Hey Ricardo,
On 11-05-16 23:38, Ricardo Ribalda Delgado wrote:
Some update
I have not received anything to test it and I will be out of the
office from today until the 30th :S. So it seems that I have not way
to test the changes.
That's understandable, meanwhile I've been running some experiments and
mostly reading the datasheet more closely. You hadn't replied to my
earlier mention of it so I'll only talk about that now.
Right now, the GDC (e.g. GRPPWM) register is set via some math using the
period:
/*
* From manual: duty cycle = (GDC / 256) ->
* (time_on / period) = (GDC / 256) ->
* GDC = ((time_on * 256) / period)
*/
gdc = (time_on * 256) / period;
This is wrong in my opinion, as the manual states:
When DMBLNK bit is programmed with 1, GRPPWM and GRPFREQ registers define a
global blinking pattern, where GRPFREQ contains the blinking period
(from 24 Hz to
10.73 s) and GRPPWM the duty cycle (ON/OFF ratio in %).
First, when DMBLNK is programmed with 0, GRPFREQ is a don't care, so no
'blinking' takes place. Which means, since we want blink_set to work, we
need DMBLNK and that can be enabled by default, as the LDR register
controls whether we can blink at all (11b vs 10b)
Then the GRPFREQ register, as done now, sets a frequency for the blink
between 41ms and 10.73 seconds.
Finally, the GRPPWM/gdc register can be used to globally control the
brightness of leds which are linked (via LDR=11b). So if we have a color
setup, e.g. #4488FF and we globally dim this color via gdc to 10%, we
get #04080F on the output. To add this behavior we'd be adding some more
hacks as the led framework doesn't really support linked outputs at all,
(nice new feature, to link leds together with a global control?, other
subsystems do something like that, cpufreq i guess) who decides the
value of gdc. There is no toggle to set the global brightness. What
could be possible, is to leave whatever setting is in the brightness and
read/report the individual led brightness as it where the gdc. Which
could actually work thinking about it. But (and I think it is impossible
now anyway) it would break individual color control during the blink.
e.g. /sys/class/led/[red,green,blue]/brightness are always equal and
writing to either during blink sets the global brightness.
But that should be a separate patch that I'm thinking a bit more about.
So for now, I recommend to set GRPPWM initially to 0xff, e.g. leds full
on, until the above patch is added. We then blink at whatever color is
set to the output and only control the blink via the GRPFREQ, without
the possibility to change brightness during a blink.
Olliver
Sorry about that.
Regards!
On Fri, Apr 22, 2016 at 10:48 AM, Ricardo Ribalda Delgado
<ricardo.ribalda@xxxxxxxxx> wrote:
Hi
I am on trip until next monday. I have arranged also some hw to be sent to
me that day.
Can we continue the conversation then? I know I told you that I will review
this yesterday, but I did not have the time , sorry
Regards!
On 22 Apr 2016 09:21, "Olliver Schinagl"<oliver@xxxxxxxxxxx> wrote:
Hi Ricardo,
On 20-04-16 11:17, Ricardo Ribalda Delgado wrote:
Hello again
On Wed, Apr 20, 2016 at 11:06 AM, Olliver Schinagl<oliver@xxxxxxxxxxx>
wrote:
The devil is in the details :)
:)
Saving mode2 sounds like a good compromise then.
But I still believe that we should limit the lock to ledout. No matter
what we do, we cannot have two leds blinking at different frequencies
on the same chip.
So to save a mutex a little bit, we take the risk that nobody else
enables
the blink or if they do, enable it in the same way?
If it saves so much, then I guess its worth the risk I suppose?
Give me a day to go through the chip doc and see if I can find a good
compromise, that at least warranties that the leds that are enable
stay enabled ;)
Right, I also went over the datasheet, and I think we can simplyfy two
things.
For one, yes, move the mode2 register completly to the probe section. Set
the DMBLINK led to always 1. It does not get cleared, I was wrong. We have
to set it to as with 0 we do not get any blinking at all (grpfreq gets
ignored).
Furthermore, we should change:
- gdc = (time_on * 256) / period;
+ gdc = 0x00;
Because the calculation does not make sense. GDC is the global
brightness/pwm/dimming control. It is used to uniformly change the blink
rate on all the linked leds.
"General brightness for the 16 outputs is controlled through 256 linear
steps to FFh"
I don't think that is the intention of the gdc is it? Looking at the
original gdc code, it thus sets the global BRIGHTNESS based on the
period/on_time. I don't think that is what we expect when we enable blink.
From my understanding, the grppwm is super-imposed, thus by setting gdc to
0, we do not superimpose anything and the original brightness is retained.
(If i'm wrong here, we need to set gdc to 0xff.
Because of this, I even recommend removing gdc all together, which saves
another i2c write.
Or am I wrong here?
Olliver
Regards!
--
To unsubscribe from this list: send the line "unsubscribe devicetree" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
