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

From: Rob Herring <robh@kernel.org>
To: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>,
	devicetree@vger.kernel.org, Dinh Nguyen <dinguyen@kernel.org>,
	Lee Jones <lee.jones@linaro.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Sudeep Holla <sudeep.holla@arm.com>,
	Michal Simek <michal.simek@xilinx.com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	Scott Branden <sbranden@broadcom.com>,
	Sylwester Nawrocki <s.nawrocki@samsung.com>,
	linux-samsung-soc@vger.kernel.org,
	Broadcom Kernel Team <bcm-kernel-feedback-list@broadcom.com>,
	linux-kernel@vger.kernel.org,
	Alim Akhtar <alim.akhtar@samsung.com>,
	Liviu Dudau <liviu.dudau@arm.com>, Ray Jui <rjui@broadcom.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 08/10] ARM: dts: exynos: use proper 'dma-channels/requests' properties
Date: Thu, 28 Apr 2022 08:33:13 -0500	[thread overview]
Message-ID: <YmqXmTau/YbZjrrn@robh.at.kernel.org> (raw)
In-Reply-To: <813bd5f2-38b6-9642-6993-94ad78f5c08a@linaro.org>

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