[Gta04-owner] Updates for gta04 DTS file.

NeilBrown neilb at suse.de
Tue Jan 6 20:54:29 CET 2015

On Mon, 5 Jan 2015 23:02:32 +0100 "Dr. H. Nikolaus Schaller"
<hns at goldelico.com> wrote:

> Hi,
> Am 05.01.2015 um 21:01 schrieb NeilBrown <neilb at suse.de>:
> > On Sun, 4 Jan 2015 12:23:38 +0100 "Dr. H. Nikolaus Schaller"
> > <hns at goldelico.com> wrote:
> > 
> >> Hi Neil,
> >> 
> >> Am 03.01.2015 um 20:27 schrieb NeilBrown <neilb at suse.de>:
> >> 
> >>> 
> >>> Hi Marek, Nikolaus,
> >>> 
> >>> I'm wondering what your plans are for pushing more updates for the gta04 dts
> >>> file upstream?
> >> 
> >> The plan: as fast as we can with our small team. Rome wasn’t built in a day :)
> > 
> > Understood.  So I would like to help build Rome and am trying to find the
> > easiest way to collaborate on this.
> That is welcome.
> > 
> >> 
> >>> There are quite a few fixes that both of us have in our
> >>> different trees and I'm hoping they can go upstream soon.
> >> 
> >> Well, we could think about having one tree to avoid this situation...
> > 
> > We have one tree - Linus maintains it for us.  
> No, I see three trees:
> * Linus'
> * yours
> * gta04-kernel
> which are not in sync and both, the second and third, are almost independently developed and
> have the goal to get merged into Linus'. The question is how (by which collaboration model) things
> are synced.

There is a well established model.  Patches go from developer to maintainer to
Linus (possibly though intermediate maintainers).

> At the moment I think they are synced through Linus. I.e. the one who is faster in submitting and
> convincing Linus (and his submaintainers) wins. And the second one was waste of energy (because
> there was no discussion during development - just about the results).

Duplicated effort does not equate to wasted effort.  If two people work on
one thing then in the end, two people understand it.  That is better (for the
community) than only one.  Please be assured that if you get something
upstream which means that something I was working on is no longer needed, I
will not feel that my work has been wasted.  I will be happy that upstream
has improved.

Where do you suppose this "discussion during development" might happen?  As
I've said before I think the best place for discussion is on the lists
relevant to the specific subsystem. e.g. linux-mmc for mmc related things.
I try to remember to CC things here, but really there just aren't that many
kernel developers on this list, and we seem to be interested in quite
separate parts  of the kernel.

Certainly we could discuss changes to the dts file...

On that topic, I had a look through some of your changes.  I note that you
tried to add pinctrl settings for the hdq pin:

        hdq_pins: hdq_pins {
                pinctrl-single,pins = <
                        OMAP3_CORE1_IOPAD(0x21c4, PIN_OUTPUT_PULLDOWN | MUX_MODE0) /* i2c3_sda.hdq */

but that it didn't work.
I think the problem is that "0x21c4" should be "0x21c6".
0x21c4, bits 0-15 is i2c3_sda and gpio_185.
0x21c4, bits 16-31 is hdq_sio, various others, and gpio_170.
To get the top two bytes you add 2, so 0x21c6.

commit 4807b3a4b338c7d59fff61c0b75cace5d411f236
Author: H. Nikolaus Schaller <hns at goldelico.com>
Date:   Wed Oct 29 22:21:21 2014 +0100

    GTA04 DT: set default brightness of PWM backlight to 80%

                brightness-levels = <0 11 20 30 40 50 60 70 80 90 100>;
-               default-brightness-level = <10>;
+               default-brightness-level = <80>;

This is wrong.  The "brightness-levels" map an index (0-10 in this case) to
percent duty cycle.
The default-brightness-level is an index into the array of brightness-levels,
so 10 is the maximum value.

> Is such a competition approach efficient? Is this producing good solutions? I don’t know myself
> and would be interested in opinions of other gta04-owners how they would like to see the gta04
> kernel development been done: competitive or cooperatively?

I don't see our work as competitive.
I agree that it isn't particularly cooperative.  Partly that is because I
don't like the way you manage your kernel tree, and you don't want to
change.  Partly it is because we seem to be interested in quite different

To be honest, I'm quite happy working by myself.  I do what I can and then
present it to the upstream maintainer and any interested parties.  I
incorporate responses and hopefully ultimately get things included upstream.

If I find that there is someone else working in a similar area to me I would
certainly discuss issues with them, but for the most part that doesn't
happen.  I occasionally post here about what I have been working on in case
someone else is interested.  I hope others who might be working on code might
also post in case I or others are interested.

> > As soon as patches land there
> > they are equally available to everyone.
> which is too late for doing coordinated work upfront to shape what is being upstreamed…
> I mean: we (the gta04 users and project) should have only one tree where we
> develop things until they are mature to hand them over to Linus for maintaining.


I think we are working on different projects, you and I.

My project it "make the mainline kernel work on the GTA04".  This means
working with various parts of the kernel community to improve functionality
of mainline linux so that functionality is available to the GTA04.  It is
very important to have the discussion in the broader forums as that more
perspective and more expertise is available and so more general and well
rounded results can be obtained.

Your project seems to be "create a kernel that works well on the GTA04".
That leads you to think that the GTA04 community should be doing something.
To me that is a very small vision.  I'd rather think "the Linux kernel
community should be doing something".

To be honest, "we" the "gta04 project" have no hope at all of producing
something mature and ready to hand over to Linus.  We just don't have the
skills and the experience.  We *need* to regularly interact with relevant
parts of the broader community - to see ourselves as simply a part of that
community and not something separate - to have any hope of producing anything

> > 
> > 
> >> 
> >>> 
> >>> I have the following 11 patches which I could send upstream with your
> >>> Acked-by, or which I could send you to be forwarded to Tony, or which could
> >>> simply become irrelevant if you'll be sending your own patches upstream soon.
> >> 
> >> Marek as the DT maintainer should send them to lkml adding his ack and proper
> >> attribution of the original author(s).
> > 
> > OK, I'll send him the patches, though as your small team is apparently short
> > of time it might be easier for him to just Ack the patches and then I can
> > send them upstream - there is  plenty of precedent for maintainers not
> > actually handing the patches, just Acking them.
> Acking is the critical piece of work. Not formatting and sending patches. So your offer
> does not reduce significant work.

I'm offering to do all the non-critical bits so that you have time to focus
on that critical stuff.

> I understand your urgency but please give us time to do the quality checks your work
> deserves.
> > 
> >> 
> >>> 
> >>> I've included the list of patch titles and the combined diff below.  The
> >>> individual patches are in
> >>>  git://neil.brown.name/gta04 dts
> >>> or at
> >>>  http://git.neil.brown.name/?p=gta04.git;a=shortlog;h=refs/heads/dts
> >>> 
> >>> or I am happy to post them here.
> >> 
> >> So if easily possible please (re)format them as a patch-set against
> >> 
> >> http://git.goldelico.com/?p=gta04-kernel.git;a=shortlog;h=refs/heads/3.19-rc2
> >> 
> >> and submit here.
> > 
> > That doesn't make any sense.  Patches against your tree would not apply
> > upstream,
> Why not? We are based on top of upstream. Just some patches ahead. The 3-way
> git merge should resolve them.

"should" != "does".

I just tried.

If you were "based on top of upstream", then
  git log --follow v3.19-rc2.. arch/arm/boot/dts/omap3-gta04.dtsi

would show my just the changes you have made to that file against upstream.
It doesn't.  It also shows lots of things that are already upstream.  It
is very hard to see which of the ...

$ git log --follow --oneline  v3.19-rc2.. arch/arm/boot/dts/omap3-gta04.dtsi | wc -l

100 patches listed are still relevant and which have gone upstream and which
have been replaced by subsequent patches and ....

> > so Marek would not be able to send them upstream without
> > re-formatting them to apply to upstream.  So it would be a waste of
> > everyone's time.
> But how do you expect that we test the patches? Just from looking at them?

That is up to the maintainer.  Sometimes a visual inspection is all that is
required and all that is possible.

Generally a maintainer will have a tree in which they put patches that are
ready to go upstream.  Some maintainers will have several for different
levels of readiness.
This (or one of these) will normally be automatically included in linux-next
where it gets some basic integration (compile) testing.
The maintainer will normally test this tree before upstream submission, and
will expect developers to develop against this tree.
So for example my mmc patches are against the 'next' branch of 

which makes it easy for Ulf to apply and test them.

If Marek had such a tree I would certainly provide patches against that and
he would be able to test them.
Testing against a tree that differs significantly from mainline is
something that Linus has very explicitly said he doesn't like.  To some
extent we have to do that with the GTA04 as so much doesn't work, but it is
best to keep it to a minimum.

I think we are that the stage were you can boot a mainline kernel on the
GTA04, providing you have a serial console attached. So it would be possible
to test against a plain upstream kernel before submission.

But as I said, it is really up to the maintainer.  Different circumstances
suggest different compromises.


> > 
> > 
> >> 
> >>> 
> >>> Please let me know how you would like to proceed.
> >> 
> >> Marek will go through them and check if anything is missing/problematic and we
> >> will discuss here (if necessary). Finally he submits it upstream and we all will see
> >> what we get as a response.
> >> 
> >> I have only one diff in doubt (without cross-checking with code): the patch for mmc2
> >> appears to assume driver-features that are not yet in mainline. Or are these new
> >> features of 3.19-rc2?
> > 
> > I assume you are referring to the declaration of a second interrupt line
> > and the pinctrl settings?  This enables the SDIO card to interrupt the CPU.
> > 
> > Support for this went upstream in v3.17:
> > 
> > commit 2cd3a2a54656f9c480b1c7272fc07635d575841b
> > Author: Andreas Fenkart <afenkart at gmail.com>
> > Date:   Thu May 29 10:28:00 2014 +0200
> > 
> >    mmc: omap_hsmmc: Enable SDIO interrupt
> Ah, thanks. We have not noticed this nice sdio feature. There are so many changes in
> upstream hidden in tons of commit messages so that you don’t find all the gold nuggets…
> > 
> > 
> > 
> >> 
> >> What we have learned is that the policy by Tony (and others) is that they reject
> >> DT patches where the driver is not yet capable of using the attributes (and they
> >> expect a bindings document as well).
> > 
> > Of course.  I kept back all the patches which use features that aren't
> > upstream yet.
> > 
> > Thanks,
> > NeilBrown
> BR,
> Nikolaus

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