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

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Date:   Fri, 27 Nov 2020 20:53:28 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     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 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!
--
Florian