Re: "ARM: multi_v7_defconfig: Enable shmobile platforms" breaks Tegra20 multi_v7_defconfig boot

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On 04/01/2015 11:14 AM, Stephen Warren wrote:
On 03/26/2015 12:57 PM, Stephen Warren wrote:
On 03/26/2015 12:35 PM, Paul Walmsley wrote:
On Wed, 25 Mar 2015, Stephen Warren wrote:

On 03/25/2015 04:00 PM, Paul Walmsley wrote:
On Wed, 25 Mar 2015, Tyler Baker wrote:
On 25 March 2015 at 11:03, Paul Walmsley <paul@xxxxxxxxx> wrote:
Looks like commit 4a3a6f86693922b29cf829c63f652b057f14619e ("ARM:
multi_v7_defconfig: Enable shmobile platforms") breaks Tegra20
multi_v7_defconfig boot.
...
Can you try to shift your kernel load address around a bit? From
experience with the boards from kernelci.org we find that as the multi
v7 kernel size increases they can clobber memory when they get
decompressed.

Thanks, that was it:

http://nvt.pwsan.com/pub/pwalmsley-tester/testlogs/test_20150325144058_6af714b069dc278d5d8e1b7afc13568f71d9aba8/20150325144058/boot/tegra20-trimslice/tegra20-trimslice/multi_v7_defconfig_log.txt
...
Interesting. Do the values in U-Boot's default environment work
correctly

No idea, I haven't tried.  (The load addresses I used are observable in
the boot logs above.)

Sure. I was hoping you'd try it out since you already had the setup to
repro the issue.

It'd be good if your test-bed used the built-in U-Boot variables too, so
we're testing them.

I've reproduced the original problem, and then validated that using the addresses from U-Boot's default environment (at least with a ToT U-Boot that I just built) does indeed solve it.

I'd like to re-iterate that the test bed should be using the values from U-Boot's environment rather than making up its own. That way:

* The value the test bed uses for the kernel load address likely overlaps where the kernel decompressor writes to for even slightly large kernels. This means the decompressor must move itself before decompressing. IIUC, there's zero guarantee that moving the decompressor won't overwrite the DTB, since IIUC the decompressor uses zero knowledge of the DTB location. In other words, if the compressed kernel is loaded somewhere that's likely to require it to move itself, there's a real risk of the exact same problem cropping up again in the future if the kernel happens to overwrite the DTB during relocation.

* The values are part of every Tegra U-Boot port (and hopefully for other SoCs too given any distro using boot.scr with config_distro_bootcmd.h will expect the variables to exist), so for future (Tegra) chips you won't have to adjust the test bed if RAM layout changes.

* Those values get testing, so we'll find out if the ever don't work. We get more test coverage.

Sounds reasonable, I'll try to get to this at some point soon.

BTW, it might be worth changing U-boot CONFIG_LOADADDR to point to the value you define for kernel_addr_r. That would reinforce to folks who aren't using the U-boot scripts that they should use that address for loading their kernel.


- Paul


- Paul
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