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From: Rob Herring <robh+dt@kernel.org>
To: Diana Craciun OSS <diana.craciun@oss.nxp.com>
Cc: devicetree@vger.kernel.org, Hanjun Guo <guohanjun@huawei.com>,
	Marc Zyngier <maz@kernel.org>, Will Deacon <will@kernel.org>,
	PCI <linux-pci@vger.kernel.org>,
	Sudeep Holla <sudeep.holla@arm.com>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Linux IOMMU <iommu@lists.linux-foundation.org>,
	linux-acpi@vger.kernel.org,
	Makarand Pawagi <makarand.pawagi@nxp.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Robin Murphy <robin.murphy@arm.com>,
	"moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE"
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 09/12] dt-bindings: arm: fsl: Add msi-map device-tree binding for fsl-mc bus
Date: Fri, 22 May 2020 08:08:36 -0600
Message-ID: <CAL_JsqKf+cq9Nhs+M8ihC-Ls24YH-WEofW8H4kkFPWMhZw=unA@mail.gmail.com> (raw)
In-Reply-To: <ee7a5c04-814e-215f-ec74-52c2f3b881d0@oss.nxp.com>

On Fri, May 22, 2020 at 3:57 AM Diana Craciun OSS
<diana.craciun@oss.nxp.com> wrote:
>
> On 5/22/2020 12:42 PM, Robin Murphy wrote:
> > On 2020-05-22 00:10, Rob Herring wrote:
> >> On Thu, May 21, 2020 at 7:00 AM Lorenzo Pieralisi
> >> <lorenzo.pieralisi@arm.com> wrote:
> >>>
> >>> From: Laurentiu Tudor <laurentiu.tudor@nxp.com>
> >>>
> >>> The existing bindings cannot be used to specify the relationship
> >>> between fsl-mc devices and GIC ITSes.
> >>>
> >>> Add a generic binding for mapping fsl-mc devices to GIC ITSes, using
> >>> msi-map property.
> >>>
> >>> Signed-off-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
> >>> Cc: Rob Herring <robh+dt@kernel.org>
> >>> ---
> >>>   .../devicetree/bindings/misc/fsl,qoriq-mc.txt | 30
> >>> +++++++++++++++++--
> >>>   1 file changed, 27 insertions(+), 3 deletions(-)
> >>>
> >>> diff --git a/Documentation/devicetree/bindings/misc/fsl,qoriq-mc.txt
> >>> b/Documentation/devicetree/bindings/misc/fsl,qoriq-mc.txt
> >>> index 9134e9bcca56..b0813b2d0493 100644
> >>> --- a/Documentation/devicetree/bindings/misc/fsl,qoriq-mc.txt
> >>> +++ b/Documentation/devicetree/bindings/misc/fsl,qoriq-mc.txt
> >>> @@ -18,9 +18,9 @@ same hardware "isolation context" and a 10-bit
> >>> value called an ICID
> >>>   the requester.
> >>>
> >>>   The generic 'iommus' property is insufficient to describe the
> >>> relationship
> >>> -between ICIDs and IOMMUs, so an iommu-map property is used to define
> >>> -the set of possible ICIDs under a root DPRC and how they map to
> >>> -an IOMMU.
> >>> +between ICIDs and IOMMUs, so the iommu-map and msi-map properties
> >>> are used
> >>> +to define the set of possible ICIDs under a root DPRC and how they
> >>> map to
> >>> +an IOMMU and a GIC ITS respectively.
> >>>
> >>>   For generic IOMMU bindings, see
> >>>   Documentation/devicetree/bindings/iommu/iommu.txt.
> >>> @@ -28,6 +28,9 @@ Documentation/devicetree/bindings/iommu/iommu.txt.
> >>>   For arm-smmu binding, see:
> >>>   Documentation/devicetree/bindings/iommu/arm,smmu.yaml.
> >>>
> >>> +For GICv3 and GIC ITS bindings, see:
> >>> +Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.yaml.
> >>>
> >>> +
> >>>   Required properties:
> >>>
> >>>       - compatible
> >>> @@ -119,6 +122,15 @@ Optional properties:
> >>>     associated with the listed IOMMU, with the iommu-specifier
> >>>     (i - icid-base + iommu-base).
> >>>
> >>> +- msi-map: Maps an ICID to a GIC ITS and associated iommu-specifier
> >>> +  data.
> >>> +
> >>> +  The property is an arbitrary number of tuples of
> >>> +  (icid-base,iommu,iommu-base,length).
> >>
> >> I'm confused because the example has GIC ITS phandle, not an IOMMU.
> >>
> >> What is an iommu-base?
> >
> > Right, I was already halfway through writing a reply to say that all
> > the copy-pasted "iommu" references here should be using the
> > terminology from the pci-msi.txt binding instead.
>
> Right, will change it.
>
> >
> >>> +
> >>> +  Any ICID in the interval [icid-base, icid-base + length) is
> >>> +  associated with the listed GIC ITS, with the iommu-specifier
> >>> +  (i - icid-base + iommu-base).
> >>>   Example:
> >>>
> >>>           smmu: iommu@5000000 {
> >>> @@ -128,6 +140,16 @@ Example:
> >>>                  ...
> >>>           };
> >>>
> >>> +       gic: interrupt-controller@6000000 {
> >>> +               compatible = "arm,gic-v3";
> >>> +               ...
> >>> +               its: gic-its@6020000 {
> >>> +                       compatible = "arm,gic-v3-its";
> >>> +                       msi-controller;
> >>> +                       ...
> >>> +               };
> >>> +       };
> >>> +
> >>>           fsl_mc: fsl-mc@80c000000 {
> >>>                   compatible = "fsl,qoriq-mc";
> >>>                   reg = <0x00000008 0x0c000000 0 0x40>,    /* MC
> >>> portal base */
> >>> @@ -135,6 +157,8 @@ Example:
> >>>                   msi-parent = <&its>;
> >
> > Side note: is it right to keep msi-parent here? It rather implies that
> > the MC itself has a 'native' Device ID rather than an ICID, which I
> > believe is not strictly true. Plus it's extra-confusing that it
> > doesn't specify an ID either way, since that makes it look like the
> > legacy PCI case that gets treated implicitly as an identity msi-map,
> > which makes no sense at all to combine with an actual msi-map.
>
> Before adding msi-map, the fsl-mc code assumed that ICID and streamID
> are equal and used msi-parent just to get the reference to the ITS node.
> Removing msi-parent will break the backward compatibility of the already
> existing systems. Maybe we should mention that this is legacy and not to
> be used for newer device trees.

If ids are 1:1, then the DT should use msi-parent. If there is
remapping, then use msi-map. A given system should use one or the
other. I suppose if some ids are 1:1 and the msi-map was added to add
additional support for ids not 1:1, then you could end up with both.
That's fine in dts files, but examples should reflect the 'right' way.

Rob
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  reply index

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-21 12:59 [PATCH 00/12] ACPI/OF: Upgrade MSI/IOMMU ID mapping APIs Lorenzo Pieralisi
2020-05-21 12:59 ` [PATCH 01/12] ACPI/IORT: Make iort_match_node_callback walk the ACPI namespace for NC Lorenzo Pieralisi
2020-05-21 12:59 ` [PATCH 02/12] ACPI/IORT: Make iort_get_device_domain IRQ domain agnostic Lorenzo Pieralisi
2020-05-21 19:56   ` Bjorn Helgaas
2020-05-21 12:59 ` [PATCH 03/12] ACPI/IORT: Make iort_msi_map_rid() PCI agnostic Lorenzo Pieralisi
2020-05-21 13:00 ` [PATCH 04/12] ACPI/IORT: Remove useless PCI bus walk Lorenzo Pieralisi
2020-05-21 13:00 ` [PATCH 05/12] ACPI/IORT: Add an input ID to acpi_dma_configure() Lorenzo Pieralisi
2020-05-21 13:00 ` [PATCH 06/12] of/iommu: Make of_map_rid() PCI agnostic Lorenzo Pieralisi
2020-05-21 22:47   ` Rob Herring
2020-05-21 13:00 ` [PATCH 07/12] of/device: Add input id to of_dma_configure() Lorenzo Pieralisi
2020-05-21 23:02   ` Rob Herring
2020-05-21 13:00 ` [PATCH 08/12] of/irq: make of_msi_map_get_device_domain() bus agnostic Lorenzo Pieralisi
2020-05-21 19:57   ` Bjorn Helgaas
2020-05-21 13:00 ` [PATCH 09/12] dt-bindings: arm: fsl: Add msi-map device-tree binding for fsl-mc bus Lorenzo Pieralisi
2020-05-21 23:10   ` Rob Herring
2020-05-22  9:42     ` Robin Murphy
2020-05-22  9:57       ` Diana Craciun OSS
2020-05-22 14:08         ` Rob Herring [this message]
2020-05-22 14:34           ` Robin Murphy
2020-05-22 14:02       ` Rob Herring
2020-05-22 15:38         ` Laurentiu Tudor
2020-05-21 13:00 ` [PATCH 10/12] of/irq: Make of_msi_map_rid() PCI bus agnostic Lorenzo Pieralisi
2020-05-21 23:17   ` Rob Herring
2020-05-21 13:00 ` [PATCH 11/12] bus/fsl-mc: Refactor the MSI domain creation in the DPRC driver Lorenzo Pieralisi
2020-05-21 13:00 ` [PATCH 12/12] bus: fsl-mc: Add ACPI support for fsl-mc Lorenzo Pieralisi
2020-05-21 15:03   ` Laurentiu Tudor
2020-05-22  5:32     ` Makarand Pawagi
2020-05-22  9:53       ` Lorenzo Pieralisi

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