linux-kernel - Re: [PATCH v2 09/10] irqchip: ti-sci-inta: Add support for Interrupt Aggregator driver

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Message-ID: <2207fc72-22a6-b216-7b98-7c8c7768f002@oracle.com>
Date:   Wed, 31 Oct 2018 11:48:00 -0700
From:   Santosh Shilimkar <santosh.shilimkar@...cle.com>
To:     Marc Zyngier <marc.zyngier@....com>,
        Grygorii Strashko <grygorii.strashko@...com>,
        Lokesh Vutla <lokeshvutla@...com>
Cc:     Nishanth Menon <nm@...com>,
        Santosh Shilimkar <ssantosh@...nel.org>,
        Rob Herring <robh+dt@...nel.org>, tglx@...utronix.de,
        jason@...edaemon.net,
        Linux ARM Mailing List <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel@...r.kernel.org, Tero Kristo <t-kristo@...com>,
        Sekhar Nori <nsekhar@...com>,
        Device Tree Mailing List <devicetree@...r.kernel.org>,
        Peter Ujfalusi <peter.ujfalusi@...com>
Subject: Re: [PATCH v2 09/10] irqchip: ti-sci-inta: Add support for Interrupt
 Aggregator driver

On 10/31/2018 11:42 AM, Marc Zyngier wrote:
> On 31/10/18 18:38, Santosh Shilimkar wrote:
>> On 10/31/2018 11:21 AM, Marc Zyngier wrote:
>>> Hi Grygorii,
>>>
>>
>> [...]
>>
>>>
>>> Well, I'm convinced that we do not want a networking driver to be tied
>>> to an interrupt architecture, and that the two should be completely
>>> independent. But that's my own opinion. I can only see two solutions
>>> moving forward:
>>>
>>> 1) You make the IA a real interrupt controller that exposes real
>>> interrupts (one per event), and write your networking driver
>>> independently of the underlying interrupt architecture.
>>>
>>> 2) you make the IA an integral part of your network driver, not exposing
>>> anything outside of it, and limiting the interactions with the IR
>>> *through the standard IRQ API*. You duplicate this knowledge throughout
>>> the other client drivers.
>>>
>>> I believe that (2) would be a massive design mistake as it locks the
>>> driver to a single of the HW (and potentially a single revision of the
>>> firmware) while (1) gives you the required level of flexibility by
>>> hiding the whole event "concept" at a single location.
>>>
>>> Yes, (1) makes you rewrite your existing, out of tree drivers. Oh well...
>>>
>> My preference is also not tie the network driver with IA. BTW, this is
>> very standard functionality with other network drivers too. And this
>> is handled using MSI-X.
>>
>> So strong NO for 1) from me as well.
> 
> Err. Are you opposing to (1) or (2)? From the above, I cannot really
> tell... ;-)
> 
I mixed it up, sorry. I meant NO for (2), i.e No for making IA part of
the network driver.

Regards,
Santosh