Re: [edk2-platforms: PATCH 1/1] Platform/RPi3: Accept "ethernet" or "ethernet0" aliases in device tree

["Pete Batard" <pete@akeo.ie>]

Just adding a comment for one item, that isn't directly relevant to what 
direction we should take with this patch, but that clarifies where we 
got our .dtb's from.

On 2019.07.23 12:00, Michael Brown wrote:
> On 23/07/2019 11:34, Leif Lindholm wrote:
>> On Fri, Jul 19, 2019 at 06:29:07PM +0100, Michael Brown wrote:
>>> Older device trees tend to use the alias "ethernet".  Newer device
>>> trees tend to use "ethernet0" since older versions of U-Boot would
>>> skip aliases that do not include an index number.  See, for example,
>>> Linux kernel commit 10b6c0c ("ARM: dts: bcm2835: add index to the
>>> ethernet alias") and U-Boot commit f8e57c6 ("fdt_support: Fixup
>>> 'ethernet' aliases not ending in digits").
>>>
>>> Accept either "ethernet" or "ethernet0" as being the alias to the node
>>> for which the MAC address should be updated.
>>
>> Why is this patch useful?
>> I understand the problem, but we include the .dtb from our own
>> edk2-non-osi tree. And it seems that device tree already provides an
>> alias to support both:
>> https://github.com/tianocore/edk2-non-osi/blob/master/Platform/RaspberryPi/RPi3/DeviceTree/bcm2710-rpi-3-b.dts 
>>
>>
>> Would it be more useful to warn loudly if "ethernet" isn't present?
>> (And just *replace* ethernet[0] with ethernet below.)
> 
> The device tree can also be provided by the VC4 firmware, e.g. with a 
> config.txt containing e.g.
> 
>    device_tree_address=0x10000
>    device_tree_end=0x20000
>    device_tree=bcm2710-rpi-3-b-plus.dtb
> 
> It is also possible to omit the explicit "device_tree=..." and have just
> 
>    device_tree_address=0x10000
>    device_tree_end=0x20000
> 
> This configuration will cause the VC4 firmware to automatically load the 
> appropriate device tree file.  I have tested that this allows me to boot 
> from a 3B or 3B+ using a single SD card image that contains all of the 
> .dtb files from
> 
>    https://github.com/raspberrypi/firmware/tree/master/boot
> 
> These "official" raspberrypi-firmware .dtb files are built from the 
> stock Linux kernel .dts files, and contain only "ethernet0".

Note that the .dtb's we use for this platform (in edk2-non-osi) were 
actually picked up from the URL above, then decompiled to produce a .dts 
which was then edited to fix a couple issues, as per:
https://github.com/tianocore/edk2-non-osi/blob/master/Platform/RaspberryPi/RPi3/DeviceTree/bcm2710-rpi-3-b-plus.dts#L6-L15

Most notably, unless you change
   compatible = "brcm,bcm2708-usb";
to
   compatible = "brcm,bcm2835-usb";
in the usb@7e980000 section you will find your USB keyboard may not work 
during a Linux install (Tested with both the Ubuntu 18.04 and Debian 10 
installers).

Now, I am also aware that the Raspberry Pi Foundation has updated its 
official .dtb's for the Pi 3 with the release of the Pi 4, and I have 
some plans to send a patch to also update our Device Tree accordingly at 
some stage. For the record, I've been testing these updated official 
versions last week and confirmed that the keyboard issue was still present.

Regards,

/Pete

> To address your specific questions:
> 
>  > Why is this patch useful?
> 
> It allows us to boot using the "official" .dtb files without any 
> unexpected behaviour.
> 
> This in turn allows us to boot with the VC4 firmware automatically 
> selecting the appropriate .dtb file for the hardware.  This is extremely 
> useful when trying to provide a single SD card image that will work on a 
> wide range of hardware.
> 
>  > Would it be more useful to warn loudly if "ethernet" isn't present?
>  > (And just *replace* ethernet[0] with ethernet below.)
> 
> This would also solve the problem.  I would find it mildly surprising 
> behaviour if I were debugging around it, since the "official" .dtb files 
> have moved in the other direction (going from "ethernet" to 
> "ethernet0"), but I would not expect it to break anything.
> 
> Another option would be to have UpdateMacAddress() ensure that both 
> "ethernet" and "ethernet0" aliases exist.
> 
> I am happy to work up a new version of the patch: just let me know which 
> option you prefer.
> 
> Many thanks,
> 
> Michael