On Thu, 11 Feb 2021 at 03:21, Rob Herring <r...@kernel.org> wrote: > > On Fri, Feb 5, 2021 at 1:21 AM Chunyan Zhang <zhang.l...@gmail.com> wrote: > > > > Hi Rob, > > > > On Fri, 5 Feb 2021 at 07:25, Rob Herring <r...@kernel.org> wrote: > > > > > > On Wed, Feb 03, 2021 at 05:07:26PM +0800, Chunyan Zhang wrote: > > > > From: Chunyan Zhang <chunyan.zh...@unisoc.com> > > > > > > > > This iommu module can be used by Unisoc's multimedia devices, such as > > > > display, Image codec(jpeg) and a few signal processors, including > > > > VSP(video), GSP(graphic), ISP(image), and CPP(camera pixel processor), > > > > etc. > > > > > > > > Signed-off-by: Chunyan Zhang <chunyan.zh...@unisoc.com> > > > > --- > > > > .../devicetree/bindings/iommu/sprd,iommu.yaml | 72 +++++++++++++++++++ > > > > 1 file changed, 72 insertions(+) > > > > create mode 100644 > > > > Documentation/devicetree/bindings/iommu/sprd,iommu.yaml > > > > > > > > diff --git a/Documentation/devicetree/bindings/iommu/sprd,iommu.yaml > > > > b/Documentation/devicetree/bindings/iommu/sprd,iommu.yaml > > > > new file mode 100644 > > > > index 000000000000..4fc99e81fa66 > > > > --- /dev/null > > > > +++ b/Documentation/devicetree/bindings/iommu/sprd,iommu.yaml > > > > @@ -0,0 +1,72 @@ > > > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) > > > > +# Copyright 2020 Unisoc Inc. > > > > +%YAML 1.2 > > > > +--- > > > > +$id: http://devicetree.org/schemas/iommu/sprd,iommu.yaml# > > > > +$schema: http://devicetree.org/meta-schemas/core.yaml# > > > > + > > > > +title: Unisoc IOMMU and Multi-media MMU > > > > + > > > > +maintainers: > > > > + - Chunyan Zhang <zhang.l...@gmail.com> > > > > + > > > > +properties: > > > > + compatible: > > > > + enum: > > > > + - sprd,iommu-v1 > > > > + > > > > + "#iommu-cells": > > > > + const: 0 > > > > + description: > > > > + Unisoc IOMMUs are all single-master IOMMU devices, therefore no > > > > + additional information needs to associate with its master device. > > > > + Please refer to the generic bindings document for more details, > > > > + Documentation/devicetree/bindings/iommu/iommu.txt > > > > + > > > > + reg: > > > > + maxItems: 1 > > > > + description: > > > > + Not required if 'sprd,iommu-regs' is defined. > > > > + > > > > + clocks: > > > > + description: > > > > + Reference to a gate clock phandle, since access to some of > > > > IOMMUs are > > > > + controlled by gate clock, but this is not required. > > > > + > > > > + sprd,iommu-regs: > > > > + $ref: /schemas/types.yaml#/definitions/phandle-array > > > > + description: > > > > + Reference to a syscon phandle plus 1 cell, the syscon defines the > > > > + register range used by the iommu and the media device, the cell > > > > + defines the offset for iommu registers. Since iommu module shares > > > > + the same register range with the media device which uses it. > > > > + > > > > +required: > > > > + - compatible > > > > + - "#iommu-cells" > > > > + > > > > +oneOf: > > > > + - required: > > > > + - reg > > > > + - required: > > > > + - sprd,iommu-regs > > > > + > > > > +additionalProperties: false > > > > + > > > > +examples: > > > > + - | > > > > + iommu_disp: iommu-disp { > > > > + compatible = "sprd,iommu-v1"; > > > > + sprd,iommu-regs = <&dpu_regs 0x800>; > > > > > > If the IOMMU is contained within another device, then it should just be > > > a child node of that device. > > > > Yes, actually IOMMU can be seen as a child of multimedia devices, I > > considered moving IOMMU under into multimedia device node, but > > multimedia devices need IOMMU when probe[1], so I dropped that idea. > > Don't design your binding around working-around linux issues. > > > And they share the same register base, e.g. > > > > + mm { > > + compatible = "simple-bus"; > > + #address-cells = <2>; > > + #size-cells = <2>; > > + ranges; > > + > > + dpu_regs: syscon@63000000 { > > Drop this node. > > > + compatible = "sprd,sc9863a-dpuregs", > > "syscon"; > > + reg = <0 0x63000000 0 0x1000>; > > + }; > > + > > + dpu: dpu@63000000 { > > + compatible = "sprd,sharkl3-dpu"; > > + sprd,disp-regs = <&dpu_regs>; > > reg = <0 0x63000000 0 0x800>; > > > + iommus = <&iommu_dispc>; > > + }; > > + > > + iommu_dispc: iommu@63000000 { > > + compatible = "sprd,iommu-v1"; > > + sprd,iommu-regs = <&dpu_regs 0x800>; > > reg = <0 0x63000800 0 0x800>;
Alright, considering you deprecate using syscon to map registers here, I will drop that. But that would cause the same physical address to be mapped two times at least. And this is not a single case, since there are a few media devices and their IOMMUs which all have this issue. Thanks, Chunyan > > > + #iommu-cells = <0>; > > Though given it seems there is only 1 client and this might really be > just 1 h/w block, you don't really need to use the iommu binding at > all. The DPU should be able to instantiate it's own IOMMU device. > There's other examples of this such as mali GPU though that is all one > driver, but that's a Linux implementation detail. > > Rob _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
