From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexandre Belloni Subject: Re: [PATCH 2/2] rtc: pcf2127: add battery-low INTn generation Date: Wed, 3 Apr 2019 17:31:43 +0200 Message-ID: <20190403153143.GQ22216@piout.net> References: <1554303165-24813-1-git-send-email-f.suligoi@asem.it> <1554303165-24813-2-git-send-email-f.suligoi@asem.it> <20190403150824.GO22216@piout.net> <452a4cf1410a41c8b6f767ac6258482e@asem.it> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <452a4cf1410a41c8b6f767ac6258482e@asem.it> Sender: linux-kernel-owner@vger.kernel.org To: Flavio Suligoi Cc: Alessandro Zummo , Rob Herring , Mark Rutland , "linux-rtc@vger.kernel.org" , "devicetree@vger.kernel.org" , "linux-kernel@vger.kernel.org" List-Id: devicetree@vger.kernel.org On 03/04/2019 15:14:24+0000, Flavio Suligoi wrote: > Hi Alexandre, > > > On 03/04/2019 16:52:45+0200, Flavio Suligoi wrote: > > > The pcf2127 has an automatic battery-low detection function. > > > > > > In case of battery-low event, an interrupt generation through > > > the pin INTn (active low) can be enabled, setting the flag BLIE > > > in the register Control_3. > > > > > > This function is activated by the "battery-low-hw-alarm" DT property. > > > > > > Example of use for an NXP i.MX7D board: > > > > > > &i2c3 { > > > clock-frequency = <100000>; > > > pinctrl-names = "default"; > > > pinctrl-0 = <&pinctrl_i2c3>; > > > status = "okay"; > > > > > > pcf2127@51 { > > > compatible = "nxp,pcf2127"; > > > reg = <0x51>; > > > battery-low-hw-alarm; > > > status = "okay"; > > > }; > > > }; > > > > > > > So I'm curious, how do you then use that signal? I have a (not yet sent) > > series adding alarm support for the pcf2127. The issue having BLIE is > > that then this will prevent the alarm to work properly. > > > > So my guess is that you have nINT connected to an LED or something that > > the user can see? > > > > I'm working on our custom embedded board with an NXP i.MX7D, > developed here, in Asem (www.asem.it). > The nINT pin is connected to a GPIO of the MX7 and then > used by an applicative sw, to generate an alarm for the user. > Then, you should probably not enable BLIE because this will cause issues with the alarm functionnality.. It is certainly enough to use RTC_VL_READ periodically. -- Alexandre Belloni, Bootlin Embedded Linux and Kernel engineering https://bootlin.com