Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753405AbbKPSoB (ORCPT ); Mon, 16 Nov 2015 13:44:01 -0500 Received: from mezzanine.sirena.org.uk ([106.187.55.193]:34753 "EHLO mezzanine.sirena.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751869AbbKPSn4 (ORCPT ); Mon, 16 Nov 2015 13:43:56 -0500 Date: Mon, 16 Nov 2015 18:42:38 +0000 From: Mark Brown To: Boris Brezillon Cc: Thierry Reding , linux-pwm@vger.kernel.org, Mike Turquette , Stephen Boyd , linux-clk@vger.kernel.org, Liam Girdwood , Kamil Debski , lm-sensors@lm-sensors.org, Jean Delvare , Guenter Roeck , Dmitry Torokhov , linux-input@vger.kernel.org, Bryan Wu , Richard Purdie , Jacek Anaszewski , linux-leds@vger.kernel.org, Maxime Ripard , Chen-Yu Tsai , linux-sunxi@googlegroups.com, Joachim Eastwood , Thomas Petazzoni , Heiko Stuebner , linux-rockchip@lists.infradead.org, Jingoo Han , Lee Jones , linux-fbdev@vger.kernel.org, Jean-Christophe Plagniol-Villard , Tomi Valkeinen , Robert Jarzmik , Alexandre Belloni , Julia Lawall , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Message-ID: <20151116184238.GJ31303@sirena.org.uk> References: <1447664207-24370-1-git-send-email-boris.brezillon@free-electrons.com> <1447664207-24370-10-git-send-email-boris.brezillon@free-electrons.com> <20151116105558.GB31303@sirena.org.uk> <20151116132359.39d84279@bbrezillon> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="EVh9lyqKgK19OcEf" Content-Disposition: inline In-Reply-To: <20151116132359.39d84279@bbrezillon> X-Cookie: Does the name Pavlov ring a bell? User-Agent: Mutt/1.5.24 (2015-08-30) X-SA-Exim-Connect-IP: 94.175.94.161 X-SA-Exim-Mail-From: broonie@sirena.org.uk Subject: Re: [PATCH v4 09/24] regulator: pwm: use pwm_get/set_default_xxx() helpers where appropriate X-SA-Exim-Version: 4.2.1 (built Mon, 26 Dec 2011 16:24:06 +0000) X-SA-Exim-Scanned: Yes (on mezzanine.sirena.org.uk) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2803 Lines: 63 --EVh9lyqKgK19OcEf Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Mon, Nov 16, 2015 at 01:23:59PM +0100, Boris Brezillon wrote: > Mark Brown wrote: > > On Mon, Nov 16, 2015 at 09:56:32AM +0100, Boris Brezillon wrote: > > > - pwm_reg_period = pwm_get_period(drvdata->pwm); > > > + pwm_reg_period = pwm_get_default_period(drvdata->pwm); > > It's not clear to me that we're not looking for the current period here > > or in the other use. Won't configuring based on a period other than the > > one that has been set give the wrong answer? > Hm, maybe that's naming problem. What I call the 'default' period here > is actually the period configured in your board file (using a PWM lookup > table) or your DT. This value represent the period requested by the PWM > user not a default value specified by the PWM chip driver. > The reason we're not using the 'current' period value is because it may > have been set by the bootloader, and may be inappropriate for our use > case (ie. the period may be to small to represent the different > voltages). > ITOH, we're using the current period value when calculating the current > voltage, because we want to get the correct voltage value, and the PWM > device may still use the configuration set by the bootloader (not the > default one specified in your board or DT files). > I hope this clarifies the differences between the current and default > period, and why we should use the default value here. To be honest I'm still a bit confused here. When do we actually apply the default setting and why do we keep on having to constantly override it rather than doing this once at boot? It feels wrong to be using it every time we set anything. I'd expect it to be something we only need to do at probe time or which would automatically be handled by the PWM framework (but that'd have issues changing the state and potentially breaking things if done in an uncoordiated fashion). --EVh9lyqKgK19OcEf Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQEcBAEBCAAGBQJWSiOeAAoJECTWi3JdVIfQIdUH/1scRqSmMSZgRyJZIIZMQoDg QI1nBFfCeHoulxgsKhCVxriZUsJi0JgZ0mBZF9ca0Bna9Mug0uKkXm51T+8Kkh8f Di1+BXRuQ0G1VS/YnQf7HG9Pwx+oDFvThQV/mvbc9cd4Wp6XQteeaBVjIt3P0p2L Yc8+SNOQOTITyLT3i3zpfRC4xVcOpBsZLx5/4Dceq/teTnZ6PglWvg02Z+kmgsMx ly5upQb1ESXbVu0rcwTtEf+S+m2JjL82AjOrFGi5VupQa0CYBH022kG9nPBSUH4y IoolWK/VjIufMUc5QU6mO2zGWMrbIPyZpQiZEEmvMMzgqdZtPdbd+Y2dM7242VU= =YZof -----END PGP SIGNATURE----- --EVh9lyqKgK19OcEf-- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/