On Thu, May 07, 2015 at 10:29:03AM +0100, Bintian wrote:

On 2015/5/7 17:02, Will Deacon wrote:

quoted

On Tue, May 05, 2015 at 01:06:34PM +0100, Bintian Wang wrote:

quoted

Hi6220 is one mobile solution of Hisilicon, this patchset contains
initial support for Hi6220 SoC and HiKey development board, which
supports octal ARM Cortex A53 cores. Initial support is minimal and
includes just the arch configuration, clock driver, device tree
configuration.

PSCI is enabled in device tree and there is no problem to boot all the
octal cores, and the CPU hotplug is also working now, you can download
and compile the latest firmware based on the following link to run this
patch set:
https://github.com/96boards/documentation/wiki/UEFI

Changes v4:
* Rebase to kernel 4.1-rc1
* Delete "arm,cortex-a15-gic" from the gic node in dts

I gave these patches a go on top of -rc2 using the ATF and UEFI you link to
above.

The good news is that the thing booted and all the cores entered at EL2.
Thanks!

Really thank you very much for testing this patch set.

Feel free to add my tested-by if you like.

quoted

The bad news is that running hackbench quickly got the *heatsink*
temperature to 73 degress C and rising (measured with an infrared
thermometer).

This patch set is just for booting the small system, if you want to
test the temperature, I think you should using the HiKey released
version (https://www.96boards.org/).

I'm not really interested in the temperature numbers, but I am interested
in the board not melting and potentially setting fire to my desk.

This patch is just for the small system, and not include those drivers
for adjusting the CPU frequency, thermal control and so on. After this
patch is merged, all those drivers will be submitted later.

Should those drivers *really* exist only in the kernel? What happens if
the kernel panics for some other reason? You'll basically have 8 spinning
cores and no sensible way to handle the thermal interrupt.

Shouldn't there be something in the secure firmware as a last resort?

quoted

So my question is, does this SoC have an automatic thermal cut out? Whilst
I'm all for merging enabling code into the kernel, if it really relies on
the kernel to stop it from catching fire, maybe it's not a great idea
putting these patches into people's hands just yet.

Hikey is a low cost board, I think it doesn't have an automatic thermal
cut out; I always use HiKey to test my patch, in the normal case, 
temperature is not a problem.

I don't see why the cost has anything to do with this issue; any money I
save on the board will quickly be re-invested in my increased insurance
premium.

All I think we need is for secure software to keep an eye on the temperature
and hit the power controller if it goes over some `fatal' threshold.
Ideally, you'd be able to use a secure interrupt for this, but I suspect
that you don't have the right hardware features for that (please correct me
if I'm wrong). An alternative would be to hang something off a secure timer
and get the firmware to check the board temperature on some low-frequency
periodic tick.

Will