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From:   "Lad, Prabhakar" <prabhakar.csengg@gmail.com>
Date:   Mon, 2 May 2022 06:21:34 +0100
Message-ID: <CA+V-a8suzvW8yLvuj=Knf895KaGmQEghP2R8u_ki3MSFA5pTwQ@mail.gmail.com>
Subject: Re: [PATCH 2/2] irqchip: Add RZ/G2L IA55 Interrupt Controller driver
To:     Geert Uytterhoeven <geert@linux-m68k.org>
Cc:     Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>,
        Marc Zyngier <maz@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
        Biju Das <biju.das.jz@bp.renesas.com>
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Precedence: bulk

Hi Geert,

On Fri, Apr 29, 2022 at 10:59 AM Lad, Prabhakar
<prabhakar.csengg@gmail.com> wrote:
>
> Hi Geert,
>
> On Fri, Apr 29, 2022 at 10:53 AM Geert Uytterhoeven
> <geert@linux-m68k.org> wrote:
> >
> > Hi Prabhakar,
> >
> > On Fri, Apr 29, 2022 at 11:43 AM Lad, Prabhakar
> > <prabhakar.csengg@gmail.com> wrote:
> > > On Thu, Apr 28, 2022 at 10:42 AM Geert Uytterhoeven
> > > <geert@linux-m68k.org> wrote:
> > > > On Fri, Apr 22, 2022 at 12:12 AM Lad Prabhakar
> > > > <prabhakar.mahadev-lad.rj@bp.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@bp.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@bp.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.
> >
> Agreed.
>
> > > > > +       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.
> >
> Ahh right, I missed that.
>
I would need reg to clear off the bit if I drop the mask.

Cheers,
Prabhakar