From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933138AbdC2WXH (ORCPT ); Wed, 29 Mar 2017 18:23:07 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:36371 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753985AbdC2WXG (ORCPT ); Wed, 29 Mar 2017 18:23:06 -0400 Date: Thu, 30 Mar 2017 00:23:02 +0200 From: Pavel Machek To: Bjorn Andersson Cc: Rob Herring , Richard Purdie , Jacek Anaszewski , linux-kernel@vger.kernel.org, linux-leds@vger.kernel.org, linux-arm-msm@vger.kernel.org, Mark Rutland , devicetree@vger.kernel.org Subject: Re: [PATCH 1/2] leds: Add driver for Qualcomm LPG Message-ID: <20170329222301.GB7977@amd> References: <20170323055435.29197-1-bjorn.andersson@linaro.org> <20170323203749.GB8563@amd> <20170329021734.afhqmfpmbcjyv7bu@rob-hp-laptop> <20170329190725.GN20094@minitux> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="zx4FCpZtqtKETZ7O" Content-Disposition: inline In-Reply-To: <20170329190725.GN20094@minitux> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --zx4FCpZtqtKETZ7O Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed 2017-03-29 12:07:25, Bjorn Andersson wrote: > On Tue 28 Mar 19:17 PDT 2017, Rob Herring wrote: >=20 > > On Thu, Mar 23, 2017 at 09:37:49PM +0100, Pavel Machek wrote: > > > Hi! > > >=20 > > > > The Light Pulse Generator (LPG) is a PWM-block found in a wide rang= e of > > > > PMICs from Qualcomm. It can operate on fixed parameters or based on= a > > > > lookup-table, altering the duty cycle over time - which provides the > > > > means for e.g. hardware assisted transitions of LED brightness. > > >=20 > > > Ok, this is not first hardware that supports something like this. We > > > have similar hardware that can do blinking on Nokia N900 -- please > > > take a look at leds-lp55*.c > >=20 > > And perhaps some alignment on the bindings too if the N900 has bindings. > >=20 >=20 > There is a binding for ti,lp55xx, but there's nothing I can reuse from > that binding...because it's completely different hardware. Agreed, if you drop the pattern stuff from the binding, at least for now.= =20 > > > And it would be really good to provide hardware abstraction. We really > > > don't want to have different userspace for LPG and for N900 and for > >=20 > > I'm interested in what this looks like as several AOSP platforms do=20 > > tri-color LEDs with custom sysfs extensions. >=20 > How to model RGB LEDs has been discussed many times before and I was > hoping for that discussion to come to some conclusion during the last 2 > years, but now I couldn't wait more - we need this driver for > db820c. If you want driver merged quickly, I believe the best way would be to leave out pattern support for now. We can merge the basic driver easily to 4.12. > With this driver, as with many existing, you will have 3 LEDs that you > set independently. >=20 > I did implement blinking by using the PWM straight off, so you can't set > brightness or synchronize the multiple channels. Perhaps this should be > changed to use the ramp generator. >=20 > To synchronize patterns I suggest that we extend the LUT binding to > describe groups and when any LPG trigger a restart of the pattern-walker > we trigger all that are grouped. >=20 > These two changes combined allows you to set brightness and blink with a > RGB-LED. >=20 >=20 > But I will have to dig up some hardware that uses the LPG for driving a > RGB-LED to be able to test this (and I do prefer that to be done with > some incremental patches at some later time, if acceptable). Incremental patches sound like a good idea, yes. I'd say that testing with actual RGB LED is not a requirement... as long as we design reasonable interface where the synchronizaction will be easy. Thanks and best regards, Pavel --=20 (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo= g.html --zx4FCpZtqtKETZ7O Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAljcM8UACgkQMOfwapXb+vKsCQCfXfhGqxNcKDaj3DECV7ukfIVE AUsAn1rOuukk88cS9/rwyzMPDmqZbDPm =F0EA -----END PGP SIGNATURE----- --zx4FCpZtqtKETZ7O--