On 04/09/2018 04:21 PM, Rob Herring wrote:
On Mon, Apr 9, 2018 at 12:38 AM, Mikko Perttunen <cyndis@xxxxxxxx> wrote:
Rob,
Please don't top post to lists.
this binding is for a specific IP block (for measuring/aggregating input
pulses) on the Tegra186 SoC, so I don't think it fits into any generic
binding.
What is it hooked up to to measure? You only mention "fan" five times
in the doc.
In practice, fans.
You have #pwm-cells too, so this block has PWM output as well? If not,
then where's the PWM for the fan control because there is no point in
having fan tach without some control mechanism.
It doesn't provide a PWM output. The (Linux) PWM framework provides
functionality in both directions - control and capture. But if the
device tree #pwm-cells/pwms properties are only for control, we may need
to introduce a new #capture-pwm-cells/capture-pwms or similar.
The idea is that the generic fan node can then specify two pwms, one for
control and one for capture, to enable e.g. closed-loop control (I'm not
personally familiar with the usecase for this but I could imagine
something like that). The control PWM can be something completely
different, maybe not a PWM in the first place (e.g. some fixed voltage).
There's only so many ways to control fans and types of fans, so yes,
the interface of control and feedback lines between a fan and its
controller should absolutely be generic.
I'm not quite getting what you mean by this. Clearly we need a custom
compatibility string for the tachometer as it's a different hardware
block with different programming than others. Or are you complaining
about the nvidia,pulse-per-rev/capture-window-len properties?
Thanks,
Mikko
Rob
Thanks,
Mikko
On 03/27/2018 05:52 PM, Rob Herring wrote:
On Wed, Mar 21, 2018 at 10:10:38AM +0530, Rajkumar Rampelli wrote:
Supply Device tree binding documentation for the NVIDIA
Tegra186 SoC's Tachometer Controller
Signed-off-by: Rajkumar Rampelli <rrajk@xxxxxxxxxx>
---
V2: Renamed compatible string to "nvidia,tegra186-pwm-tachometer"
Renamed dt property values of clock-names and reset-names to
"tachometer"
from "tach"
Read my prior comments on v1.
Rob
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