linux-kernel - Re: Raspberry Pi5 - RP1 driver

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Message-ID: <ba8cdf39-3ba3-4abc-98f5-d394d6867f95@gmx.net>
Date: Tue, 11 Jun 2024 21:05:24 +0200
From: Stefan Wahren <wahrenst@....net>
To: Lee Jones <lee@...nel.org>, Rob Herring <robh@...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>, devicetree@...r.kernel.org,
 linux-rpi-kernel@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>,
 linux-pci@...r.kernel.org, Dave Ertman <david.m.ertman@...el.com>,
 Lizhi Hou <lizhi.hou@....com>, clement.leger@...tlin.com,
 Jeremy Linton <jeremy.linton@....com>
Subject: Re: Raspberry Pi5 - RP1 driver - RFC

Hi Andrea,

i added Jeremy, because AFAIK he was deeply involved in ACPI
implementation of the RPi 4.

Am 11.06.24 um 17:39 schrieb Andrea della Porta:
> Hi,
> I'm on the verge of reworking the RP1 driver from downstream in order for it to be
> in good shape for upstream inclusion.
> RP1 is an MFD chipset that acts as a south-bridge PCIe endpoint sporting a pletora
> of subdevices (i.e.  Ethernet, USB host controller, I2C, PWM, etc.) whose registers
> are all reachable starting from an offset from the BAR address.
> The main point here is that while the RP1 as an endpoint itself is discoverable via
> usual PCI enumeraiton, the devices it contains are not discoverable and must be
> declared e.g. via the devicetree. This is an RFC about the correct approach to use
> in integrating the driver and registering the subdevices.
>
I cannot provide much input into the technical discussion, but i would
prefer an approach which works good with DT and ACPI.

Best regards
Stefan
>
> Link:
> - [1]: https://github.com/raspberrypi/linux/blob/rpi-6.6.y/arch/arm/boot/dts/broadcom/rp1.dtsi
> - [2]: https://github.com/raspberrypi/linux/blob/rpi-6.6.y/drivers/mfd/rp1.c
> - [3]: https://lpc.events/event/17/contributions/1421/attachments/1337/2680/LPC2023%20Non-discoverable%20devices%20in%20PCI.pdf
> - [4]: https://lore.kernel.org/lkml/20230419231155.GA899497-robh@kernel.org/t/
> - [5]: https://lore.kernel.org/lkml/Y862WTT03%2FJxXUG8@kroah.com/