[U-Boot] [U-Boot,6/6] Pine64: rename defconfig

[Alexander Graf]

On 15.05.16 14:49, André Przywara wrote:
> On 15/05/16 11:30, Hans de Goede wrote:
>> Hi,
>>
>> On 04-05-16 23:15, Andre Przywara wrote:
>>> Rename the defconfig file for the Pine64 from pine64_plus_defconfig to
>>> pine64_defconfig.
>>> The differences between the two versions (more RAM and a different
>>> Ethernet PHY) don't justify two board versions, so lets stick with the
>>> generic name and try to differentiate between the versions at runtime
>>> if this is needed later.
>>>
>>> Signed-off-by: Andre Przywara <andre.przywara at arm.com>
>>
>> So further down the thread there is some good discussion on
>> autodetection.
>>
>> I would prefer to keep the name as is (and matching the dts name)
>> for now until this is sorted out.
>>
>> As for the auto-detect discussion I'm all in favor of doing
>> auto-detect and having only one pine64 target in u-boot.
> 
> I fully agree. Hence I was proposing a more generic name (Pine64), as
> this is what people usually say, implying the plus variants of it as well.
> I found this several times when I was typing "make pine64_defconfig" and
> wondering why it didn't work. Typing pine64_plus_defconfig when everyone
> talks about those "Pine64" boards is just a bit counterintuitive - an
> also this pine64_plus config would cover the none-plus boards as well -
> which is just confusing.
> So my proposal was really about just a name change.
> But then again it's just a configuration name, so I don't have a strong
> opinion on this.
> 
>> But I'm against the idea to pass the u-boot dtb into the kernel.
>>
>> People will typically only install u-boot once and then get
>> kernel upgrades, including major version updates (Fedora does
>> this within a release, Debian on dist-upgrade) from their
>> distro, so we really want to stick with using the
>> dtb from the fdtdir entry in extlinux.conf
>>
>> The way this sofar works for sunxi boards is that the chosen
>> entry in extlinux.conf sets the fdtdir and then u-boot determines
>> the dtb name to use, since it knows which board it is booting
>> from.
>>
>> So when we do autodetection, the thing todo would be for the
>> autodetect code to update the fdtfile environment variable
>> to be one of: "sun50i-a64-pine64-plus", "sun50i-a64-pine64",
>> "sun50i-a64-pine64-other-variant" (*).
>>
>> And then upon booting u-boot will load $fdtdir/$fdtfile.
>>
>> Let me give one example where this will be beneficial over
>> using a u-boot supplied dtb:
>>
>> 1) User installs u-boot today, using boot0 and other closed
>> bits + say Fedora 24.
>> 2) In the future we add support for the csi camera
>> 3) User gets newer kernel from Fedora, this comes with
>> an updated "sun50i-a64-pine64-plus.dtb" which includes the
>> necessary changes to enable the csi interface, csi interface
>> just works.
>>
>> If u-boot where to supply the dtb, then the user would also
>> need to update u-boot, which is not part of the standard
>> yum / dnf / apt-get update process. Same for later enabling
>> hdmi output support, audio in/out, etc.
> 
> I understand and support all of these arguments (and hope you didn't
> spend too much time in writing this down ;-)
> 
> My idea was to have some kind of fallback DT in case there is none
> provided by the distribution. For many cases it would be good enough to
> just use U-Boot's DT, so I am looking for an easy way to set U-Boot's
> "externally-facing" DT addr to the internal one - something like "fdt
> internal" or having the internal DT address in a variable or just making

It's already in a variable today, so you can access (and copy) it if you
want :).

> it the default unless the user or boot script loads a custom one.

In the EFI case, we fall back to the internal fdt if we can't find a
matching file name on the boot media. That way users / distros can
provide newer dtb files while we still maintain compatibility with
distros / OSs that choose not to.

Other than those 2 points, I fully agree with you :). We should try to
provide a "known good" device tree on all systems we care about, so that
an OS can just consume it. Whether it's the internal dt or an
additionally bundled dt is an implementation detail imho.


Alex