linux-kernel - Re: [DO NOT MERGE v5 11/37] pci: pci-sh7751: Add SH7751 PCI driver

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Message-ID: <CACRpkdZUAMXJ4YM9+xW2Snzt0Dx5mxWjcwHZifsXPJH9ozL5bg@mail.gmail.com>
Date:   Tue, 5 Dec 2023 22:48:41 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        linux-sh@...r.kernel.org, Damien Le Moal <dlemoal@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Dave Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
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        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
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        linux-fbdev@...r.kernel.org
Subject: Re: [DO NOT MERGE v5 11/37] pci: pci-sh7751: Add SH7751 PCI driver

On Tue, Dec 5, 2023 at 2:26 PM Arnd Bergmann <arnd@...db.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] = memory_start;
> > +             memory[1] = 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