coherent_pool setting to 1M or 6M on wandboard solo

[viks]

Hi all,

I am trying to use the virtual framebuffer driver from "https://community.freescale.com/message/422194#422194". However

I am getting following error when i try to insert the virtual_fb.ko in Linux 3.10.17 on wandboard.

 

ERROR: 256 KiB atomic DMA coherent pool is too small!

Please increase it with coherent_pool= kernel parameter!

(NULL device *): Unable to allocate framebuffer memory

detected fb_set_par error, error code: -12

(NULL device *): Unable to allocate framebuffer memory

detected fb_set_par error, error code: -12

(NULL device *): Unable to allocate framebuffer memory

detected fb_set_par error, error code: -12

 

How to set coherent_pool= for wandboard which is using uboot? I tried setenv bootargs coherent_pool=6M, but no luck.

Regards,

Vikash

[Alexander Holler]

If you compile your own kernel, the easiest way might be to put the
cmdline into the kernel and let the kernel ignore the one from u-boot
(CMDLINE_FORCE). You might use cat /proc/cmdline as a template.

Another option is to modify u-boot to use uEnv.txt, I've explained such
a few mails before. Or you can build an old u-boot-script (I think the
wandboard u-boot-config looks for boot.cmd) and use that instead of
uEnv.txt.

Regards,

Alexander Holler

[John Weber]

What is your bootargs after you set coherent_pool? Can you try (with a fresh
image) something like this?

setenv bootargs ${bootargs} coherent_pool=6M

This concatenates the coherent_pool string with the existing bootargs string,
which preserves any existing kernel parameter assignments.

However... not sure how the image you're using assigns bootargs in the first
place. A lot of times this is set with other u-boot macros depending on the
boot configuration.

For example, with u-boot-fslc (from mainline Yocto), if booting from MMC,
bootargs is built using other environment variables (mmcargs), so I would try this:

setenv mmcargs ${mmcargs} coherent_pool=6M

[Vikas Patil]

Thanks John and Holler.

I used the following command set the coherent_pool on wandboard after looking at the printenv output

setenv mmcargs "setenv bootargs console=${console},${baudrate} root=${mmcroot} coherent_pool=6M; run videoargs"

Thanks & Regards,

Vikash

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