On 12/01/2016 06:47 PM, Ralf Ramsauer wrote:
Hi Stephen,

On 12/01/2016 05:04 PM, Stephen Warren wrote:
On 12/01/2016 07:15 AM, Ralf Ramsauer wrote:

I observed that touching MMIO regions of Tegra devices with its
corresponding clock gate deactivated immediately freezes the whole
system. No kernel panic, nothing.

I tested this behavior with a small kernel module, find it attached. A
few seconds after loading this module, the whole device freezes. Tested
this on a TK1 and TX1.

Unfortunately, this is indeed the way the HW works.
That's no good news :(

Do you know if this applies to the whole Tegra architecture or only to
some boards?

It does apply to the whole architecture for all revisions pre-Tegra186 (which is newer than Tegra210 despite the number).

- Mikko

What is the actual expected behavior on ARM(64) when touching ungated
MMIO regions? Is it specified somewhere?

I don't believe the ARM architecture specifies behaviour in this case,
or if it does, defines it as implementation defined, which means that
pretty much any behaviour is valid.
I tested the same scenario on another ARM64 board (LeMaker HiKey), which
did (fortunately) not freeze.

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