linux-kernel - Re: [PATCH v2 01/14] dt-bindings: remoteproc: Add TI PRUSS bindings

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Date:   Thu, 14 Feb 2019 17:44:36 +0200
From:   Roger Quadros <rogerq@...com>
To:     Marc Zyngier <marc.zyngier@....com>, Suman Anna <s-anna@...com>,
        "Davis, Andrew" <afd@...com>, Lokesh Vutla <lokeshvutla@...com>
CC:     Linus Walleij <linus.walleij@...aro.org>,
        Lokesh Vutla <lokeshvutla@...com>,
        ext Tony Lindgren <tony@...mide.com>,
        Ohad Ben-Cohen <ohad@...ery.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        David Lechner <david@...hnology.com>,
        "Nori, Sekhar" <nsekhar@...com>, Tero Kristo <t-kristo@...com>,
        <nsaulnier@...com>, <jreeder@...com>,
        Murali Karicheri <m-karicheri2@...com>,
        <woods.technical@...il.com>,
        Linux-OMAP <linux-omap@...r.kernel.org>,
        <linux-remoteproc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.or>
Subject: Re: [PATCH v2 01/14] dt-bindings: remoteproc: Add TI PRUSS bindings

On 14/02/19 14:52, Marc Zyngier wrote:
> On Thu, 14 Feb 2019 10:55:10 +0000,
> Roger Quadros <rogerq@...com> wrote:
>>
>>
>> On 14/02/19 10:37, Linus Walleij wrote:
>>> On Thu, Feb 14, 2019 at 4:13 AM Suman Anna <s-anna@...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.

> If these assertions do hold, then your design is typical of a
> hierarchy, for which we have countless examples in the tree (including
> for some TI HW).

OK.
Suman, Andrew, Lokesh, thoughts?

-- 
cheers,
-roger
Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
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