On Fri, Feb 27, 2015 at 01:07:42PM +0000, Linus Walleij wrote:

On Wed, Feb 25, 2015 at 4:11 PM, Liviu Dudau [off-list ref] wrote:

quoted

On Wed, Feb 25, 2015 at 03:00:23PM +0000, Will Deacon wrote:

quoted

On Wed, Feb 25, 2015 at 02:47:56PM +0000, Liviu Dudau wrote:

quoted

On Wed, Feb 25, 2015 at 01:55:12PM +0000, Will Deacon wrote:

quoted

On Wed, Feb 25, 2015 at 12:16:29PM +0000, Linus Walleij wrote:

quoted

This defines the Juno "APB system registers" as a syscon device,
and all the LEDs controlled by the APB system registers right
below it using the syscon LEDs driver on top of syscon. Define
LED0 for heartbeat, LED1 for MMC0 activity and the following
four LEDs indicating CPU activity using the Linux-specific
DT bindings for triggers.

This is the pattern and same drivers as used on the legacy
platform device trees for the ARM Integrators and the RealView
PB1176.

Stupid question, but where are these LEDs located on the platform? I tried
enabling this, but all it seemed to do was make hackbench slightly slower :)

http://infocenter.arm.com/help/topic/com.arm.doc.ddi0524c/deb1353593789871.html

Section 1.3, look at the left hand side, above the user push buttons.

Right, so these LEDs are *inside* the case. Is that really something worth
enabling for defconfig?

Depends on the case :) You might have a nice cutout in the plastic of the VExpress
box, or have your own custom acrylic box.

Of course I take off the lid, who doesn't want to see the nice electronics.
This is analogous to using some other naked ARM reference design
like the Versatile or the RealView PB1176 where you can just put your
fingers on the board if you like.

quoted

Maybe Linus can explain to us why he thinks this functionality is useful given
that quite a lot of people tend to use the Juno boards inside the original boxes
for fear of ESD accidents.

Wut? Ask the guy who designed the box.

Notice that the SD card slot is *ALSO* inside the box, do you mean we
should then also delete the uSD card support added in
commit 71f867ec130e3cc8e692366fdf8941ded27c727e
by yourself because the SD card slot is not reachable?
Notice that to access that card slot you even have to remove the
nice blue ARM boilerplate.

That's not my view. I have a mobile phone with an uSD card slot, but I have to take
the cover off (and the battery) to access it. It doesn't mean I should not be able
to use it from kernel side because of that, only that the designer of the phone
(and of the Juno board + box by extension) did not expect people to use it with
covers off all the time.


<virtual-tongue-in-cheek-on>
I fail to see why you need to remove the SD card all the time. Surely opening
the case once to put the uSD card in is enough? ;)
</virtual-tongue-in-cheek-on>

The board is obviously designed to be reachable and the top part
of the case is obviously designed to be taken off by professional
users.

I'm mostly on your side, Linus, I was just looking for more use cases. Like I've said,
most of our customers seem to keep the case closed (or at least that is what they tell
us :) ) so I'm looking for explanations on how you use the LEDs (visual debugging for
big-LITTLE was how Lorenzo was using them on TC2 for example).

Best regards,
Liviu

Yours,
Linus Walleij

-- 
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