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Subject: Re: [PATCH v2 01/14] dt-bindings: remoteproc: Add TI PRUSS bindings
To:     Marc Zyngier <marc.zyngier@arm.com>, Suman Anna <s-anna@ti.com>,
        "Davis, Andrew" <afd@ti.com>, Lokesh Vutla <lokeshvutla@ti.com>
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CC:     Linus Walleij <linus.walleij@linaro.org>,
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From:   Roger Quadros <rogerq@ti.com>
Message-ID: <5C659C6F.5010000@ti.com>
Date:   Thu, 14 Feb 2019 18:50:55 +0200
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On 14/02/19 17:51, Marc Zyngier wrote:
> On 14/02/2019 15:44, Roger Quadros wrote:
>> On 14/02/19 14:52, Marc Zyngier wrote:
>>> On Thu, 14 Feb 2019 10:55:10 +0000,
>>> Roger Quadros <rogerq@ti.com> wrote:
>>>>
>>>>
>>>> On 14/02/19 10:37, Linus Walleij wrote:
>>>>> On Thu, Feb 14, 2019 at 4:13 AM Suman Anna <s-anna@ti.com> wrote:
>>>>>> [Me]
>>>>>
>>>>>>> To be able to use hierarchical interrupt domain in the kernel, the top
>>>>>>> interrupt controller must use the hierarchical (v2) irqdomain, so
>>>>>>> if this is anything else than the ARM GIC it will be an interesting
>>>>>>> undertaking to handle this.
>>>>>>
>>>>>> These are interrupt lines coming towards the host processor running
>>>>>> Linux and are directly connected to the ARM GIC. This INTC module is
>>>>>> actually an PRUSS internal interrupt controller that can take in 64 (on
>>>>>> most SoCs) external events/interrupt sources and multiplexing them
>>>>>> through two layers of many-to-one events-to-intr channels &
>>>>>> intr-channels-to-host interrupts. Couple of the host interrupts go to
>>>>>> the PRU cores themselves while the remaining ones come out of the IP to
>>>>>> connect to other GICs in the SoC.
>>>>>
>>>>> If the muxing is static (like set up once at probe) so that while
>>>>> the system is running, there is one and one only event mapped to
>>>>> the GIC from the component below it, then it is hierarchical.
>>>>
>>>> This is how it looks.
>>>>
>>>> [GIC]<---8---[INTC]<---64---[events from peripherals]
>>>>
>>>> The 8 interrupt lines from INTC to the GIC are 1:1 mapped and fixed
>>>> per SoC.  The muxing between 64 inputs to INTC and its 8 outputs are
>>>> programmable and might not necessarily be static per boot/probe as
>>>> it depends on what firmware is loaded on the PRU.
>>>
>>> But the point is that at any given time, there are at most 8 out of 64
>>> inputs that are used, right? You *never* end-up with two (or more) of
>>> these "events" being multiplexed on a single output line.
>>>
>>
>> Since the INTC's internal logic allows assigning more than one event each outputs,
>> at most all 64 events can be assigned to one output or distributed among the 8 outputs.
> 
> OK. Do you get individual masking and status bits for each input?

Yes, we have individual enable/disable and status bits for each of the 64 events.

In addition to that it is possible to determine priority if multiple events come to the same
output by reading a register specific to that output.

--
cheers,
-roger
 
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