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Message-ID: <20210430221442.GA3970483@robh.at.kernel.org>
Date: Fri, 30 Apr 2021 17:14:42 -0500
From: Rob Herring <robh@...nel.org>
To: Ezequiel Garcia <ezequiel@...labora.com>
Cc: Benjamin Gaignard <benjamin.gaignard@...labora.com>,
joro@...tes.org, will@...nel.org, heiko@...ech.de,
xxm@...k-chips.com, iommu@...ts.linux-foundation.org,
devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org,
kernel@...labora.com, Kever Yang <kever.yang@...k-chips.com>
Subject: Re: [PATCH v2 1/4] dt-bindings: iommu: rockchip: Convert IOMMU to DT
schema
On Thu, Apr 22, 2021 at 02:16:53PM -0300, Ezequiel Garcia wrote:
> (Adding Kever)
>
> Hi Benjamin,
>
> Thanks a lot for working on this, it looks amazing. Together with the great work
> that Rockchip is doing, it seems RK3566/RK3568 will have decent support very soon.
>
> One comment here:
>
> On Thu, 2021-04-22 at 16:15 +0200, Benjamin Gaignard wrote:
> > Convert Rockchip IOMMU to DT schema
> >
> > Signed-off-by: Benjamin Gaignard <benjamin.gaignard@...labora.com>
> > ---
> > version 2:
> > - Change maintainer
> > - Change reg maxItems
> > - Change interrupt maxItems
> >
> > .../bindings/iommu/rockchip,iommu.txt | 38 ---------
> > .../bindings/iommu/rockchip,iommu.yaml | 79 +++++++++++++++++++
> > 2 files changed, 79 insertions(+), 38 deletions(-)
> > delete mode 100644 Documentation/devicetree/bindings/iommu/rockchip,iommu.txt
> > create mode 100644 Documentation/devicetree/bindings/iommu/rockchip,iommu.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/iommu/rockchip,iommu.txt b/Documentation/devicetree/bindings/iommu/rockchip,iommu.txt
> > deleted file mode 100644
> > index 6ecefea1c6f9..000000000000
> > --- a/Documentation/devicetree/bindings/iommu/rockchip,iommu.txt
> > +++ /dev/null
> > @@ -1,38 +0,0 @@
> > -Rockchip IOMMU
> > -==============
> > -
> > -A Rockchip DRM iommu translates io virtual addresses to physical addresses for
> > -its master device. Each slave device is bound to a single master device, and
> > -shares its clocks, power domain and irq.
> > -
> > -Required properties:
> > -- compatible : Should be "rockchip,iommu"
> > -- reg : Address space for the configuration registers
> > -- interrupts : Interrupt specifier for the IOMMU instance
> > -- interrupt-names : Interrupt name for the IOMMU instance
> > -- #iommu-cells : Should be <0>. This indicates the iommu is a
> > - "single-master" device, and needs no additional information
> > - to associate with its master device. See:
> > - Documentation/devicetree/bindings/iommu/iommu.txt
> > -- clocks : A list of clocks required for the IOMMU to be accessible by
> > - the host CPU.
> > -- clock-names : Should contain the following:
> > - "iface" - Main peripheral bus clock (PCLK/HCL) (required)
> > - "aclk" - AXI bus clock (required)
> > -
> > -Optional properties:
> > -- rockchip,disable-mmu-reset : Don't use the mmu reset operation.
> > - Some mmu instances may produce unexpected results
> > - when the reset operation is used.
> > -
> > -Example:
> > -
> > - vopl_mmu: iommu@...40300 {
> > - compatible = "rockchip,iommu";
> > - reg = <0xff940300 0x100>;
> > - interrupts = <GIC_SPI 16 IRQ_TYPE_LEVEL_HIGH>;
> > - interrupt-names = "vopl_mmu";
> > - clocks = <&cru ACLK_VOP1>, <&cru HCLK_VOP1>;
> > - clock-names = "aclk", "iface";
> > - #iommu-cells = <0>;
> > - };
> > diff --git a/Documentation/devicetree/bindings/iommu/rockchip,iommu.yaml b/Documentation/devicetree/bindings/iommu/rockchip,iommu.yaml
> > new file mode 100644
> > index 000000000000..0db208cf724a
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/iommu/rockchip,iommu.yaml
> > @@ -0,0 +1,79 @@
> > +# SPDX-License-Identifier: GPL-2.0-only
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/iommu/rockchip,iommu.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Rockchip IOMMU
> > +
> > +maintainers:
> > + - Heiko Stuebner <heiko@...ech.de>
> > +
> > +description: |+
> > + A Rockchip DRM iommu translates io virtual addresses to physical addresses for
> > + its master device. Each slave device is bound to a single master device and
> > + shares its clocks, power domain and irq.
> > +
> > + For information on assigning IOMMU controller to its peripheral devices,
> > + see generic IOMMU bindings.
> > +
> > +properties:
> > + compatible:
> > + const: rockchip,iommu
> > +
> > + reg:
> > + minItems: 1
> > + maxItems: 2
> > +
> > + interrupts:
> > + minItems: 1
> > + maxItems: 2
> > +
> > + interrupt-names:
> > + minItems: 1
> > + maxItems: 2
> > +
>
> AFAICS, the driver supports handling multiple MMUs, and there's one reg and
> interrupt cell for each MMU. IOW, there's no requirement that maxItems is 2.
>
> Is there any way we can describe that? Or maybe just allow a bigger maximum?
With #iommu-cells == 0, how would one distinguish which IOMMU is
associated with a device? IOW, is more that 1 really usable?
If you need more just pick a maxItems value that's either the most seen
or 'should be enough'TM. If the entries are just multiple instances of
the same thing, please note that here.
Rob
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