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From:   Arnd Bergmann <arnd@kernel.org>
Date:   Tue, 15 Dec 2020 16:49:10 +0100
Message-ID: <CAK8P3a1TViQopQNFE4+Dtac0v2CneGiy22WYu5BuYv8HX2r8Lg@mail.gmail.com>
Subject: Re: [PATCH v2 1/2] arm64: dts: broadcom: clear the warnings caused by
 empty dma-ranges
To:     Florian Fainelli <f.fainelli@gmail.com>
Cc:     Bharat Gooty <bharat.gooty@broadcom.com>,
        Ray Jui <ray.jui@broadcom.com>,
        devicetree <devicetree@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Scott Branden <sbranden@broadcom.com>,
        Ray Jui <rjui@broadcom.com>,
        linux-arm-msm <linux-arm-msm@vger.kernel.org>,
        Andy Gross <agross@kernel.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Rob Herring <robh+dt@kernel.org>,
        bcm-kernel-feedback-list <bcm-kernel-feedback-list@broadcom.com>,
        Zhen Lei <thunder.leizhen@huawei.com>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
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On Tue, Dec 15, 2020 at 4:41 PM Florian Fainelli <f.fainelli@gmail.com> wrote:
>
> On 12/15/2020 5:19 AM, Bharat Gooty wrote:
> > Since the IOMMU is disabled and DMA engine is on 32-bit bus, We can not
> > give the complete DDR for the USB DMA.
> > So restricting the usable DAM size to 4GB.
>
> Thanks, can you make this a proper patch submission along with a Fixes:
> tag that is:
>
> Fixes: 2013a4b684b6 ("arm64: dts: broadcom: clear the warnings caused by
> empty dma-ranges")

Yes, that would be helpful, though I would appreciate a better description
that explains what is actually going on: is it the device or the bus that
has the 32-bit limitation, and if it is indeed a bug in the device, why do
you pretend that this is a 64-bit device on a 32-bit bus instead (this
could also use a comment in the dts file)?

       Arnd