linux-kernel - Re: [PATCH v2 1/2] arm64: dts: broadcom: clear the warnings caused by empty dma-ranges

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Message-ID: <CAK8P3a1_5RgcPz+bgo1bbUBk8NTJd=1-Y5-=CsQYkFgLfTE3_A@mail.gmail.com>
Date:   Sat, 28 Nov 2020 10:58:38 +0100
From:   Arnd Bergmann <arnd@...nel.org>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     bcm-kernel-feedback-list <bcm-kernel-feedback-list@...adcom.com>,
        Zhen Lei <thunder.leizhen@...wei.com>,
        Rob Herring <robh+dt@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] arm64: dts: broadcom: clear the warnings caused by
 empty dma-ranges

On Sat, Nov 28, 2020 at 5:53 AM Florian Fainelli <f.fainelli@...il.com> wrote:
>
> On Fri, 16 Oct 2020 17:08:32 +0800, Zhen Lei <thunder.leizhen@...wei.com> wrote:
> > The scripts/dtc/checks.c requires that the node have empty "dma-ranges"
> > property must have the same "#address-cells" and "#size-cells" values as
> > the parent node. Otherwise, the following warnings is reported:
> >
> > arch/arm64/boot/dts/broadcom/stingray/stingray-usb.dtsi:7.3-14: Warning \
> > (dma_ranges_format): /usb:dma-ranges: empty "dma-ranges" property but \
> > its #address-cells (1) differs from / (2)
> > arch/arm64/boot/dts/broadcom/stingray/stingray-usb.dtsi:7.3-14: Warning \
> > (dma_ranges_format): /usb:dma-ranges: empty "dma-ranges" property but \
> > its #size-cells (1) differs from / (2)
> >
> > Arnd Bergmann figured out why it's necessary:
> > Also note that the #address-cells=<1> means that any device under
> > this bus is assumed to only support 32-bit addressing, and DMA will
> > have to go through a slow swiotlb in the absence of an IOMMU.
> >
> > Suggested-by: Arnd Bergmann <arnd@...db.de>
> > Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
> > ---
>
> Applied to devicetree-arm64/next, thanks!

The notification may have gone missing, but I had merged it into v5.10-fixes
already, and as of today, it's in mainline, so you can drop it from your
next branch, or just leave it in if you want to avoid taking things out of
your tree.

      Arnd