RE: [RFC PATCH v2 2/6] bus/cdx: add the cdx bus driver

Gupta, Nipun
2022-08-29T04:49:32Z

[AMD Official Use Only - General]

> -----Original Message-----
> From: Jason Gunthorpe <jgg@nvidia.com>
> Sent: Friday, August 26, 2022 5:38 AM
> To: Robin Murphy <robin.murphy@arm.com>
> Cc: Saravana Kannan <saravanak@google.com>; Greg KH
> <gregkh@linuxfoundation.org>; Gupta, Nipun <Nipun.Gupta@amd.com>;
> robh+dt@kernel.org; krzysztof.kozlowski+dt@linaro.org; rafael@kernel.org;
> eric.auger@redhat.com; alex.williamson@redhat.com; cohuck@redhat.com;
> Gupta, Puneet (DCG-ENG) <puneet.gupta@amd.com>;
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> <nikhil.agarwal@amd.com>; Simek, Michal <michal.simek@amd.com>; git
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> Subject: Re: [RFC PATCH v2 2/6] bus/cdx: add the cdx bus driver
>
> [CAUTION: External Email]
>
> On Thu, Aug 25, 2022 at 08:57:49PM +0100, Robin Murphy wrote:
>
> > To my mind, it would definitely help to understand if this is a *real*
> > discoverable bus in hardware, i.e. does one have to configure one's device
> > with some sort of CDX wrapper at FPGA synthesis time, that then physically
> > communicates with some sort of CDX controller to identify itself once
> > loaded; or is it "discoverable" in the sense that there's some firmware on
> > an MCU controlling what gets loaded into the FPGA, and software can query
> > that and get back whatever precompiled DTB fragment came bundled with the
> > bitstream, i.e. it's really more like fpga-mgr in a fancy hat?
>
> So much of the IP that you might want to put in a FPGA needs DT, I
> don't thing a simplistic AMBA like discoverable thing would be that
> interesting.
>
> Think about things like FPGA GPIOs being configured as SPI/I2C, then
> describing the board config of SPI/I2C busses, setting up PCI bridges,
> flash storage controllers and all sorts of other typically embedded
> stuff that really relies on DT these days.
>
> It would be nice if Xilinx could explain more about what environment
> this is targetting. Is it Zynq-like stuff?

This solution is not targeted for GPIO/SPI or I2C like devices which rely on
DT, but would have PCI like network/storage devices. It is not targeted for
Zynq platform. I have added more details on other mail. Please refer to
that mail.

Thanks,
Nipun

>
> Jason