Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754540AbcJEQ4N (ORCPT ); Wed, 5 Oct 2016 12:56:13 -0400 Received: from mail.kmu-office.ch ([178.209.48.109]:52991 "EHLO mail.kmu-office.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752265AbcJEQ4L (ORCPT ); Wed, 5 Oct 2016 12:56:11 -0400 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Date: Wed, 05 Oct 2016 09:50:27 -0700 From: Stefan Agner To: Lukasz Majewski Cc: Bhuvanchandra DV , shawnguo@kernel.org, thierry.reding@gmail.com, mark.rutland@arm.com, linux-pwm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, robh+dt@kernel.org, kernel@pengutronix.de, fabio.estevam@nxp.com, linux-arm-kernel@lists.infradead.org, l.majewski@samsung.com Subject: Re: [PATCH v2 0/6] Support PWM polarity control In-Reply-To: <20161004094805.466ebc6d@jawa> References: <20161001101235.24598-1-bhuvanchandra.dv@toradex.com> <20161004094805.466ebc6d@jawa> Message-ID: User-Agent: Roundcube Webmail/1.1.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2926 Lines: 89 Hi Lukasz, On 2016-10-04 00:48, Lukasz Majewski wrote: > Dear Bhuvanchandra, > > Thank you for your effort to send those patches to ML. > >> Changes since v2: >> >> - Picked the stalled patchset[1] from Lothar Wassmann which adds the >> basic support for polarity control on imx-pwm driver and adds >> backward compatibility support for devices which does not have >> polarity control feature. >> >> Changes since Lothars v6: >> >> - Squash Lukasz patch[2]. >> >> [1] http://thread.gmane.org/gmane.linux.pwm/1621 >> [2] https://www.spinics.net/lists/arm-kernel/msg530818.html >> >> Bhuvanchandra DV (3): >> arm: dts: imx7: Update #pwm-cells for PWM polarity control >> arm: dts: imx7-colibri: Use pwm polarity control >> arm: dts: imx7-colibri: Use enable-gpios for BL_ON >> >> Lothar Wassmann (3): >> pwm: print error messages with pr_err() instead of pr_debug() >> pwm: core: make the PWM_POLARITY flag in DTB optional >> pwm: imx: support output polarity inversion > > For some reason this patchset works differently than the one developed > by Lothar. > > The difference is with the brightness level control. > > My brightness definition in DTS: > > pwms = <&pwm2 0 5000000 PWM_POLARITY_INVERTED>; > > brightness-levels = < 0 1 2 3 4 5 6 7 8 9 > > .. ............ > 250 251 252 253 254 255>; > default-brightness-level = <50>; > enable-gpios = <&gpio1 2 GPIO_ACTIVE_LOW>; > If you are using something else than i.MX 7 you also want to update the SoC level device tree, specifically change the pwm-cells property: #pwm-cells = <3>; > When I go to the backlight sysfs entry: > > cd /sys/devices/soc0/backlight/backlight/backlight > > It seems like the brightness level control is inverted - i.e. > 'echo 20 > brightness" makes picture on the screen very bright, and > 'echo 200 > brightness' makes the picture diminish. > > With my "internal" patches the situation is opposite (and I've checked it with > my HW connections). Just to check whether the driver actually applies the polarity you can add a #define DEBUG at the top of the driver (drivers/pwm/pwm-imx.c) and pass ignore_loglevel as kernel command line. This should give you "PWM supports output inversion" at startup and a "... polarity set to .." message whenever the polarity is set. -- Stefan > > Could you check on your setup if similar situation takes place? I mean > if the brightness control works as expected? > > Thanks in advance, > Łukasz Majewski > >> >> Documentation/devicetree/bindings/pwm/imx-pwm.txt | 6 +-- >> arch/arm/boot/dts/imx7-colibri.dtsi | 12 +++++- >> arch/arm/boot/dts/imx7s.dtsi | 8 ++-- >> drivers/pwm/core.c | 31 ++++++++------ >> drivers/pwm/pwm-imx.c | 51 >> +++++++++++++++++++++-- 5 files changed, 83 insertions(+), 25 >> deletions(-) >>