From: Andreas Kemnade <andreas@kemnade.info>
To: Daniel Thompson <daniel.thompson@linaro.org>
Cc: lee.jones@linaro.org, jingoohan1@gmail.com,
jacek.anaszewski@gmail.com, pavel@ucw.cz, dmurphy@ti.com,
robh+dt@kernel.org, mark.rutland@arm.com,
b.zolnierkie@samsung.com, dri-devel@lists.freedesktop.org,
linux-leds@vger.kernel.org, devicetree@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-fbdev@vger.kernel.org,
"H. Nikolaus Schaller" <hns@goldelico.com>
Subject: Re: [PATCH 1/2] backlight: lm3630a: add an enable gpio for the HWEN pin
Date: Tue, 10 Sep 2019 21:06:48 +0200 [thread overview]
Message-ID: <20190910210648.3594912d@kemnade.info> (raw)
In-Reply-To: <20190910102156.vmprsjebmlphkv34@holly.lan>
[-- Attachment #1: Type: text/plain, Size: 1355 bytes --]
On Tue, 10 Sep 2019 11:21:56 +0100
Daniel Thompson <daniel.thompson@linaro.org> wrote:
[...]
> > > Is this needed?
> > >
> > > This is a remove path, not a power management path, and we have no idea
> > > what the original status of the pin was anyway?
> > >
> >
> > Looking at Ishdn on page 5 of the datasheet, switching it off everytime
> > possible seems not needed. We would need to call chip_init() everytime
> > we enable the gpio or live with default values.
> > Therefore I did decide to not put it into any power management path.
> > But switching it on and not switching it off feels so unbalanced.
>
> Either the power consumed by the controller when strings aren't lit up
> matters, in which case the driver should implement proper power
> management or it doesn't matter and changing the pin state isn't needed.
>
> I'm happy with either of the above but this looks like a third way,
> where eager users could hack in a bit of extra power management by
> forcing drivers to unbind.
>
I think I will take the simple way. I am quite sure that the power
consumption with HWEN on and leds off does not matter. If someone
later comes up and finds out that I misread the datasheet, things
are prepared to be improved.
At least the hardware can be properly described in the devicetree.
Regards,
Andreas
[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 833 bytes --]
WARNING: multiple messages have this Message-ID (diff)
From: Andreas Kemnade <andreas@kemnade.info>
To: Daniel Thompson <daniel.thompson@linaro.org>
Cc: lee.jones@linaro.org, jingoohan1@gmail.com,
jacek.anaszewski@gmail.com, pavel@ucw.cz, dmurphy@ti.com,
robh+dt@kernel.org, mark.rutland@arm.com,
b.zolnierkie@samsung.com, dri-devel@lists.freedesktop.org,
linux-leds@vger.kernel.org, devicetree@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-fbdev@vger.kernel.org,
"H. Nikolaus Schaller" <hns@goldelico.com>
Subject: Re: [PATCH 1/2] backlight: lm3630a: add an enable gpio for the HWEN pin
Date: Tue, 10 Sep 2019 19:06:48 +0000 [thread overview]
Message-ID: <20190910210648.3594912d@kemnade.info> (raw)
In-Reply-To: <20190910102156.vmprsjebmlphkv34@holly.lan>
[-- Attachment #1: Type: text/plain, Size: 1355 bytes --]
On Tue, 10 Sep 2019 11:21:56 +0100
Daniel Thompson <daniel.thompson@linaro.org> wrote:
[...]
> > > Is this needed?
> > >
> > > This is a remove path, not a power management path, and we have no idea
> > > what the original status of the pin was anyway?
> > >
> >
> > Looking at Ishdn on page 5 of the datasheet, switching it off everytime
> > possible seems not needed. We would need to call chip_init() everytime
> > we enable the gpio or live with default values.
> > Therefore I did decide to not put it into any power management path.
> > But switching it on and not switching it off feels so unbalanced.
>
> Either the power consumed by the controller when strings aren't lit up
> matters, in which case the driver should implement proper power
> management or it doesn't matter and changing the pin state isn't needed.
>
> I'm happy with either of the above but this looks like a third way,
> where eager users could hack in a bit of extra power management by
> forcing drivers to unbind.
>
I think I will take the simple way. I am quite sure that the power
consumption with HWEN on and leds off does not matter. If someone
later comes up and finds out that I misread the datasheet, things
are prepared to be improved.
At least the hardware can be properly described in the devicetree.
Regards,
Andreas
[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 833 bytes --]
next prev parent reply other threads:[~2019-09-10 19:07 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-08 20:37 [PATCH 0/2] backlight_lm3630a: add enable_gpios property Andreas Kemnade
2019-09-08 20:37 ` Andreas Kemnade
2019-09-08 20:37 ` [PATCH 1/2] backlight: lm3630a: add an enable gpio for the HWEN pin Andreas Kemnade
2019-09-08 20:37 ` Andreas Kemnade
2019-09-09 10:57 ` Daniel Thompson
2019-09-09 10:57 ` Daniel Thompson
2019-09-09 20:13 ` Andreas Kemnade
2019-09-09 20:13 ` Andreas Kemnade
2019-09-10 10:21 ` Daniel Thompson
2019-09-10 10:21 ` Daniel Thompson
2019-09-10 19:06 ` Andreas Kemnade [this message]
2019-09-10 19:06 ` Andreas Kemnade
2019-09-15 16:52 ` Pavel Machek
2019-09-15 16:52 ` Pavel Machek
2019-09-15 17:34 ` Andreas Kemnade
2019-09-15 17:34 ` Andreas Kemnade
2019-09-08 20:37 ` [PATCH 2/2] dt-bindings: backlight: lm3630a: add enable_gpios Andreas Kemnade
2019-09-08 20:37 ` Andreas Kemnade
2019-09-09 10:59 ` Daniel Thompson
2019-09-09 10:59 ` Daniel Thompson
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=20190910210648.3594912d@kemnade.info \
--to=andreas@kemnade.info \
--cc=b.zolnierkie@samsung.com \
--cc=daniel.thompson@linaro.org \
--cc=devicetree@vger.kernel.org \
--cc=dmurphy@ti.com \
--cc=dri-devel@lists.freedesktop.org \
--cc=hns@goldelico.com \
--cc=jacek.anaszewski@gmail.com \
--cc=jingoohan1@gmail.com \
--cc=lee.jones@linaro.org \
--cc=linux-fbdev@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-leds@vger.kernel.org \
--cc=mark.rutland@arm.com \
--cc=pavel@ucw.cz \
--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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.