linux-kernel - Re: [PATCH 2/2] gpio: Add xgs-iproc driver

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Message-ID: <CACRpkdb8o9UU0W1FJ4=KYiV3CUEUkXbR4CFY7XKdJG2O8sSJFA@mail.gmail.com>
Date:   Wed, 16 Oct 2019 14:53:39 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Chris Packham <Chris.Packham@...iedtelesis.co.nz>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "bcm-kernel-feedback-list@...adcom.com" 
        <bcm-kernel-feedback-list@...adcom.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "rjui@...adcom.com" <rjui@...adcom.com>,
        "mark.rutland@....com" <mark.rutland@....com>,
        Richard Laing <Richard.Laing@...iedtelesis.co.nz>,
        "sbranden@...adcom.com" <sbranden@...adcom.com>,
        "bgolaszewski@...libre.com" <bgolaszewski@...libre.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 2/2] gpio: Add xgs-iproc driver

On Mon, Oct 14, 2019 at 12:08 AM Chris Packham
<Chris.Packham@...iedtelesis.co.nz> wrote:
Me:

> > I think this should be a chained interrupt handler (see below how to
> > register it).
> >
> > See e.g. drivers/gpio/gpio-ftgpio010.c for an example:
> > change function prototype, no return value, use
> > chained_irq_enter/exit(irqchip, desc); etc.
> >
>
> I don't think a chained interrupt handler can work. The problem is that
> the parent irq on the SoC is shared between the gpio and uart0 (why
> it's this way with two IP blocks in the same SoC I'll never know). When
> a chained interrupt handler is registered I lose the serial interrupts.
> Please correct me if there is some way to make the chained handlers
> deal with sharing interrupts.

Aha I see. Look at:
drivers/gpio/gpio-mt7621.c

And how that driver sets the parent handler to NULL in order
to still exploit the core helpers.

I will refactor this to some more elegant API at some point when
I get there, for now follow the example of mt7621.

Yours,
Linus Walleij