[U-Boot] [PATCH v2 1/2] configs: mx6_common: Restrict CONFIG_ARM_ERRATA_742230 for multi-core

[Shawn Guo]

On Thu, Jan 09, 2014 at 03:50:06AM +0000, Hui.Liu at freescale.com wrote:
> The commit log really get me confused, why we need enable one ERRATA which should not be applied?

It's been enabled as a workaround for the reboot issue we were seeing
before.  But I get reminded that the workaround may not be needed
anymore, because of the recent kernel commit 87a84b69 (ARM: imx: replace
imx6q_restart() with mxc_restart()).  The real change is that we do not
call of_iomap() in restart hook now.

Fabio,

Can you give it a test to see if reboot works fine with v3.13-rc kernel
with dropping the ERRATA from u-boot?  If reboot works and nothing else
breaks, we may want to just remove the ERRATA selection from u-boot.

> This will make customer confused at all. We need find the real root-cause for it other than hack it
> Otherwise, you will get more and more problems sooner or later...

If you go through the thread [1], you will see that the root-cause had
pretty much been identified, - issuing dmb instructions in a tight loop
causes the problem.  But people did not reach a conclusion how it should
be fixed.

> 
> If you looking at the link in [1], it said, this issue only affected with v6+v7 one zImage kernel,
> And not exist with v7 only kernel, which means something should be wrong with v6+v7 one zImage kernel.

Again, if you go though the discussion, you will find the issue could be
easily made up on v7 only kernel.

Shawn

[1] http://thread.gmane.org/gmane.linux.ports.arm.kernel/180876