linux-kernel - Re: [PATCH 11/13] dtb: amd: Add PCIe SMMU device tree node

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Message-ID: <20160128142751.GA775@arm.com>
Date:	Thu, 28 Jan 2016 14:27:52 +0000
From:	Will Deacon <will.deacon@....com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Robin Murphy <robin.murphy@....com>,
	Mark Rutland <mark.rutland@....com>,
	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
	robh+dt@...nel.org, pawel.moll@....com,
	ijc+devicetree@...lion.org.uk, galak@...eaurora.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, arm@...nel.org,
	brijeshkumar.singh@....com, thomas.lendacky@....com,
	leo.duran@....com
Subject: Re: [PATCH 11/13] dtb: amd: Add PCIe SMMU device tree node

On Thu, Jan 28, 2016 at 03:17:33PM +0100, Arnd Bergmann wrote:
> On Thursday 28 January 2016 12:20:58 Robin Murphy wrote:
> > >
> > > Will, Robin, thoughts?
> > 
> > Any IDs specified here would only apply to DMA by the "platform device" 
> > side of the host controller itself (as would an equivalent "iommus" 
> > property on pcie0 once I finish the SMMUv2 generic binding support I'm 
> > working on). In terms of PCI devices, the "mmu-masters" property is 
> > overloaded such that only its existence matters, to identify that there 
> > _is_ a relationship between the SMMU and the PCI bus(es) behind that 
> > host controller.
> 
> I wasn't aware that this was actually still specified. I had hoped
> we were getting rid of mmu-masters before anyone actually started
> using it, but now I see it in ns2.dtsi and fsl-ls2080a.dtsi.
> 
> Does anyone know what happened to the plan to use the iommu DT binding
> for the ARM SMMU instead? Do we now have to support both ways indefinitely?

We always did -- Seattle used the mmu-masters binding before the generic
binding even existed. Robin has been working on patches to get of_xlate
up and running, but it got held up by Laurent's series which didn't end
up going anywhere.

Will