Re: [PATCH v11 07/13] misc: rp1: RaspberryPi RP1 misc driver

[Andrea della Porta <andrea.porta@suse.com>]

Hi Matthias,

On 15:24 Thu 29 May     , Matthias Brugger wrote:
> 
> 
> On 29/05/2025 14:43, 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 <andrea.porta@suse.com>
> > Acked-by: Bjorn Helgaas <bhelgaas@google.com>   # quirks.c, pci_ids.h
> 
> What changed in this patch so that you didn't include the Acked-by from Greg
> [1], or is this an oversight?

Nothing really, just an oversight. Thanks for spotting that out. I will resend V12
with it as I also notice that are some inconsistencies with mail Message-id, as a
result of subseqeunt invokation of git-format-patch from different branch.

Thanks,
Andrea

> 
> Regards,
> Matthias
> 
> [1] https://lore.kernel.org/linux-arm-kernel/2025042551-agency-boozy-dc3b@gregkh/
>