devicetree.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Maxime Ripard <maxime.ripard@bootlin.com>
To: "Rodrigo Exterckötter Tjäder" <rodrigo@tjader.xyz>
Cc: wens@csie.org, robh+dt@kernel.org, mark.rutland@arm.com,
	linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] arm64: dts: allwinner: Olimex A64-OLinuXino: enable eMMC.
Date: Tue, 2 Oct 2018 15:13:12 +0200	[thread overview]
Message-ID: <20181002131312.soqwybsohdifvso3@flea> (raw)
In-Reply-To: <CAG7TQgGS7DkLpNVYqfCD-9vMZkeY6r+L-5oXKWef3x-OVbqjtw@mail.gmail.com>

[-- Attachment #1: Type: text/plain, Size: 3670 bytes --]

On Sat, Sep 29, 2018 at 01:51:02PM -0300, Rodrigo Exterckötter Tjäder wrote:
> On Sat, Sep 29, 2018 at 12:47 PM Maxime Ripard
> <maxime.ripard@bootlin.com> wrote:
> >
> > On Thu, Sep 27, 2018 at 11:49:20AM -0300, Rodrigo Exterckötter Tjäder wrote:
> > > On Thu, Sep 27, 2018 at 5:17 AM Maxime Ripard <maxime.ripard@bootlin.com> wrote:
> > > >
> > > > On Tue, Sep 25, 2018 at 02:47:59PM -0300, Rodrigo Exterckötter Tjäder wrote:
> > > > > On Tue, Sep 25, 2018 at 6:01 AM Maxime Ripard <maxime.ripard@bootlin.com> wrote:
> > > > > > We can't really do that, unfortunately. If the device tree name was to
> > > > > > change for a given board, we'd break all the build systems, boot
> > > > > > scripts and distros out there.
> > > > >
> > > > > What if we keep the device tree for the version without WiFi and eMMC
> > > > > with the current name and create new device trees for the other two
> > > > > versions?
> > > >
> > > > Wifi and Bluetooth should be dealt with with overlays in this case,
> > > > and since the eMMC is already enabled, then there's nothing to do, I
> > > > guess.
> > >
> > > It's WiFi that is already enabled, not eMMC. Only one of the three
> > > variants has WiFi.
> >
> > Ah, right, sorry. In the board that doesn't have an emmc, are the pins
> > usable for something else?
> 
> I don't have the variant without eMMC nor could I find pictures of it.
> The schematics do mention that the A64 pins could be used to control
> NAND flash, but you'd have to solder that yourself.

Ok.

> > > We can't even remove a node from a device tree? Removing the WiFi node
> > > from the current tree would make it correspond to the variant with the
> > > least features.
> >
> > Not really. How pissed would you be if you were a user, had wifi
> > running on your board, you upgrade your kernel, and then it's just
> > gone? :)
> 
> That would suck, but what about someone who has the board with no wifi
> and problems start happening because the wifi is enabled on the device
> tree?

Did that happen or is it a theoretical issue?

> > > About device tree overlays, I read overlay-notes.txt, but I went
> > > looking for an example with "git grep /plugin/ arch" and it came
> > > empty. Is this approach not used for other boards?
> >
> > It is, it's simply not stored in the kernel, but through other third
> > party repos.
> 
> So that would mean that it's up to every distro to support the boards
> instead of relying on mainline support?

Distros would have to integrate it either way. One would need to
detect and / or ask for the board variant in order to load say the BT
stack, or to know if you want to boot from the eMMC or from the SD
card.

> > > Does the overlay approach make the device available at boot time? That
> > > is important for a storage device such as eMMC.
> > >
> > > I went with the separate dts approach because that's what I saw was
> > > done for other similar cases, like Pine64 and Pine64+, OLinuXino-LIME2
> > > and its variant with eMMC, among others.
> >
> > Yeah, but in all these cases, it was done from day one, not after the
> > facts.
> 
> For the LIME2 the dts for the emmc variant was commited two years
> after the base LIME2 dts.
> 
> What if instead of keeping the current dt for the least featureful
> model we keep it for the most featureful model and create new dts for
> the two less featureful models?

This is a different story though. The LIME2 eMMC variant was created
way after the original LIME2, with a separate name.

Maxime

-- 
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

  reply	other threads:[~2018-10-02 13:13 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-19 14:18 [PATCH 1/2] arm64: dts: allwinner: Olimex A64-OLinuXino: enable eMMC Rodrigo Exterckötter Tjäder
2018-09-21 14:28 ` Maxime Ripard
2018-09-21 14:54   ` Rodrigo Exterckötter Tjäder
2018-09-25  9:01     ` Maxime Ripard
2018-09-25 17:47       ` Rodrigo Exterckötter Tjäder
2018-09-27  8:17         ` Maxime Ripard
2018-09-27 14:49           ` Rodrigo Exterckötter Tjäder
2018-09-29 15:47             ` Maxime Ripard
2018-09-29 16:51               ` Rodrigo Exterckötter Tjäder
2018-10-02 13:13                 ` Maxime Ripard [this message]
2018-10-02 16:47                   ` Rodrigo Exterckötter Tjäder
2018-10-05 15:48                     ` Maxime Ripard
2018-11-15 14:46                       ` Rodrigo Exterckötter Tjäder

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20181002131312.soqwybsohdifvso3@flea \
    --to=maxime.ripard@bootlin.com \
    --cc=devicetree@vger.kernel.org \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mark.rutland@arm.com \
    --cc=robh+dt@kernel.org \
    --cc=rodrigo@tjader.xyz \
    --cc=wens@csie.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).