From: Linus Walleij <linus.walleij@linaro.org>
To: Jerome Brunet <jbrunet@baylibre.com>, Rob Herring <robh+dt@kernel.org>
Cc: Kevin Hilman <khilman@baylibre.com>,
"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
<devicetree@vger.kernel.org>,
"open list:ARM/Amlogic Meson..."
<linux-amlogic@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
Guillaume La Roque <glaroque@baylibre.com>
Subject: Re: [PATCH 0/2] pinctrl: meson: add g12a drive strength support
Date: Thu, 4 Apr 2019 10:41:04 +0700 [thread overview]
Message-ID: <CACRpkdYdRfm=OLmfzZeJEXpfOdnxg=YE+yAexHTh_-EePBtxaA@mail.gmail.com> (raw)
In-Reply-To: <20190314163725.7918-1-jbrunet@baylibre.com>
On Thu, Mar 14, 2019 at 11:37 PM Jerome Brunet <jbrunet@baylibre.com> wrote:
> Now the slightly annoying part :(
> The value achievable by the SoC are 0.5mA, 2.5mA, 3mA and 4mA and the DT property
> 'drive-strength' is expressed in mA.
>
> 1) Rounding down the value, we could be requesting a 0mA drive strength.
> That would look weird.
> 2) Rounding up, we can't distinguish between 2.5mA and 3mA
>
> To solve this issue in this in this v1, we chose to document that, on Amlogic,
> drive-strength is expressed in uA instead of mA.
> It works well and there is no impact on the other platforms but I'm not sure this
> is really OK with the DT rules ?
I want the DT people to say what they think about this.
> Linus, if this is not OK with you, here are 2 other options we are
> considering. We would be very interested to get your opinion on the matter:
>
> 1) instead the generic 'drive-strength' property, we could add an amlogic
> specific property, 'amlogic,drive-strength'. It would be expressed in uA
> and parsed in amlogic specific code.
> I think this option is kind of overkill. Expressing drive strength in uA is
> not really amlogic specific so it does not make much sense, but it would
> work ...
>
> 2) Add another generic property "drive-strength-uA". The change to do so
> would be minimal and could be benefit to other platforms later on.
I would go for 2).
But we really need input from bindings people on this.
Yours,
Linus Walleij
prev parent reply other threads:[~2019-04-04 3:41 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-14 16:37 [PATCH 0/2] pinctrl: meson: add g12a drive strength support Jerome Brunet
2019-03-14 16:37 ` [PATCH 1/2] dt-bindings: pinctrl: meson: Add drive-strength property Jerome Brunet
2019-03-31 6:40 ` Rob Herring
2019-03-31 7:04 ` Jerome Brunet
2019-04-04 3:42 ` Linus Walleij
2019-03-14 16:37 ` [PATCH 2/2] pinctrl: meson: add support of drive-strength Jerome Brunet
2019-03-18 13:12 ` Neil Armstrong
2019-03-25 9:44 ` [PATCH 0/2] pinctrl: meson: add g12a drive strength support Jerome Brunet
2019-04-04 3:41 ` Linus Walleij [this message]
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='CACRpkdYdRfm=OLmfzZeJEXpfOdnxg=YE+yAexHTh_-EePBtxaA@mail.gmail.com' \
--to=linus.walleij@linaro.org \
--cc=devicetree@vger.kernel.org \
--cc=glaroque@baylibre.com \
--cc=jbrunet@baylibre.com \
--cc=khilman@baylibre.com \
--cc=linux-amlogic@lists.infradead.org \
--cc=linux-gpio@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=robh+dt@kernel.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).