linux-kernel - Re: [PATCHv3 2/6] irqchip/irq-pruss-intc: Add a PRUSS irqchip driver for PRUSS interrupts

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Message-ID: <53d39d8fbd63c6638dbf0584c7016ee0@kernel.org>
Date:   Sun, 05 Jul 2020 21:45:36 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     Grzegorz Jaszczyk <grzegorz.jaszczyk@...aro.org>
Cc:     tglx@...utronix.de, jason@...edaemon.net,
        "Anna, Suman" <s-anna@...com>, robh+dt@...nel.org,
        Lee Jones <lee.jones@...aro.org>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, david@...hnology.com,
        "Mills, William" <wmills@...com>, "Andrew F . Davis" <afd@...com>,
        Roger Quadros <rogerq@...com>
Subject: Re: [PATCHv3 2/6] irqchip/irq-pruss-intc: Add a PRUSS irqchip driver
 for PRUSS interrupts

On 2020-07-05 14:26, Grzegorz Jaszczyk wrote:
> On Sat, 4 Jul 2020 at 11:39, Marc Zyngier <maz@...nel.org> wrote:
>> 
>> On 2020-07-03 15:28, Grzegorz Jaszczyk wrote:

[...]

>> It still begs the question: if the HW can support both edge and level
>> triggered interrupts, why isn't the driver supporting this diversity?
>> I appreciate that your HW may only have level interrupts so far, but
>> what guarantees that this will forever be true? It would imply a 
>> change
>> in the DT binding, which isn't desirable.
> 
> Ok, I've got your point. I will try to come up with something later
> on. Probably extending interrupt-cells by one and passing interrupt
> type will be enough for now. Extending this driver to actually support
> it can be handled later if needed. Hope it works for you.

Writing a set_type callback to deal with this should be pretty easy.
Don't delay doing the right thing.

[...]

>> >> > +             hwirq = hipir & GENMASK(9, 0);
>> >> > +             virq = irq_linear_revmap(intc->domain, hwirq);
>> >>
>> >> And this is where I worry. You seems to have a single irqdomain
>> >> for all the muxes. Are you guaranteed that you will have no
>> >> overlap between muxes? And please use irq_find_mapping(), as
>> >> I have top-secret plans to kill irq_linear_revmap().
>> >
>> > Regarding irq_find_mapping - sure.
>> >
>> > Regarding irqdomains:
>> > It is a single irqdomain since the hwirq (system event) can be mapped
>> > to different irq_host (muxes). Patch #6
>> > https://lkml.org/lkml/2020/7/2/616 implements and describes how input
>> > events can be mapped to some output host interrupts through 2 levels
>> > of many-to-one mapping i.e. events to channel mapping and channels to
>> > host interrupts. Mentioned implementation ensures that specific system
>> > event (hwirq) can be mapped through PRUSS specific channel into a
>> > single host interrupt.
>> 
>> Patch #6 is a nightmare of its own, and I haven't fully groked it yet.
>> Also, this driver seems to totally ignore the 2-level routing. Where
>> is it set up? map/unmap in this driver do exactly *nothing*, so
>> something somewhere must set it up.
> 
> The map/unmap is updated in patch #6 and it deals with those 2-level
> routing setup. Map is responsible for programming the Channel Map
> Registers (CMRx) and Host-Interrupt Map Registers (HMRx) basing on
> provided configuration from the one parsed in the xlate function.
> Unmap undo whatever was done on the map. More details can be found in
> patch #6.
> 
> Maybe it would be better to squash patch #6 with this one so it would
> be less confusing. What is your advice?

So am I right in understanding that without patch #6, this driver does
exactly nothing? If so, it has been a waste of review time.

Please split patch #6 so that this driver does something useful
for Linux, without any of the PRU interrupt routing stuff. I want
to see a Linux-only driver that works and doesn't rely on any other
exotic feature.

         M.
-- 
Jazz is not dead. It just smells funny...