onboard wireless on rpi4

[Mark Millard]

On 2020-Sep-6, at 11:36, greg at unrelenting.technology wrote:

September 6, 2020 9:20 PM, "Mark Millard via freebsd-arm" <freebsd-arm at freebsd.org> wrote:
> 
>> On 2020-Sep-6, at 08:20, Robert Crowston via freebsd-arm <freebsd-arm at freebsd.org> wrote:
>> 
>>> That's interesting: OpenBSD is allowing only the lowest 1 GB of memory for DMA; the documentation I
>>> obtained suggests the first 3 GB should be accessible. I am experimenting with this new lower
>>> bound.
>> 
>> https://rpi4-uefi.dev/tag/netbsd reports:
>> 
>> QUOTE
>> NetBSD also is the only OS today to fully support ACPI _DMA descriptors for describing DMA
>> translations/constraints. This is very important for supporting Pi and Pi-like platforms via
>> straight-up ACPI and without platform DMA quirks.
>> END QUOTE
> 
> That would be https://reviews.freebsd.org/D25219 for us.. not "full support" though because our bus dma tags are way too weak and inflexible, much worse than NetBSD's :(
> 
> The RPi ACPI tables declare a 3GB limit for XHCI, and a 1GB limit for some other devices.
> 
> Namely, devices described by
> https://github.com/tianocore/edk2-platforms/blob/master/Platform/RaspberryPi/AcpiTables/GpuDevs.asl

It is not clear to me if the Greg vs. Robert developments in
this area are:

A) conflicting? (Use at most one of the two.)
B) compatible but independent?
C) compatible with one based on also using the other?

It sounds like Robert may be going the direction of using
the minimum of what is learned from what the ACPI tables
report as supportable in the hardware --and so may be using
a global 1 GiB limit for each PCIe device, including the
XHCI device.

===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)