Re: [PATCH v2 1/4] ARM: dts: omap5: Update GPIO with address space and interrupts

[Sebastien Guiriec <s-guiriec@ti.com>]

Hi Benoit and John,

On 10/23/2012 06:07 PM, Benoit Cousson wrote:
> On 10/23/2012 05:59 PM, Jon Hunter wrote:
>>
>> On 10/23/2012 10:09 AM, Benoit Cousson wrote:
>>> On 10/23/2012 04:49 PM, Jon Hunter wrote:
>>>> Hi Seb,
>>>>
>>>> On 10/23/2012 03:37 AM, Sebastien Guiriec wrote:
>>>>> Add base address and interrupt line inside Device Tree data for
>>>>> OMAP5
>>>>>
>>>>> Signed-off-by: Sebastien Guiriec <s-guiriec@ti.com>
>>>>> ---
>>>>>   arch/arm/boot/dts/omap5.dtsi |   16 ++++++++++++++++
>>>>>   1 file changed, 16 insertions(+)
>>>>>
>>>>> diff --git a/arch/arm/boot/dts/omap5.dtsi b/arch/arm/boot/dts/omap5.dtsi
>>>>> index 42c78be..9e39f9f 100644
>>>>> --- a/arch/arm/boot/dts/omap5.dtsi
>>>>> +++ b/arch/arm/boot/dts/omap5.dtsi
>>>>> @@ -104,6 +104,8 @@
>>>>>
>>>>>   		gpio1: gpio@4ae10000 {
>>>>>   			compatible = "ti,omap4-gpio";
>>>>> +			reg = <0x4ae10000 0x200>;
>>>>> +			interrupts = <0 29 0x4>;
>>>>>   			ti,hwmods = "gpio1";
>>>>>   			gpio-controller;
>>>>>   			#gpio-cells = <2>;
>>>>
>>>> I am wondering if we should add the "interrupt-parent" property to add
>>>> nodes in the device-tree source. I know that today the interrupt-parent
>>>> is being defined globally, but when device-tree maps an interrupt for a
>>>> device it searches for the interrupt-parent starting the current device
>>>> node.
>>>>
>>>> So in other words, for gpio1 it will search the gpio1 binding for
>>>> "interrupt-parent" and if not found move up a level and search again. It
>>>> will keep doing this until it finds the "interrupt-parent".
>>>>
>>>> Therefore, I believe it will improve search time and hence, boot time if
>>>> we have interrupt-parent defined in each node.
>>>
>>> Mmm, I'm not that sure. it will increase the size of the blob, so
>>> increase the time to load it and then to parse it. Where in the current
>>> case, it is just going up to the parent node using the already
>>> un-flatten tree in memory and thus that should not take that much time.
>>
>> Yes it will definitely increase the size, so that could slow things down.
>>
>>> That being said, it might be interesting to benchmark that to see what
>>> is the real impact.
>>
>> Right, I wonder what the key functions are we need to benchmark to get
>> an overall feel for what is best? Right now I am seeing some people add
>> the interrupt-parent for device nodes and others not. Ideally we should
>> be consistent, but at the same time it is probably something that we can
>> easily sort out later. So not a big deal either way.
>
> For consistency, I'd rather not add it at all for the moment.
> Later, when we will only support DT boot, people will start complaining
> about the boot time increase and then we will start optimizing a little
> bit :-)

I just do it like that to be consistent with what is inside OMAP4 dtsi 
for those IPs (GPIO/UART/MMC/I2C). Now after checking Peter already add 
the interrupt-parent for all audio IPs (OMAP3/4/5). But here we need 
also interrupts name. So here we should try to be consistent.

So I can send back the series for OMAP5 and update the OMAP4 with
   interrupts-parent = <&gic>

As of today we are not consistent.

>
> Regards,
> Benoit
>
>