linux-gpio.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Linus Walleij <linus.walleij@linaro.org>
To: Michal Simek <michal.simek@xilinx.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
	Sai Krishna Potthuri <lakshmi.sai.krishna.potthuri@xilinx.com>
Subject: Re: DT overlay applied via pinctrl description
Date: Mon, 1 Mar 2021 10:19:04 +0100	[thread overview]
Message-ID: <CACRpkdZEYqPU6Zr+a6fivZiz-hKx6-KVdYVR7j--y+k2KXZaPw@mail.gmail.com> (raw)
In-Reply-To: <63d610ba-5f63-2be1-6215-f44bd88d94d2@xilinx.com>

On Tue, Feb 16, 2021 at 4:35 PM Michal Simek <michal.simek@xilinx.com> wrote:

> I have a question about expectations when pinctrl setting is applied. In
> DTS all nodes are described in the order available in DT.
>
> uart-default {
>         mux {
>                 ...
>         };
>
>         conf {
>                 ...
>         };
> };
>
> I don't know if this standard description or not. I definitely see other
> pinctrl drivers which are using different structure.
>
> Anyway when overlay is applied the order has changed to
> uart-default {
>         conf {
>                 ...
>         };
>
>         mux {
>                 ...
>         };
> };
>
> which is causing issue because pin is configured first via conf node
> before it is requested via mux. This is something what firmware is
> checking and error out.

As Frank says the DT ordering has no semantic meaning, it is essentially
a functional language, describes object relations not sequences.

The Linux kernel applies the mux and conf in that order because of how
the code is implemented (this order also makes a lot of sense for the
hardware). I would recommend to trace the execution of an overlay
being applied and try to find the reason conf goes before mux and fix
the bug there. I think it is a bug in how pinctrl handles DT overlays.

Yours,
Linus Walleij

  parent reply	other threads:[~2021-03-01  9:19 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-16 15:35 DT overlay applied via pinctrl description Michal Simek
2021-02-17  5:33 ` Frank Rowand
2021-03-01  9:19 ` Linus Walleij [this message]
2021-03-01  9:31   ` Michal Simek
2021-03-01 14:13     ` Linus Walleij
2021-03-01 15:04       ` Michal Simek

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=CACRpkdZEYqPU6Zr+a6fivZiz-hKx6-KVdYVR7j--y+k2KXZaPw@mail.gmail.com \
    --to=linus.walleij@linaro.org \
    --cc=lakshmi.sai.krishna.potthuri@xilinx.com \
    --cc=linux-gpio@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=michal.simek@xilinx.com \
    /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).