linux-kernel - Re: [PATCH 0/4] Fix RP1 DeviceTree hierarchy and drop overlay support

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Message-ID: <20251219152526.GA3333129-robh@kernel.org>
Date: Fri, 19 Dec 2025 09:25:26 -0600
From: Rob Herring <robh@...nel.org>
To: Andrea della Porta <andrea.porta@...e.com>
Cc: 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>,
	Bjorn Helgaas <bhelgaas@...gle.com>, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org, linux-pci@...r.kernel.org,
	iivanov@...e.de, svarbanov@...e.de, mbrugger@...e.com,
	Phil Elwell <phil@...pberrypi.com>
Subject: Re: [PATCH 0/4] Fix RP1 DeviceTree hierarchy and drop overlay support

On Thu, Dec 18, 2025 at 08:09:05PM +0100, Andrea della Porta wrote:
> The current RP1 implementation is plagued by several issues, as follows:
> 
> - the node name for RP1 is too specific and should be generic instead
>   (see [1]).
> 
> - the fully defined DTS has its PCI hierarchy wrongly described. There
>   should be a PCI root port between the root complex and the endpoint
>   (see [1]).
> 
> - since CONFIG_PCI_DYNAMIC_OF_NODES can be dropped in the future
>   becoming an automatically enabled feature, it would be wise to not
>   depend on it (see [2]).
> 
> - overlay support has led to a lot of confusion. It's not really usable 
>   right now and users are not even used to it (see [3]).
> 
> This patch aims at solving the aforementioned problems by amending the
> PCI topology as follows:
> 
>   ...
>   pcie@...0120000 {
>     ...
> 
>     pci@0,0 {
>       device_type = "pci";
>       reg = <0x00 0x00 0x00 0x00 0x00>;
>       ...
> 
>       dev@0,0 {
>         compatible = "pci1de4,1";
>         reg = <0x10000 0x00 0x00 0x00 0x00>;
>         ...
> 
>         pci-ep-bus@1 {
>           compatible = "simple-bus";
>           ...
> 
>           /* peripherals child nodes */
>         }; 
>       }; 
>     }; 
>   }; 
> 
> The reg property is important since it permits the binding the OF
> device_node structure to the pci_dev, encoding the BDF in the upper
> portion of the address.
> 
> This patch also drops the overlay support in favor of the fully
> described DT while streamlining it as a result.
> 
> Links:
> [1] - https://lore.kernel.org/all/aTvz_OeVnciiqATz@apocalypse/
> [2] - https://lore.kernel.org/all/CAL_JsqJUzB71QdMcxJtNZ7raoPcK+SfTh7EVzGmk=syo8xLKQw@mail.gmail.com/
> [3] - https://lore.kernel.org/all/CAL_JsqJUzB71QdMcxJtNZ7raoPcK+SfTh7EVzGmk=syo8xLKQw@mail.gmail.com/
> 
> Andrea della Porta (4):
>   dt-bindings: misc: pci1de4,1: add required reg property for endpoint
>   misc: rp1: drop overlay support
>   arm64: dts: broadcom: bcm2712: fix RP1 endpoint PCI topology
>   arm64: dts: broadcom: rp1: drop RP1 overlay

Thanks for doing this.

Reviewed-by: Rob Herring <robh@...nel.org>