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Subject: Re: [PATCH v5 3/3] leds: Add control of the voltage/current regulator
 to the LED core
To:     Pavel Machek <pavel@ucw.cz>,
        Jacek Anaszewski <jacek.anaszewski@gmail.com>
CC:     <daniel.thompson@linaro.org>, <linux-leds@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <dmurphy@ti.com>,
        <tomi.valkeinen@ti.com>
References: <20190923102059.17818-1-jjhiblot@ti.com>
 <20190923102059.17818-4-jjhiblot@ti.com>
 <3e648fab-638f-4aa0-dda9-8ddba6562751@gmail.com> <20191013120937.GK5653@amd>
From:   Jean-Jacques Hiblot <jjhiblot@ti.com>
Message-ID: <eb8c0df1-0d5b-11d0-9965-3192fa5675f3@ti.com>
Date:   Mon, 14 Oct 2019 12:49:07 +0200
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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.

JJ


>
> Best regards,
> 								Pavel
>