Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751441AbdIJKoC (ORCPT ); Sun, 10 Sep 2017 06:44:02 -0400 Received: from smtpcmd10101.aruba.it ([62.149.156.101]:42248 "EHLO smtpcmd10101.aruba.it" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751405AbdIJKoA (ORCPT ); Sun, 10 Sep 2017 06:44:00 -0400 Subject: Re: [PATCH] pps-gpio: use IRQ edge config when not capturing both edges To: Tim Harvey , "discussions@linuxpps.org" Cc: linux-kernel@vger.kernel.org, Koen Vandeputte References: <1504900414-1514-1-git-send-email-tharvey@gateworks.com> From: Rodolfo Giometti Message-ID: Date: Sun, 10 Sep 2017 12:43:58 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <1504900414-1514-1-git-send-email-tharvey@gateworks.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1575 Lines: 42 On 08/09/2017 21:53, Tim Harvey wrote: > PPS signals with very short pulse-widths can be missed if their state > changes by the time the interrupt handler reads the GPIO pin state. > > To avoid this in the case where we are only looking for one edge we can > use the edge configuration for the pin state but fall back to reading the > pin if both edges are being watched. I disagree. The "rising_edge" status should be get from the hardware and not derived by an empirical computation. Or, at least, it should be specifically activated by setting something like this: pps { pinctrl-names = "default"; pinctrl-0 = <&pinctrl_pps>; gpios = <&gpio1 26 GPIO_ACTIVE_HIGH>; Yes-I-want-get-signal-status-in-an-epirical-way; compatible = "pps-gpio"; status = "okay"; }; This setting should also print a warning in order to be clear for the user that he/she should know what he/she is doing. Then the code should check also the compatibility with property "assert-falling-edge"... Ciao, Rodolfo -- HCE Engineering e-mail: giometti@hce-engineering.it GNU/Linux Solutions giometti@enneenne.com Linux Device Driver giometti@linux.it Embedded Systems phone: +39 349 2432127 UNIX programming skype: rodolfo.giometti Cosino Project - the quick prototyping embedded system - www.cosino.it Freelance ICT Italia - Consulente ICT Italia - www.consulenti-ict.it