Re: [PATCH 3/6] Documentation: devicetree: dwc3: Add interrupt moderation

[Felipe Balbi <felipe.balbi-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>]

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Hi,

John Youn <John.Youn-HKixBCOQz3hWk0Htik3J/w@public.gmane.org> writes:
>>>> John Youn <johnyoun-HKixBCOQz3hWk0Htik3J/w@public.gmane.org> writes:
>>>>> Add interrupt moderation interval binding for dwc3.
>>>>>
>>>>> Signed-off-by: John Youn <johnyoun-HKixBCOQz3hWk0Htik3J/w@public.gmane.org>
>>>>> ---
>>>>>  Documentation/devicetree/bindings/usb/dwc3.txt | 1 +
>>>>>  1 file changed, 1 insertion(+)
>>>>>
>>>>> diff --git a/Documentation/devicetree/bindings/usb/dwc3.txt b/Documentation/devicetree/bindings/usb/dwc3.txt
>>>>> index e3e6983..17de9fc 100644
>>>>> --- a/Documentation/devicetree/bindings/usb/dwc3.txt
>>>>> +++ b/Documentation/devicetree/bindings/usb/dwc3.txt
>>>>> @@ -53,6 +53,7 @@ Optional properties:
>>>>>   - snps,quirk-frame-length-adjustment: Value for GFLADJ_30MHZ field of GFLADJ
>>>>>  	register for post-silicon frame length adjustment when the
>>>>>  	fladj_30mhz_sdbnd signal is invalid or incorrect.
>>>>> + - snps,imod_interval: the interrupt moderation interval.
>>>>
>>>> on top of all other comments, what's the unit here? nanoseconds? clock cycles?
>>>>
>>>
>>> Number of 250 ns intervals. I'll update the description to clarify.
>> 
>> it's probably better to add it in nanoseconds itself, then let driver
>> compute register value with DIV_ROUND_UP()
>> 
>
> I'm fine with it either way, but I think "increments of 250 ns" is
> slightly cleaner in that it reflects the exact settings that are
> possible and documented, and also fits neatly into a u16.

I don't know, I'll leave this to Mark and the other devicetree folks,
but I remember there was a preference of not passing register values via
devicetree. What if a following HW revision decides to change 250ns
increments to 125ns increments?

Mark?

-- 
balbi

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