Re: [PATCH] iio: adc: xilinx: support all ARM platforms

[Jonathan Cameron <jic23@kernel.org>]

On Fri, 7 Jun 2019 13:32:11 -0600
Robert Hancock <hancock@sedsystems.ca> wrote:

> On 2019-06-07 1:17 p.m., Alexandru Ardelean wrote:
> > On Fri, Jun 7, 2019 at 10:33 AM Michal Simek <michal.simek@xilinx.com> wrote:  
> >>
> >> On 06. 06. 19 17:21, Robert Hancock wrote:  
> >>> On 2019-06-06 4:09 a.m., Ardelean, Alexandru wrote:  
> >>>> On Wed, 2019-06-05 at 15:07 -0600, Robert Hancock wrote:  
> >>>>> [External]
> >>>>>
> >>>>>
> >>>>> Since the XADC logic can be used with standalone Xilinx FPGAs, this driver
> >>>>> can potentially be used with various ARM platforms, not just Zynq.
> >>>>> Change the Zynq dependency to ARM in the list of supported platforms
> >>>>> in the Kconfig dependencies for this driver.  
> >>>>
> >>>> To my knowledge, there are 3 FPGA platforms with ARM supported in Linux.
> >>>> And symbols are ARCH_ZYNQ, ARCH_ZYNQMP & ARCH_SOCFPGA.
> >>>> For these ARM + FPGA SoCs, it is usually preferred to list the supported/tested ARM + FPGA platforms in Kconfig.
> >>>>
> >>>> I am curious: are you using something that isn't in the above list?  
> >>>
> >>> Yes, we are using the XADC on a Kintex-7 FPGA through a PCIe to AXI
> >>> bridge using an iMX6D platform - not an integrated ARM+FPGA.
> >>>  
> > 
> > In that case, it would be a bit more interesting to do a depends on
> > PCIE_XILINX, or whichever is the Kconfig symbol for the PCIe-to-AXI
> > bridge.
> > 
> > And there are some benefits to that, the major being that you can also
> > support other ARCHs as well (x86, ppc, mips, etc).  
> 
> There isn't a kernel driver for that PCIe-AXI bridge - it doesn't really
> do much very interesting on its own, it just acts as a regular PCIe
> endpoint and has build-time settings to map AXI memory to PCIe BARs and
> host memory into AXI memory space. You have to build your own logic to
> do things like map interrupts from the AXI side onto MSI interrupts from
> the bridge.
> 
> It kind of seems like the easiest solution would be to just delete the
> platform restriction entirely for this driver, as I really don't see
> anything platform specific in there. Would anyone object to that?

Sounds good to me.

Jonathan

> 
> > 
> > Naturally, if using a different PCIe-to-AXI bridge controller (other
> > than Xilinx's), it would be an idea to use that Kconfig symbol.
> >   
> >>> Using such an approach this driver could potentially be used on just
> >>> about any platform, but I didn't want to open it up too much for now in
> >>> case of some compile issues.  
> >>
> >> 0day system should answer this for you.
> >>
> >> M  
>