Re: [PATCH] ARM: bcm2835: dt: Add a fall-back Raspberry Pi tree

On 01/25/2016 02:09 PM, Lubomir Rintel wrote:

On Mon, 2016-01-25 at 13:55 -0700, Stephen Warren wrote:

quoted

On 01/25/2016 01:39 PM, Lubomir Rintel wrote:

quoted

U-Boot falls back to "bcm2835-rpi-other.dtb" for boards of unknown
identification. Let's do a bare minimum for them so that they at leat
boot.

Signed-off-by: Lubomir Rintel <redacted>
---
   arch/arm/boot/dts/Makefile              | 1 +
   arch/arm/boot/dts/bcm2835-rpi-other.dts | 7 +++++++

This DT shouldn't ever be used, except when a new unidentified board
appears. In that case, I believe the correct solution is to add support
for that new board to U-Boot and the kernel, rather than add fall-backs.
Prior to that being done, a user can always copy whichever DT they want
into filename bcm2835-rpi-other.dts for temporary testing/development,
if they have reason to believe their new model is compatible with
something else. In general, I don't think we have any reason to believe
that even this new minimal DT is guaranteed to be compatible with any
possible future hardware, so it seems a little risky to ship this file
in anticipation.

Fair enough. It just frustrates me a bit that the chance of mainline
working on a new or even older RPi board is not as good as I'd like to.
I guess I could perhaps get a bit better at quickly submitting the
device tree instead of cheap hacks then.

By the way, I've seen you add an entry for the Zero board to U-Boot and
was thinking that you perhaps had a device tree for it? Do you plan to
include that one into mainline Linux, or do you keep your dts
elsewhere? Should I go ahead and submit one?

I'm not sure if I booted Linux on it. I probably did, and simply 
manually copied one of the other DTs (model A or A+ I would guess) to 
bcm2835-rpi-zero.dtb on my SD card to make it work.

Also, the Model B entries in U-Boot version table seems incorrect to me
(sent a separate message to U-Boot list, but it got caught in
moderation now). I'm wondering what's the authoritative source for the
version information? Did you get the version numbers from the actual
hardware or is some documentation available?

The information was derived from the various web pages listed in 
comments in board/raspberrypi/rpi/rpi.c. There may have been one or two 
entries contributed by other people; I don't know where that information 
came from. Most model numbers (for entries I added at least) are 
verified on real HW (yes, I have about 8 Pis.). I think I assigned the 
model strings/names myself in general, using names that seemed 
reasonably descriptive.

It would be nice if the Pi Foundation published a single 
up-to-date/complete definitive list, but I haven't seen such a thing; 
everyone seems to be reverse-engineering it based on seeing models in 
the wild or cribbing from bits of other GPIO-related SW projects:-(
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