Subject: Re: [PATCH v2 1/2] powerpc/mpic: Add Open-PIC global timer document

From: Scott Wood <[email-masked]>
Date: Mon, 13 Aug 2012 12:39:54 -0500

On 08/13/2012 12:40 AM, Wang Dongsheng-B40534 wrote:
>>> diff --git a/Documentation/devicetree/bindings/open-pic.txt
>>> b/Documentation/devicetree/bindings/open-pic.txt
>>> index 909a902..045c2e9 100644
>>> --- a/Documentation/devicetree/bindings/open-pic.txt
>>> +++ b/Documentation/devicetree/bindings/open-pic.txt
>>> @@ -92,6 +92,52 @@ Example 2:
>>>
>>>  * References
>>>
>>> +* Open PIC global timers
>>> +
>>> +Required properties:
>>> +- compatible: "open-pic,global-timer"
>>
>> open-pic isn't a vendor (or software project that acts like a
>> pseudo-vendor) -- I'd go with "open-pic-global-timer".
>>
> [Wang Dongsheng] yes, "open-pic-global-timer" looks good.
> 
>>> +- reg : Contains two regions.  The first is the timer frequency
>>> +reporting
>>> +  register for the group.  The second is the main timer register bank
>>> +  (GTCCR, GTBCR, GTVPR, GTDR).
>>
>> Why not just put clock-frequency in the node, instead of describing TFRR?
>> I don't think U-Boot currently sets TFRR.
>>
> [Wang Dongsheng] If during startup U-Boot do not set TFRR that is unreasonable.

Too bad, it's what happens and we're not going to force users to update
U-Boot because of this.

>>> +Example 2:
>>> +
>>> +	timer: timer@010f0 {
>>> +		compatible = "open-pic,global-timer";
>>> +		device_type = "open-pic";
>>> +		reg = <0x010f0 4 0x01100 0x100>;
>>> +		interrupts = <0 0 3 0
>>> +			      1 0 3 0
>>> +			      2 0 3 0
>>> +		              3 0 3 0>;
>>> +	};
>>
>> 4-cell interrupt specifiers are specific to Freescale MPICs.  This means
>> there's no way to describe the timer interrupt on a non-Freescale openpic.
>> Again, I suggest we not bother with this in the absence of an actual need
>> to support the timer on non-Freescale openpic in partitioned scenarios.
>> The existing openpic node is sufficient to describe the
>> hardware in the absence of partitioning.   We could have an
>> "openpic-no-timer" property to indicate that we're describing it
>> separately, so that the absence of a timer node isn't ambiguous as to
>> whether it's an old tree or a partitioned scenario.  An fsl,mpic
>> compatible would imply openpic-no-timer.
>>
>> Note that I believe many of the non-Freescale openpic nodes are going to
>> be found on systems with real Open Firmware, so we can't go changing the
>> device tree for them.
> [Wang Dongsheng] In the Open-PIC specification, there are four timer.
> 		interrupts = <0 0 3 0
> 			      1 0 3 0
> 			      2 0 3 0
> 		              3 0 3 0>;
> 
> The "interrupts" just let user know there are four timers. Usage based "interrupts"
> binding to change dts.

I can't understand the above or how it's a response to what I wrote.

-Scott