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

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Message-ID: <18df8960-9165-ba50-2c25-9f00d32198e8@oracle.com>
Date:   Wed, 31 Oct 2018 11:38:00 -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 11:21 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.

regards,
Santosh