[PATCH v2 2/3] IRQ/Gic-V3: Change arm-gic-its to support the Mbigen interrupt

[majun258@huawei.com (majun (F))]

? 2015/6/19 7:52, Thomas Gleixner ??:
> On Mon, 15 Jun 2015, majun (F) wrote:
>> ? 2015/6/12 18:48, Thomas Gleixner ??:
>>> Can you please provide a proper description of this mbigen chip and
>>> explain WHY you think that it needs all this special hackery?
> 
> You carefully avoided to provide a proper description of this mbigen
> chip and how it needs to be integrated into the GIC/ITS whatever
> scenario.
> 
Mbigen means Message Based Interrupt Generator.
Its a kind of interrupt controller collects
the interrupts from external devices and generate msi interrupt.

Mbigen is applied to reduce the number of wire connected interrupts.

As the peripherals increasing, the interrupts lines needed is increasing
much, especially on the Arm64 server soc.

Therefore, the interrupt pin in gic is not enought for so many perpherals.

Mbigen is designed to fix this problem.

Mbigen chip locates in ITS or outside of ITS.

The working flow of Mbigen shows as below:

external devices ------> MBIGEN ------->ITS

The devices connect to Mbigen chip through wire connecting way.
Mbigen detects and collectes the interrupts from the these devices.

Then, Mbigen generats the MBI interrupts by writting the ITS
Translator register.