[PATCH 3/4] dt/bindings: Introduce the FSL QorIQ DPAA QMan

Emil Medve Emilian.Medve at Freescale.com
Fri Oct 24 20:53:52 AEDT 2014

Hello Mark,

On 10/23/2014 06:26 AM, Mark Rutland wrote:
>>>> +- clocks
>>>> +	Usage:		See clock-bindings.txt and qoriq-clock.txt
>>>> +	Value type:	<prop-encoded-array>
>>>> +	Definition:	Half of the platform clock
>>>> +
>>> I don't understand the description here. What is the clock from the PoV
>>> of the QMan? Which input line on the QMan is this clock attached to?
>>> Is there only one clock input? Or jsut one that you need to manage at
>>> the moment?
>> As part of the programming model (QoS features specifically) QMan needs
>> to know its clock speed. Prior to the existence of the
>> clock-bindings.txt, a "static" clock-frequency property was/is used
>> convey such information. Using clock-binding.txt to describe the
>> clocking hierarchy in the SoC makes it easier with DFS, power
>> management, etc.
> Ok. My concern is the phrase "Half of the platform clock" is meaingless.
> The property contains a phandle + clock-specifier pair that describe a
> single input clock by reference (some bindings just say "clock
> reference" for that, which is fine). This is not "half" of any
> particular clock.
> The description of the clock should describe what it logically is from
> the PoV of the consumer (i.e. _this_ device) rather than the provider.
> To me "platform clock" sounds like a description of the provider. Is
> there a name for the clock input line on this device?
> Is there only a single clock input? Or just one that you care about at
> the moment?

This is the reference clock for QMan and is the only input clock. It's
derived form the platform PLL/clock and its frequency/speed is half of
the platform PLL. I'll update its description


More information about the Linuxppc-dev mailing list