From mboxrd@z Thu Jan 1 00:00:00 1970 From: Enric Balletbo Serra Subject: Re: [PATCH v6 1/5] pwm-backlight: enable/disable the PWM before/after LCD enable toggle. Date: Mon, 26 Mar 2018 16:40:21 +0200 Message-ID: References: <20180326095213.18362-1-enric.balletbo@collabora.com> <20180326104205.GA12425@amd> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: In-Reply-To: <20180326104205.GA12425@amd> Sender: linux-kernel-owner@vger.kernel.org To: Pavel Machek Cc: Enric Balletbo i Serra , Lee Jones , Daniel Thompson , Jingoo Han , Rob Herring , Heiko Stuebner , Thierry Reding , Bartlomiej Zolnierkiewicz , Richard Purdie , Jacek Anaszewski , Linux PWM List , linux-fbdev@vger.kernel.org, linux-kernel , Guenter Roeck , "open list:ARM/Rockchip SoC..." , linux-leds@vger.kernel.org, "devicetree@vger.kernel.org" , kernel@collabora.com List-Id: devicetree@vger.kernel.org Hi Pavel, 2018-03-26 12:42 GMT+02:00 Pavel Machek : > On Mon 2018-03-26 11:52:09, Enric Balletbo i Serra wrote: >> Before this patch the enable signal was set before the PWM signal and >> vice-versa on power off. This sequence is wrong, at least, it is on >> the different panels datasheets that I checked, so I inverted the sequence >> to follow the specs. >> >> For reference the following panels have the mentioned sequence: >> - N133HSE-EA1 (Innolux) >> - N116BGE (Innolux) >> - N156BGE-L21 (Innolux) >> - B101EAN0 (Auo) >> - B101AW03 (Auo) >> - LTN101NT05 (Samsung) >> - CLAA101WA01A (Chunghwa) > > Ok, but this changes behaviour for other panels, too. Are you sure you > are not breaking one of those? I can't say that I am 100% sure because I didn't find all the datasheets of all the panels supported in the kernel. But all the datasheets I checked specifies this sequence as valid. In general I think that doesn't really matter, but I know that at least the B116XTN02 panel requires enable first the PWM, wait 10ms and then enable BL_EN to avoid garbage. So the other way around is not valid for this panel. That's the reason for this patchset. If anyone knows a panel that says the contrary, please let me know and I'll try to rework the patches to satisfy both requirements. Regards, Enric > Pavel > > -- > (english) http://www.livejournal.com/~pavelmachek > (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html