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From: Daniel Thompson <daniel.thompson@linaro.org>
To: Jean-Jacques Hiblot <jjhiblot@ti.com>
Cc: Pavel Machek <pavel@ucw.cz>,
	Jacek Anaszewski <jacek.anaszewski@gmail.com>,
	linux-leds@vger.kernel.org, linux-kernel@vger.kernel.org,
	dmurphy@ti.com, tomi.valkeinen@ti.com
Subject: Re: [PATCH v5 3/3] leds: Add control of the voltage/current regulator to the LED core
Date: Mon, 14 Oct 2019 13:38:49 +0100	[thread overview]
Message-ID: <20191014123849.fhvmqn7dyu6bminc@holly.lan> (raw)
In-Reply-To: <eb8c0df1-0d5b-11d0-9965-3192fa5675f3@ti.com>

On Mon, Oct 14, 2019 at 12:49:07PM +0200, Jean-Jacques Hiblot wrote:
> 
> On 13/10/2019 14:09, Pavel Machek wrote:
> > Hi!
> > 
> > > I must say I'm not a big fan of this change.
> > > It adds a bunch of code to the LED core and gives small
> > > functionality in a reward. It may also influence maximum
> > > software blinking rate, so I'd rather avoid calling
> > > regulator_enable/disable when timer trigger is set.
> > > 
> > > It will of course require more code.
> > > 
> > > Since AFAIR Pavel was original proponent of this change then
> > > I'd like to see his opinion before we move on to discussing
> > > possible improvements to this patch.
> > Was I?
> > 
> > Okay, this series looks quite confusing to me. First, 1/3 looks
> > "interesting" (would have to analyze it way more).
> > 
> > Second, 3/3... So we have a LED driver _and_ a regulator? So yes, the
> > chip driving a LED is usually ... voltage/current regulator. What is
> > second regulator doing there? Is that a common setup?
> 
> This is quite common with current-sink LED drivers.
> 
> The setup looks like this:
> 
> +-----------+
> |           |
> | Regulator |
> |           +------------------------+
> |           |                        |
> +-----------+                      __|__
>                                    \   /
>          +---------------------+    \ / led
>          |                     |     V
>          |    Led Driver       |   --+--
>          |                     |     |
>          |                     |     |
>          |                +----------+
>          |              \      |
>          |               \     |
>          |                +    |
>          |                |    |
>          +---------------------+
>                           |
>                        +--+--+
>                        ///////
> 
> 
> Only the regulator usually does not supply only one LED.

Given questions have been raised about the complexity of the change I
wondered whether, for a system with this topology, the regulator
could/should be enabled when the LED driver driver probes?


Daniel.

  reply	other threads:[~2019-10-14 12:38 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-23 10:20 [PATCH v5 0/3] leds: Add control of the voltage/current regulator to the LED core Jean-Jacques Hiblot
2019-09-23 10:20 ` [PATCH v5 1/3] led: make led_set_brightness_sync() use led_set_brightness_nosleep() Jean-Jacques Hiblot
2019-09-23 10:20 ` [PATCH v5 2/3] dt-bindings: leds: document the "power-supply" property Jean-Jacques Hiblot
2019-09-23 10:20 ` [PATCH v5 3/3] leds: Add control of the voltage/current regulator to the LED core Jean-Jacques Hiblot
2019-09-24 18:58   ` Jacek Anaszewski
2019-09-25  8:41     ` Jean-Jacques Hiblot
2019-10-13 12:09     ` Pavel Machek
2019-10-13 16:40       ` Jacek Anaszewski
2019-10-14 10:49       ` Jean-Jacques Hiblot
2019-10-14 12:38         ` Daniel Thompson [this message]
2019-10-14 18:48           ` Jacek Anaszewski
2019-10-16  8:13             ` Jean-Jacques Hiblot
2019-10-17 19:05               ` Jacek Anaszewski

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