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[86.9.19.6]) by smtp.gmail.com with ESMTPSA id c17sm21653738wrc.60.2019.10.14.05.38.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Oct 2019 05:38:51 -0700 (PDT) Date: Mon, 14 Oct 2019 13:38:49 +0100 From: Daniel Thompson To: Jean-Jacques Hiblot Cc: Pavel Machek , Jacek Anaszewski , 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 Message-ID: <20191014123849.fhvmqn7dyu6bminc@holly.lan> References: <20190923102059.17818-1-jjhiblot@ti.com> <20190923102059.17818-4-jjhiblot@ti.com> <3e648fab-638f-4aa0-dda9-8ddba6562751@gmail.com> <20191013120937.GK5653@amd> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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.