[PATCH v3 1/3] IRQ/Gic-V3: Add mbigen driver to support mbigen interrupt controller
majun258 at huawei.com
Thu Jul 16 05:26:33 PDT 2015
在 2015/7/16 17:30, Marc Zyngier 写道:
> On 16/07/15 10:22, majun (F) wrote:
>> 在 2015/7/16 16:52, Marc Zyngier 写道:
>>> On 16/07/15 09:35, majun (F) wrote:
>>>>> I'm a bit puzzled.
>>>> For interrupts connect to mbigen , the interrupt trigger type, device id and
>>>> event id value are encoded in mbigen chip already.
>>>> There are two types of mbigen node within a mbigen chip.
>>>> Type1: event id valud can't be programmed.
>>>> Type2: event id value can be programmed.
>>>> For example: An device with 5 interrupts connected to Mbigen node
>>>> type 1.The default event id vlaue encoded in mbigen chip for these 5 interrupt
>>>> is from 0 to 4.
>>>> Because the event id value can't be programmed, we need to define all of
>>>> 5 interrupts in dts file so that these 5 interrupt has
>>> You can define what you want in the device tree, the ITS doesn't care!
>>> Nothing in the ITS code parses this property, and there is absolutely
>>> zero chance that the even the ITS has allocated will actually match what
>>> you expect.
>>> The ITS *relies* on the principle that the evenID can be programmed,
>>> just like any MSI controller relies on the device to be programmed with
>>> whatever payload has been provided. If all of a sudden we have to
>>> support HW that has its own view of the payload, what you have here will
>>> simply not work.
>> "If all of a sudden we have to
>> support HW that has its own view of the payload, what you have here will
>> simply not work."
>> I am not very unstand this case, would you please explain this more detail?
> It is the ITS driver that allocates the eventID, not the device. If your
> hardware has decided that it will use event 5, while the ITS expect it
> to use event 3, nothing will work. And there is no way for the ITS to
> know which event your device is using (it doesn't parse your device's
> device tree).
Yes, I agree with you that eventID should be allocated by ITS driver.
But I want to explain the case you said above can be avoided.
For example, An device with total 5 interrupts connected to Mbigen node.
In mbigen chip, the default eventID value for each device starts from 0.
So, for these 5 interrupts the default eventID value is from 0 to 4.
Because the default eventID is fixed in mbigen chip, to make these 5 interrupt
work, the only way is define all these 5 interrupts in dts file.
When irq initializing, ITS driver will allocat LPI interrupt number for these
5 interrupts, for example : from 8192 to 8196. and the eventID value is from 0 to 4.
Now, the allocated eventID value same as the eventID value encoded in mbigen chip,
The interrupt can work.
I know this is not a good method,but for current mbigen chip,it's the only solution.
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