[U-Boot] [PATCH] ARM: tegra: only enable SCU on Tegra20

[Tom Warren]

Sorry, my BW is being used up by internal projects. I'll pull it down, apply/build/test in u-boot-tegra/next, and then I can send a PR to Albert if you think it needs to move higher up right away.

Tom

> -----Original Message-----
> From: Stephen Warren [mailto:swarren at wwwdotorg.org]
> Sent: Tuesday, June 04, 2013 12:34 PM
> To: Tom Warren
> Cc: u-boot at lists.denx.de; Simon Glass; Stephen Warren
> Subject: Re: [U-Boot] [PATCH] ARM: tegra: only enable SCU on Tegra20
> 
> On 05/23/2013 04:26 PM, Stephen Warren wrote:
> > From: Tom Warren <twarren at nvidia.com>
> >
> > The non-SPL build of U-Boot on Tegra only runs on a single CPU, and
> > hence there is no need to enable the SCU when running U-Boot. If an
> > SMP OS is booted, and it needs the SCU enabled, it will enable the SCU
> > itself. U-Boot doing so is redundant.
> >
> > The one exception is Tegra20, where an enabled SCU is required for
> > some aspects of PCIe to work correctly.
> >
> > Some Tegra SoCs contain CPUs without a software-controlled SCU. In
> > this case, attempting to turn it on actively causes problems. This is
> > the case for Tegra114. For example, when running Linux, the first (or
> > at least some very early) user-space process will trigger the
> > following kernel
> > message:
> >
> > Unhandled fault: imprecise external abort (0x406) at 0x00000000
> >
> > This is typically accompanied by that process receving a fatal signal,
> > and exiting. Since this process is usually pid 1, this causes total
> > system boot failure.
> 
> Tom, is this patch OK? It's a rather critical bug-fix for Tegra114, so I'd like to
> make sure it gets into the upcoming release. Thanks.
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