Subject: [PATCH 1/3] misc: Add crossbar driver

From: [email-masked] (Sricharan R)
Date: Tue, 13 Aug 2013 15:26:10 +0530

Hi Tony,

On Tuesday 13 August 2013 01:40 PM, Tony Lindgren wrote:
> * Santosh Shilimkar <[email-masked]> [130724 12:06]:
>> On Wednesday 24 July 2013 02:51 PM, Nishanth Menon wrote:
>>> On 07/24/2013 01:43 PM, Sricharan R wrote:
>>>> On Wednesday 24 July 2013 10:17 PM, Nishanth Menon wrote:
>>>>> On 07/24/2013 11:38 AM, Santosh Shilimkar wrote:
>>>>>> On Wednesday 24 July 2013 12:08 PM, Nishanth Menon wrote:
>>>>>>> That said, maybe a intermediate pinctrl approach might be more pragmatic and less theoretically flexible.
>>>>>>> an option might be to "statically allocate" default number of interrupts to a domain - example:
>>>>>>> * GIC IRQ 72->78 allotted to UARTs
>>>>>>> * pinctrl mapping provided for those but only 6 can be used (rest are marked status="disabled" as default) at any given time (choice of pinctrl option determines GIC interrupt line to use)
>>>>>>> * All modules will have a pinctrl definition to have a mapping - to avoid bootloader overriding default cross bar setting in ways un-expected by kernel.
>>>>>>>
>>>>>>> Does that sound fair trade off?
>>>>>> This sounds better. That way we can get all the devices in the DT at least.
>>>>> Fair enough - if Linus and Tony are still ok with this approach to the problem, seeing a patch series with the effect would be beneficial.
>>>>>
>>>>   Ok, i will use this idea of certain number interrupts to groups.
>>>> Yes on DRA7XX, we have about 160 gic lines and 320 irq crossbar device inputs contending for it.
>>>> 1:2 and fully arbitrary.  But will we be really exhausting them ?
>>>>
>>> Depends on how we allocate :). The default arbitary allocation can be made more logical in your series ofcourse :).
>>>
>> I would just most logical peripherals rather than providing every single
>> IP connected to cross bar. Otherwise we will end up wth hwmod like
>> scenario where now started removing the unused stuff because of
>> maintenance and loc issues ;-)
> Sorry for the delay on this, I think the best way to set this up
> is as a separate drivers/irqchip controller. Then just map the
> configured interrupts for the board with interrupt-map and
> interrupt-map-mask binding. No need to stuff all the SoC specific
> maps to the .dts, just the ones used for the board.
>
> Regards,
>
> Tony
>  
 Initially irqchip was discussed, but we also have a DMA crossbar
 to map the dma-requests. Since both irq/dma crossbars should be handled,
 pinctrl was suggested as the appropriate place to handle this.

Regards,
 Sricharan