
Joined: Tue Mar 17, 2020 1:43 pm

Re: Pi 4, 4GB RAM, not booting, CMA: failed to reserve 256 MiB mib.

Sat Apr 18, 2020 9:38 am

In my Pi 4b 2GB RAM, I changed the gpu_mem=192 to gpu_mem =256, and it is working fine.

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