linux-kernel - Re: [PATCH 04/11] of: address: Preserve the flags portion on 1:1 dma-ranges mapping

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Message-ID: <Ztc2DadAnxLIYFj-@apocalypse>
Date: Tue, 3 Sep 2024 18:15:09 +0200
From: Andrea della Porta <andrea.porta@...e.com>
To: Rob Herring <robh@...nel.org>
Cc: Andrea della Porta <andrea.porta@...e.com>,
	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Derek Kiernan <derek.kiernan@....com>,
	Dragan Cvetic <dragan.cvetic@....com>,
	Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Nicolas Ferre <nicolas.ferre@...rochip.com>,
	Claudiu Beznea <claudiu.beznea@...on.dev>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Saravana Kannan <saravanak@...gle.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>, linux-clk@...r.kernel.org,
	devicetree@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-gpio@...r.kernel.org, netdev@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-arch@...r.kernel.org,
	Lee Jones <lee@...nel.org>, Andrew Lunn <andrew@...n.ch>,
	Stefan Wahren <wahrenst@....net>,
	Herve Codina <herve.codina@...tlin.com>,
	Luca Ceresoli <luca.ceresoli@...tlin.com>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH 04/11] of: address: Preserve the flags portion on 1:1
 dma-ranges mapping

Hi Rob,

On 14:37 Fri 30 Aug     , Rob Herring wrote:
> On Thu, Aug 29, 2024 at 11:26 AM Andrea della Porta
> <andrea.porta@...e.com> wrote:
> >
> > Hi Rob,
> >

...

> 
> I think simple-bus where you have it is fine. It is really 1 level up
> that needs to be specified. Basically something that's referenced from
> the specific PCI device's schema (e.g. the RP1 schema (which you are
> missing)).
> 
> That schema needs to roughly look like this:
> 
> properties:
>   "#address-cells":
>     const: 3
>   "#size-cells":
>     const: 2
>   ranges:
>     minItems: 1
>     maxItems: 6
>     items:
>       additionalItems: true
>       items:
>         - maximum: 5  # The BAR number
>         - const: 0
>         - const: 0
>         - # TODO: valid PCI memory flags
> 
> patternProperties:
>   "^bar-bus@[0-5]$":
>     type: object
>     additionalProperties: true
>     properties:
>       compatible:
>         const: simple-bus
>       ranges: true
>

Hmmm.. not sure how this is going to work. The PCI device (RP1) will
havei, at runtime, a compatible like this:

compatible = "pci1de4,1\0pciclass,0200000\0pciclass,0200";

that is basically generated automatically by the OF framework. So, in the
schema you proposed above, I can put something like:

properties:
  compatible:
    contains:
      pattern: '^pci1de4,1'

or maybe I could omit the compatible entirely, like in:

https://github.com/devicetree-org/dt-schema/blob/main/dtschema/schemas/pci/pci-iommu.yaml

that seems to refer to generic compatible values.
In both cases though, I don't see how these binding could work with
make dt_binding_check, since there's no compatible known at compile
time (for the first approach), or no compatible at all (the second
approach).
Is it intended only as a loose documentation?
Or are you proposing that for a future new bus (hence with a new, specific,
compatible) that could be described by the schema above?

Many thanks,
Andrea
 
> There were some discussions around interrupt handling that might also
> factor into this.
> 
> Rob