Date:   Fri, 26 Aug 2022 19:35:12 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     Frank Li <frank.li@....com>
Cc:     Rob Herring <robh@...nel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "kw@...ux.com" <kw@...ux.com>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        Peng Fan <peng.fan@....com>,
        Aisheng Dong <aisheng.dong@....com>,
        "jdmason@...zu.us" <jdmason@...zu.us>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        dl-linux-imx <linux-imx@....com>,
        "kishon@...com" <kishon@...com>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "ntb@...ts.linux.dev" <ntb@...ts.linux.dev>,
        "lznuaa@...il.com" <lznuaa@...il.com>
Subject: Re: [EXT] Re: [PATCH v7 3/4] dt-bindings: irqchip: imx mu work as msi controller

On Thu, 25 Aug 2022 22:42:38 +0100,
Frank Li <frank.li@....com> wrote:
> 
> 
> 
> > -----Original Message-----
> > From: Rob Herring <robh@...nel.org>
> > Sent: Thursday, August 25, 2022 4:22 PM
> > To: Frank Li <frank.li@....com>
> > Cc: maz@...nel.org; tglx@...utronix.de; krzysztof.kozlowski+dt@...aro.org;
> > shawnguo@...nel.org; s.hauer@...gutronix.de; kw@...ux.com;
> > bhelgaas@...gle.com; linux-kernel@...r.kernel.org;
> > devicetree@...r.kernel.org; linux-arm-kernel@...ts.infradead.org; linux-
> > pci@...r.kernel.org; Peng Fan <peng.fan@....com>; Aisheng Dong
> > <aisheng.dong@....com>; jdmason@...zu.us; kernel@...gutronix.de;
> > festevam@...il.com; dl-linux-imx <linux-imx@....com>; kishon@...com;
> > lorenzo.pieralisi@....com; ntb@...ts.linux.dev; lznuaa@...il.com
> > Subject: [EXT] Re: [PATCH v7 3/4] dt-bindings: irqchip: imx mu work as msi
> > controller
> > 
> > Caution: EXT Email
> > 
> > On Mon, Aug 22, 2022 at 10:51:29AM -0500, Frank Li wrote:
> > > I.MX mu support generate irq by write a register. Provide msi controller
> > > support so other driver such as PCI EP can use it by standard msi
> > > interface as doorbell.
> > >
> > > Signed-off-by: Frank Li <Frank.Li@....com>
> > > ---
> > >  .../interrupt-controller/fsl,mu-msi.yaml      | 98 +++++++++++++++++++
> > >  1 file changed, 98 insertions(+)
> > >  create mode 100644 Documentation/devicetree/bindings/interrupt-
> > controller/fsl,mu-msi.yaml
> > >
> > > diff --git a/Documentation/devicetree/bindings/interrupt-controller/fsl,mu-
> > msi.yaml b/Documentation/devicetree/bindings/interrupt-controller/fsl,mu-
> > msi.yaml
> > > new file mode 100644
> > > index 0000000000000..ac07b138e24c0
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/interrupt-controller/fsl,mu-
> > msi.yaml
> > > @@ -0,0 +1,98 @@
> > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > +%YAML 1.2
> > > +---
> > > +$id:
> > https://eur01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fdevicet
> > ree.org%2Fschemas%2Finterrupt-controller%2Ffsl%2Cmu-
> > msi.yaml%23&amp;data=05%7C01%7CFrank.Li%40nxp.com%7Cbff8f186128d
> > 44209f4108da86dfc975%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0
> > %7C637970592959950791%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLj
> > AwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%
> > 7C%7C&amp;sdata=DHCOhmaJAhwb8Gl%2FEbPj32B6lR2zcIvyMY%2BTuPACb
> > zI%3D&amp;reserved=0
> > > +$schema:
> > https://eur01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fdevicet
> > ree.org%2Fmeta-
> > schemas%2Fcore.yaml%23&amp;data=05%7C01%7CFrank.Li%40nxp.com%7
> > Cbff8f186128d44209f4108da86dfc975%7C686ea1d3bc2b4c6fa92cd99c5c3016
> > 35%7C0%7C0%7C637970592959950791%7CUnknown%7CTWFpbGZsb3d8eyJ
> > WIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%
> > 7C3000%7C%7C%7C&amp;sdata=J4znEXyHnMyQOssSUsoxE2Mlhe2qCDC%2F
> > 9WN6SKv69aM%3D&amp;reserved=0
> > > +
> > > +title: Freescale/NXP i.MX Messaging Unit (MU) work as msi controller
> > > +
> > > +maintainers:
> > > +  - Frank Li <Frank.Li@....com>
> > > +
> > > +description: |
> > > +  The Messaging Unit module enables two processors within the SoC to
> > > +  communicate and coordinate by passing messages (e.g. data, status
> > > +  and control) through the MU interface. The MU also provides the ability
> > > +  for one processor (A side) to signal the other processor (B side) using
> > > +  interrupts.
> > > +
> > > +  Because the MU manages the messaging between processors, the MU
> > uses
> > > +  different clocks (from each side of the different peripheral buses).
> > > +  Therefore, the MU must synchronize the accesses from one side to the
> > > +  other. The MU accomplishes synchronization using two sets of matching
> > > +  registers (Processor A-facing, Processor B-facing).
> > > +
> > > +  MU can work as msi interrupt controller to do doorbell
> > > +
> > > +allOf:
> > > +  - $ref: /schemas/interrupt-controller/msi-controller.yaml#
> > > +
> > > +properties:
> > > +  compatible:
> > > +    enum:
> > > +      - fsl,imx6sx-mu-msi
> > > +      - fsl,imx7ulp-mu-msi
> > > +      - fsl,imx8ulp-mu-msi
> > > +      - fsl,imx8ulp-mu-msi-s4
> > > +
> > > +  reg:
> > > +    items:
> > > +      - description: a side register base address
> > > +      - description: b side register base address
> > > +
> > > +  reg-names:
> > > +    items:
> > > +      - const: processor a-facing
> > > +      - const: processor b-facing
> > 
> > Isn't 'a' and 'b' sufficient to distinguish? Personally, doesn't really
> > look like a case that benefits from -names at all.
> > 
> > In any case, -names shouldn't have spaces.
> 
> I like "a" and "b".
> 
> But Marc Zyngier suggested use above name.
> https://www.spinics.net/lists/linux-pci/msg128783.html
> 
> @Marc Zyngier

And I stand by my initial request. "a" doesn't convey any sort of
useful information. Why not "I" and "II", while we're at it? Or
something even funkier?

	M.

-- 
Without deviation from the norm, progress is not possible.

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