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

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Message-ID: <CAK8P3a1TViQopQNFE4+Dtac0v2CneGiy22WYu5BuYv8HX2r8Lg@mail.gmail.com>
Date:   Tue, 15 Dec 2020 16:49:10 +0100
From:   Arnd Bergmann <arnd@...nel.org>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Bharat Gooty <bharat.gooty@...adcom.com>,
        Ray Jui <ray.jui@...adcom.com>,
        devicetree <devicetree@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Scott Branden <sbranden@...adcom.com>,
        Ray Jui <rjui@...adcom.com>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        bcm-kernel-feedback-list <bcm-kernel-feedback-list@...adcom.com>,
        Zhen Lei <thunder.leizhen@...wei.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 1/2] arm64: dts: broadcom: clear the warnings caused by
 empty dma-ranges

On Tue, Dec 15, 2020 at 4:41 PM Florian Fainelli <f.fainelli@...il.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