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From:   Linus Walleij <linus.walleij@linaro.org>
Date:   Tue, 5 Dec 2023 22:48:41 +0100
Message-ID: <CACRpkdZUAMXJ4YM9+xW2Snzt0Dx5mxWjcwHZifsXPJH9ozL5bg@mail.gmail.com>
Subject: Re: [DO NOT MERGE v5 11/37] pci: pci-sh7751: Add SH7751 PCI driver
To:     Arnd Bergmann <arnd@arndb.de>
Cc:     Yoshinori Sato <ysato@users.sourceforge.jp>,
        linux-sh@vger.kernel.org, Damien Le Moal <dlemoal@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>,
        Dave Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        Thomas Gleixner <tglx@linutronix.de>,
        Lorenzo Pieralisi <lpieralisi@kernel.org>,
        =?UTF-8?Q?Krzysztof_Wilczy=C5=84ski?= <kw@linux.com>,
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        Magnus Damm <magnus.damm@gmail.com>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Rich Felker <dalias@libc.org>,
        John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
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        Biju Das <biju.das.jz@bp.renesas.com>,
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        Sergey Shtylyov <s.shtylyov@omp.ru>,
        Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>,
        linux-ide@vger.kernel.org, devicetree@vger.kernel.org,
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        Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
        linux-clk@vger.kernel.org, dri-devel@lists.freedesktop.org,
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On Tue, Dec 5, 2023 at 2:26=E2=80=AFPM Arnd Bergmann <arnd@arndb.de> wrote:
> On Tue, Dec 5, 2023, at 10:45, Yoshinori Sato wrote:

> > +     if (of_property_read_u32_array(pdev->dev.of_node,
> > +                                    "renesas,memory", memory, 2) < 0) =
{
> > +             /*
> > +              * If no memory range is specified,
> > +              *  the entire main memory will be targeted for DMA.
> > +              */
> > +             memory[0] =3D memory_start;
> > +             memory[1] =3D memory_end - memory_start;
> > +     }
>
> There is a generic "dma-ranges" proerty for describing
> which memory is visible by a bus.

It's really a headache to use, so I put a bit of documentation here:
https://elinux.org/Device_Tree_Usage#PCI_DMA_Address_Translation

Yoshinoro, you can look at these bindings and drivers that use
dma-ranges for help:
Documentation/devicetree/bindings/pci/intel,ixp4xx-pci.yaml
drivers/pci/controller/pci-ixp4xx.c
Documentation/devicetree/bindings/pci/faraday,ftpci100.yaml
drivers/pci/controller/pci-ftpci100.c

Yours,
Linus Walleij