linux-kernel - Re: [PATCH 2/2] irqchip: Add RZ/G2L IA55 Interrupt Controller driver

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Date:   Fri, 29 Apr 2022 11:53:13 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     "Lad, Prabhakar" <prabhakar.csengg@...il.com>
Cc:     Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        Marc Zyngier <maz@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Biju Das <biju.das.jz@...renesas.com>
Subject: Re: [PATCH 2/2] irqchip: Add RZ/G2L IA55 Interrupt Controller driver

Hi Prabhakar,

On Fri, Apr 29, 2022 at 11:43 AM Lad, Prabhakar
<prabhakar.csengg@...il.com> wrote:
> On Thu, Apr 28, 2022 at 10:42 AM Geert Uytterhoeven
> <geert@...ux-m68k.org> wrote:
> > On Fri, Apr 22, 2022 at 12:12 AM Lad Prabhakar
> > <prabhakar.mahadev-lad.rj@...renesas.com> wrote:
> > > Add a driver for the Renesas RZ/G2L Interrupt Controller.
> > >
> > > This supports external pins being used as interrupts. It supports
> > > one line for NMI, 8 external pins and 32 GPIO pins (out of 123)
> > > to be used as IRQ lines.
> > >
> > > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>

> > > --- /dev/null
> > > +++ b/drivers/irqchip/irq-renesas-rzg2l.c
> > > @@ -0,0 +1,447 @@
> > > +// SPDX-License-Identifier: GPL-2.0
> > > +/*
> > > + * Renesas RZ/G2L IRQC Driver
> > > + *
> > > + * Copyright (C) 2022 Renesas Electronics Corporation.
> > > + *
> > > + * Author: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> > > + */
> > > +
> > > +#include <linux/clk.h>
> > > +#include <linux/err.h>
> > > +#include <linux/io.h>
> > > +#include <linux/irqchip.h>
> > > +#include <linux/irqdomain.h>
> > > +#include <linux/of_address.h>
> > > +#include <linux/reset.h>
> > > +#include <linux/spinlock.h>
> > > +
> > > +#define IRQC_IRQ_START                 1
> > > +#define IRQC_IRQ_COUNT                 8
> > > +#define IRQC_TINT_START                        9
> >
> > = IRQC_IRQ_START + IRQC_IRQ_COUNT
> >
> OK
>
> > > +#define IRQC_TINT_COUNT                        32
> > > +#define IRQC_NUM_IRQ                   41
> >
> > = IRQC_TINT_START + IRQC_TINT_COUNT
> >
> OK.
>
> > Should these be in a DT binding header file?
> >
> > Combining all types into a single linear number space makes it hard
> > to extend the range, when reusing for an SoC that supports more
> > interrupt sources.
> >
> Or  DT data maybe?

Let's leave it for now. As I missed that DT consumers will refer to
external interrupt numbers only (is that actually enforced?), there
won't be an issue.

The driver can be changed later to derive IRQC_IRQ_COUNT from the
compatible value, when needed.

> > > +       u32 reg;
> > > +
> > > +       reg = readl_relaxed(priv->base + ISCR);
> > > +       if (reg & bit)
> > > +               writel_relaxed(GENMASK(IRQC_IRQ_COUNT - 1, 0) & ~bit,
> >
> > As writes to the unused upper bits are ignored, you can drop the
> > masking with GENMASK(IRQC_IRQ_COUNT - 1, 0), and be prepared for more
> > interrupt sources.
> >
> Agreed.

> > > +       u32 bit = BIT(hw_irq - IRQC_TINT_START);
> > > +       u32 reg;
> > > +
> > > +       reg = readl_relaxed(priv->base + TSCR);
> > > +       if (reg & bit)
> > > +               writel_relaxed(GENMASK(IRQC_TINT_COUNT - 1, 0) & ~bit,
> >
> > Drop the masking with all-ones?
> >
> You mean instead of a mask just use the reg instead?

No, I meant to drop the masking with GENMASK(IRQC_TINT_COUNT - 1, 0),
cfr. for external interrupts.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds