linux-kernel - Re: [PATCH 08/10] ARM: dts: exynos: use proper 'dma-channels/requests' properties

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Message-ID: <YmqXmTau/YbZjrrn@robh.at.kernel.org>
Date:   Thu, 28 Apr 2022 08:33:13 -0500
From:   Rob Herring <robh@...nel.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Marek Szyprowski <m.szyprowski@...sung.com>,
        devicetree@...r.kernel.org, Dinh Nguyen <dinguyen@...nel.org>,
        Lee Jones <lee.jones@...aro.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Michal Simek <michal.simek@...inx.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Scott Branden <sbranden@...adcom.com>,
        Sylwester Nawrocki <s.nawrocki@...sung.com>,
        linux-samsung-soc@...r.kernel.org,
        Broadcom Kernel Team <bcm-kernel-feedback-list@...adcom.com>,
        linux-kernel@...r.kernel.org,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Liviu Dudau <liviu.dudau@....com>, Ray Jui <rjui@...adcom.com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 08/10] ARM: dts: exynos: use proper
 'dma-channels/requests' properties

On Thu, Apr 28, 2022 at 12:09:02PM +0200, Krzysztof Kozlowski wrote:
> On 28/04/2022 12:05, Marek Szyprowski wrote:
> >>>>> I also don't see any code that would read those properties. IMHO they
> >>>>> should be simply removed at all, at least for the PL330 related nodes.
> >>>> In current Linux implementation they indeed are not used. Nothing parses
> >>>> them. However:
> >>>> 1. They describe (hopefully correct) the hardware.
> >>>> 2. They might be used by other implementations of pl330 driver.
> >>>>
> >>>> I would not remove them from existing sources, but indeed maybe there is
> >>>> no need to add for new files.
> >>> What's the point in having dt properties duplicating data that might be
> >>> read from the driver registers?
> >> Hm, indeed, there is no point in this. Since they are read from
> >> registers, what was the idea behind in commit 42cf20980cde?
> > 
> > #dma-cells is indeed required, but the rest seems to be the cargo-cult 
> > of some kind.
> 
> Rob,
> 
> Any guidance from your side? Is there any benefit in describing the
> hadrware (dma-channels/dma-requests) if the same value can be read from
> registers?

Drop the properties. They should only be an override if ever needed.

Rob