[regression] TI LT kernel only sees 638MB of RAM out of 1GB on the PandaBoard with device tree

you seem to be missing CONFIG_HIGHMEM in your kernel. can you check this ?

This is not "my" kernel, this is the stock kernel that was installed when creating the linaro image by following the instructions on the page mentioned above. How would I check that?

It's the same old bug that only happens when device tree is enabled :-(

After removing device tree support, I'm able to see 1gb.

Seems this is similar as bug 707047.

But this time seems the u-boot env is correct:

setenv initrd_high "0xffffffff"
setenv fdt_high "0xffffffff"
setenv bootcmd "fatload mmc 0:1 0x80200000 uImage; fatload mmc 0:1 0x81600000 uInitrd; fatload mmc 0:1 0x815f0000 board.dtb; bootm 0x80200000 0x81600000 0x815f0000"
setenv bootargs "console=tty0 console=ttyO2,115200n8 root=UUID=abb086b0-d01c-412a-bf3a-07823833f3fb rootwait ro earlyprintk fixrtc nocompcache vram=48M omapfb.vram=0:24M mem=456M@0x80000000 mem=512M@0xA0000000"

I will ping Dave Long about this. He looked at # 707047 so he may have something to say about this one. He should be back tomorrow since it is American Thanksgiving today.

Dave, I notice the dts for Panda on tilt-3.1 has

/memreserve/ 0x9D000000 0x03000000; /* Frame buffer */
/memreserve/ 0xB0000000 0x10000000; /* Top 256MB is unaccessable */

Did we not remove the second line at some point?

On 3.2-rc2 the dts has totally changed and doesn't define any memory reservations I can see.

I fixed this once before ("display" below should read "disable"):

commit 3d3828845d9c4069a5d86c4fd21b2ec8de4176f1
Author: David A. Long <email address hidden>
Date: Wed Jul 27 14:23:07 2011 -0400

    Remove display of last 1/4GB of Panda SDRAM (requires latest u-boot and l-m-c).

I do not know why this was undone. The line in omap4-panda.dts reading:

/memreserve/ 0xB0000000 0x10000000; /* Top 256MB is unaccessable */

should (once again) be deleted.

Another place this can get broken is the config file. It does not look like that is the problem this time, but it is worth doing:

zcat /proc/config.gz | grep HIGHMEM

to verify that no one has introduced a configuration regression. HIGHMEM must be set for the top 1/4GB of memory to be useable.

Dave: Are you planning on making the change in #7? if os, can you please assign the bug to your self and mark it fix committed when the fix is checked in.

We were simply missing Dave's patch from tilt-3.0 in tilt-3.1. I've added this and regenerated tilt-linux-linaro-3.1 from it that Ricardo uses, so "fix committed". Not added to tracking since dts no longer has these lines there.

HIGHMEM is enabled at our latest kernel package. Guess this will be fixed once John rebases our packaging with the latest tilt-linux-linaro-3.1.

Thanks for looking for the fix.

With latest kernel (linux-image-3.1.0-1402-linaro-lt-omap 3.1.0-1402.5rsalveti1) it seems to be working again. I'm now able to see 894MB.

[ 0.000000] Memory: 456MB 463MB = 919MB total
[ 0.000000] Memory: 913824k/913824k available, 77408k reserved, 211968K highmem