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Fri, 30 May 2025 16:41:06 -0700 (PDT) From: Florian Fainelli To: bcm-kernel-feedback-list@broadcom.com, Andrea della Porta , Michael Turquette , Stephen Boyd , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Florian Fainelli , Lorenzo Pieralisi , Krzysztof Wilczynski , Manivannan Sadhasivam , Bjorn Helgaas , Linus Walleij , Catalin Marinas , Will Deacon , Bartosz Golaszewski , Derek Kiernan , Dragan Cvetic , Arnd Bergmann , Greg Kroah-Hartman , Saravana Kannan , linux-clk@vger.kernel.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, linux-gpio@vger.kernel.org, Masahiro Yamada , Stefan Wahren , Herve Codina , Luca Ceresoli , Thomas Petazzoni , Andrew Lunn , Phil Elwell , Dave Stevenson , kernel-list@raspberrypi.com, Matthias Brugger Cc: Florian Fainelli Subject: Re: [PATCH v12 07/13] misc: rp1: RaspberryPi RP1 misc driver Date: Fri, 30 May 2025 16:41:06 -0700 Message-ID: <20250530234106.465777-1-florian.fainelli@broadcom.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250529135052.28398-7-andrea.porta@suse.com> References: <20250529135052.28398-7-andrea.porta@suse.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250530_164108_215156_7F2A5AF3 X-CRM114-Status: GOOD ( 23.06 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: Florian Fainelli On Thu, 29 May 2025 15:50:44 +0200, Andrea della Porta wrote: > The RaspberryPi RP1 is a PCI multi function device containing > peripherals ranging from Ethernet to USB controller, I2C, SPI > and others. > > Implement a bare minimum driver to operate the RP1, leveraging > actual OF based driver implementations for the on-board peripherals > by loading a devicetree overlay during driver probe if the RP1 > node is not already present in the DT. > > The peripherals are accessed by mapping MMIO registers starting > from PCI BAR1 region. > > With the overlay approach we can achieve more generic and agnostic > approach to managing this chipset, being that it is a PCI endpoint > and could possibly be reused in other hw implementations. The > presented approach is also used by Bootlin's Microchip LAN966x > patchset (see link) as well, for a similar chipset. > In this case, the inclusion tree for the DT overlay is as follow > (the arrow points to the includer): > > rp1-pci.dtso <---- rp1-common.dtsi > > On the other hand, to ensure compatibility with downstream, this > driver can also work with a DT already comprising the RP1 node, so > the dynamically loaded overlay will not be used if the DT is already > fully defined. > > The reason why this driver is contained in drivers/misc has > been paved by Bootlin's LAN966X driver, which first used the > overlay approach to implement non discoverable peripherals behind a > PCI bus. For RP1, the same arguments apply: it's not used as an SoC > since the driver code is not running on-chip and is not like an MFD > since it does not really need all the MFD infrastructure (shared regs, > etc.). So, for this particular use, misc has been proposed and deemed > as a good choice. For further details about that please check the links. > > This driver is heavily based on downstream code from RaspberryPi > Foundation, and the original author is Phil Elwell. > > Link: https://datasheets.raspberrypi.com/rp1/rp1-peripherals.pdf > Link: https://lore.kernel.org/all/20240612140208.GC1504919@google.com/ > Link: https://lore.kernel.org/all/83f7fa09-d0e6-4f36-a27d-cee08979be2a@app.fastmail.com/ > Link: https://lore.kernel.org/all/2024081356-mutable-everyday-6f9d@gregkh/ > Link: https://lore.kernel.org/all/20240808154658.247873-1-herve.codina@bootlin.com/ > > Signed-off-by: Andrea della Porta > Acked-by: Bjorn Helgaas # quirks.c, pci_ids.h > Acked-by: Greg Kroah-Hartman > --- Applied to https://github.com/Broadcom/stblinux/commits/drivers/next, thanks! -- Florian