From: Tomi Valkeinen <tomi.valkeinen-l0cyMroinI0@public.gmane.org>
To: Thierry Reding
<thierry.reding-RM9K5IK7kjKj5M59NBduVrNAH6kLmebB@public.gmane.org>
Cc: Sascha Hauer <s.hauer-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>,
Alex Courbot <acourbot-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>,
Stephen Warren <swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>,
Simon Glass <sjg-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>,
Grant Likely
<grant.likely-s3s/WqlpOiPyB63q8FvJNQ@public.gmane.org>,
Rob Herring <rob.herring-bsGFqQB8/DxBDgjK7y7TUQ@public.gmane.org>,
Mark Brown
<broonie-yzvPICuk2AATkU/dhu1WVueM+bqZidxxQQ4Iyu8u01E@public.gmane.org>,
Anton Vorontsov <cbou-JGs/UdohzUI@public.gmane.org>,
David Woodhouse <dwmw2-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>,
Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>,
Leela Krishna Amudala
<l.krishna-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>,
"linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
"linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
"linux-fbdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-fbdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
"devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org"
<devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org>,
"linux-pm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-pm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
"linux-doc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-doc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
Subject: Re: [PATCH v6 1/4] Runtime Interpreted Power Sequences
Date: Thu, 13 Sep 2012 11:00:18 +0300 [thread overview]
Message-ID: <1347523218.3014.4.camel@deskari> (raw)
In-Reply-To: <20120913072920.GA11459-RM9K5IK7kjIQXX3q8xo1gnVAuStQJXxyR5q1nwbD4aMs9pC9oP6+/A@public.gmane.org>
[-- Attachment #1: Type: text/plain, Size: 3955 bytes --]
On Thu, 2012-09-13 at 09:29 +0200, Thierry Reding wrote:
> On Thu, Sep 13, 2012 at 10:03:27AM +0300, Tomi Valkeinen wrote:
> > On Thu, 2012-09-13 at 09:00 +0200, Sascha Hauer wrote:
> > > On Thu, Sep 13, 2012 at 09:54:09AM +0300, Tomi Valkeinen wrote:
> > > > On Thu, 2012-09-13 at 15:36 +0900, Alex Courbot wrote:
> > > > > On Thursday 13 September 2012 14:22:57 Tomi Valkeinen wrote:
> > > > >
> > > > > > However, I fear these board specific things may be quite a bit anything,
> > > > > > so it may well be pwm, gpios and regulators are not enough for them. For
> > > > > > example, there could be an FPGA on the board which requires some
> > > > > > configuration to accomplish the task at hand. It could be rather
> > > > > > difficult to handle it with a generic power sequence.
> > > > >
> > > > > Right. Note that this framework is supposed to be extended - I would like to
> > > > > at least add regulator voltage setting, and maybe even support for clocks and
> > > > > pinmux (but that might be out of place).
> > > >
> > > > Yes, that's one concern of mine... I already can imagine someone
> > > > suggesting adding conditionals to the power sequence data. Perhaps also
> > > > direct memory read/writes so you can twiddle registers directly. And so
> > > > on. Where's the limit what it should contain? Can we soon write full
> > > > drivers with the DT data? =)
> > >
> > > I have this concern aswell, that's why I'm sceptical about this patch
> > > set. But what are the alternatives? Adding power code to the drivers and
> > > thus adding board specific code to them is backwards.
> >
> > As was pointed out in earlier posts in this thread, these are almost
> > always device specific, not board specific.
> >
> > Do you have examples of board specific power sequences or such?
>
> It is true that most (perhaps all) power sequences can be associated
> with a specific device, but if we go and implement drivers for these
> kinds of devices we will probably end up with loads of variations of
> the same scheme.
>
> Lets take display panels as an example. One of the devices that we build
> has gone through two generations so far and both are slightly different
> in how they control the panel backlight: one has an external backlight
> controller, the other has the display controller built into the panel.
> However, from the board's perspective the control of the backlight
> doesn't change, because both devices get the same inputs (an enable pin
> and a PWM) that map to the same pins on the SoC.
We had something a bit similar in Nokia. First versions had an
"independent" backlight controlled via pwm. Later versions had a
backlight that is controlled by the panel IP, so it was changed by
sending DSI commands to the panel.
> This may not be a very good example because the timing isn't relevant,
> but the basic point is still valid: if we provide a driver for both
> panel devices, the code will be exactly the same. So we end up having to
> refactor to avoid code duplication and use the same driver for a number
> of backlight/panel combinations. Which in itself isn't very bad, but it
> also means that we'll probably get to see a large number of "generic"
> drivers which aren't very generic after all.
>
> Another problem, which also applies to the case of power-sequences, is
> that often the panel and backlight are not the same device. So you could
> have the same panel with any number of different backlight controllers
> or vice-versa any number of different panels with the same backlight
> controller.
Yes, I think the backlight and the panel should be considered separate
devices. Just like, say, a touch screen and a panel may happen to be in
the same display module, a backlight and a panel can be in the same
display module. They are still separate, independent things, although
they are, of course, used together.
Tomi
[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 836 bytes --]
next prev parent reply other threads:[~2012-09-13 8:00 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-12 9:57 [PATCH v6 0/4] Runtime Interpreted Power Sequences Alexandre Courbot
[not found] ` <1347443867-18868-1-git-send-email-acourbot-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
2012-09-12 9:57 ` [PATCH v6 1/4] " Alexandre Courbot
2012-09-12 22:07 ` Stephen Warren
2012-09-13 6:02 ` Alex Courbot
2012-09-13 15:44 ` Stephen Warren
[not found] ` <1347443867-18868-2-git-send-email-acourbot-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
2012-09-13 5:45 ` Tomi Valkeinen
2012-09-13 6:08 ` Alex Courbot
2012-09-13 6:22 ` Tomi Valkeinen
2012-09-13 6:36 ` Alex Courbot
2012-09-13 6:54 ` Tomi Valkeinen
2012-09-13 7:00 ` Sascha Hauer
[not found] ` <20120913070012.GC6180-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
2012-09-13 7:03 ` Tomi Valkeinen
2012-09-13 7:18 ` Sascha Hauer
[not found] ` <20120913071829.GE6180-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
2012-09-13 7:27 ` Tomi Valkeinen
2012-09-13 7:21 ` Alex Courbot
2012-09-13 7:29 ` Thierry Reding
2012-09-13 7:50 ` Sascha Hauer
2012-09-13 8:21 ` Alex Courbot
2012-09-13 8:26 ` Thierry Reding
[not found] ` <20120913072920.GA11459-RM9K5IK7kjIQXX3q8xo1gnVAuStQJXxyR5q1nwbD4aMs9pC9oP6+/A@public.gmane.org>
2012-09-13 8:00 ` Tomi Valkeinen [this message]
2012-09-13 8:32 ` Thierry Reding
2012-09-13 7:08 ` Alex Courbot
2012-09-13 15:37 ` Stephen Warren
2012-09-13 8:09 ` Mark Brown
2012-09-12 9:57 ` [PATCH v6 3/4] tegra: dt: add label to tegra20's PWM Alexandre Courbot
2012-09-12 9:57 ` [PATCH v6 2/4] pwm_backlight: use power sequences Alexandre Courbot
2012-09-12 22:15 ` Stephen Warren
2012-09-12 9:57 ` [PATCH v6 4/4] tegra: ventana: add pwm backlight DT nodes Alexandre Courbot
[not found] ` <1347443867-18868-5-git-send-email-acourbot-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
2012-09-12 21:23 ` Stephen Warren
2012-09-12 21:27 ` [PATCH v6 0/4] Runtime Interpreted Power Sequences Stephen Warren
[not found] ` <5050FE28.2080502-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>
2012-09-12 21:33 ` Anton Vorontsov
2012-09-13 5:53 ` Alex Courbot
2012-09-13 5:50 ` Tomi Valkeinen
2012-09-13 6:23 ` Alex Courbot
2012-09-13 6:25 ` Mark Brown
2012-09-13 6:42 ` Alex Courbot
2012-09-13 7:19 ` Mark Brown
2012-09-13 7:26 ` Alex Courbot
2012-09-13 7:29 ` Mark Brown
2012-09-13 15:24 ` Stephen Warren
2012-09-19 3:01 ` Mark Brown
[not found] ` <5051FAC5.40501-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>
2012-10-03 8:24 ` Alex Courbot
[not found] ` <506BF62F.6040308-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
2012-10-03 15:30 ` Stephen Warren
2012-09-13 6:42 ` Tomi Valkeinen
2012-09-13 6:48 ` Tomi Valkeinen
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=1347523218.3014.4.camel@deskari \
--to=tomi.valkeinen-l0cymroini0@public.gmane.org \
--cc=acourbot-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org \
--cc=arnd-r2nGTMty4D4@public.gmane.org \
--cc=broonie-yzvPICuk2AATkU/dhu1WVueM+bqZidxxQQ4Iyu8u01E@public.gmane.org \
--cc=cbou-JGs/UdohzUI@public.gmane.org \
--cc=devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org \
--cc=dwmw2-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org \
--cc=grant.likely-s3s/WqlpOiPyB63q8FvJNQ@public.gmane.org \
--cc=l.krishna-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org \
--cc=linux-doc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
--cc=linux-fbdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
--cc=linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
--cc=linux-pm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
--cc=linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
--cc=rob.herring-bsGFqQB8/DxBDgjK7y7TUQ@public.gmane.org \
--cc=s.hauer-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org \
--cc=sjg-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org \
--cc=swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org \
--cc=thierry.reding-RM9K5IK7kjKj5M59NBduVrNAH6kLmebB@public.gmane.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).