linux-kernel - Re: [PATCH v11 0/6] PCI EP driver support MSI doorbell from host

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Message-ID: <86mtaj7hdw.wl-maz@kernel.org>
Date:   Wed, 28 Sep 2022 09:33:47 -0400
From:   Marc Zyngier <maz@...nel.org>
To:     Frank Li <Frank.Li@....com>
Cc:     tglx@...utronix.de, robh+dt@...nel.org,
        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@....com, aisheng.dong@....com, jdmason@...zu.us,
        kernel@...gutronix.de, festevam@...il.com, linux-imx@....com,
        kishon@...com, lorenzo.pieralisi@....com, ntb@...ts.linux.dev,
        lznuaa@...il.com, imx@...ts.linux.dev,
        manivannan.sadhasivam@...aro.org
Subject: Re: [PATCH v11 0/6] PCI EP driver support MSI doorbell from host

On Thu, 22 Sep 2022 12:12:40 -0400,
Frank Li <Frank.Li@....com> wrote:
> 
> 
> 
>                   ┌───────┐          ┌──────────┐
>                   │       │          │          │
> ┌─────────────┐   │       │          │ PCI Host │
> │ MSI         │◄┐ │       │          │          │
> │ Controller  │ │ │       │          │          │
> └─────────────┘ └─┼───────┼──────────┼─Bar0     │
>                   │ PCI   │          │ Bar1     │
>                   │ Func  │          │ Bar2     │
>                   │       │          │ Bar3     │
>                   │       │          │ Bar4     │
>                   │       ├─────────►│          │
>                   └───────┘          └──────────┘
> 
> Many PCI controllers provided Endpoint functions.
> Generally PCI endpoint is hardware, which is not running a rich OS,
> like linux.
> 
> But Linux also supports endpoint functions.  PCI Host write BAR<n> space
> like write to memory. The EP side can't know memory changed by the Host
> driver. 
> 
> PCI Spec has not defined a standard method to do that.  Only define
> MSI(x) to let EP notified RC status change. 

[...]

FWIW, I have queued the first 4 patches of this series into -next. If
there is a need for these patches to be pulled by another subsystem, I
have pushed out a stable branch at [1].

Thanks,

	M.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/log/?h=irq/fsl-mu-msi

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