Hi.
27.04.2015 23:54, Pavel Machek пишет:
Hi!
The following patches improve the precision of led
timer trigger and add the delay unit control.
That allows to make PWM brightness control with timer
trigger.
Are you sure that is good idea? Doing LED pwm with main cpu is quite harsh...
Do you remember the pc-speaker driver? :)
In fact I tried the maximal possible freq on armada-xp
board (it doesn't go above approx 100KHz, perhaps this
all the HW timers can do on that board) and I haven't
measured any noticeable CPU load with htop.
We already have "brightness" for... well... brightness level.
Would it make sense to have an option (Kconfig?) to do PWM using timer on hardware
that does not do hardware PWM?
I think it would make sense, but not for the "timer" trigger.
Maybe for "none" trigger, or inventing another trigger called
"pwm".
For the timer trigger I would pretty much like my approach to stay.
The reason is that the PWM I need to do, is not strictly a PWM -
it needs the ON period in range of tens or hundreds of milliseconds,
while the OFF period is in a couple of usecs (or vice-versa). No
generic PWM driver can afford such distribution, so I'd like to have
the "timer" trigger for the unusual things like that.
As I said, your idea can still be implemented for "none" trigger
or some new trigger, so its still all for good.
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