From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.8 required=3.0 tests=DKIM_ADSP_ALL, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8B8C3C6783B for ; Wed, 12 Dec 2018 02:26:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 53B2020839 for ; Wed, 12 Dec 2018 02:26:18 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 53B2020839 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=aussec.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726338AbeLLC0R (ORCPT ); Tue, 11 Dec 2018 21:26:17 -0500 Received: from csm1.csm-office.com.au ([165.228.118.109]:55004 "EHLO sleepy.aussec.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726218AbeLLC0Q (ORCPT ); Tue, 11 Dec 2018 21:26:16 -0500 X-Virus-Scanned: amavisd-new at aussec.com Received: from sneezy.aussec.com (sneezy.aussec.com [172.16.0.4]) by sleepy.aussec.com (8.15.2/8.15.2) with ESMTP id wBC2PuQ4002680; Wed, 12 Dec 2018 13:26:01 +1100 Received: from 1.128.110.99 ([1.128.110.99]) by www.aussec.com (Horde Framework) with HTTP; Wed, 12 Dec 2018 13:25:51 +1100 Message-ID: <20181212132551.48881ybb96b2pay7@www.aussec.com> Date: Wed, 12 Dec 2018 13:25:51 +1100 From: tom burkart To: Rob Herring Cc: "linux-kernel@vger.kernel.org" , devicetree@vger.kernel.org, lukas@fridolin.com Subject: Re: [PATCH v9 3/4] dt-bindings: pps: pps-gpio PPS ECHO implementation References: <20181122094602.5156-1-tom@aussec.com> <20181122094602.5156-2-tom@aussec.com> <20181122094602.5156-3-tom@aussec.com> <20181122094602.5156-4-tom@aussec.com> <20181127150629.10795h1esqtc53ut@aussec.com> <20181211131716.931947v9gya4ajos@www.aussec.com> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; DelSp="Yes"; format="flowed" Content-Disposition: inline Content-Transfer-Encoding: 7bit User-Agent: Internet Messaging Program (IMP) H3 (4.3.9) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Quoting Rob Herring : > On Mon, Dec 10, 2018 at 8:17 PM tom burkart wrote: >> >> Quoting Rob Herring : >> >> > On Mon, Nov 26, 2018 at 10:06 PM tom burkart wrote: >> >> >> >> Quoting Rob Herring : >> >> >> >> > On Thu, Nov 22, 2018 at 3:49 AM Tom Burkart wrote: >> >> >> >> >> >> This patch implements the device tree changes required for the pps >> >> >> echo functionality for pps-gpio, that sysfs claims is available >> >> >> already. >> >> >> >> >> >> This patch was originally written by Lukas Senger as part of a masters >> >> >> thesis project and modified for inclusion into the linux kernel by Tom >> >> >> Burkart. >> >> >> >> >> >> Signed-off-by: Lukas Senger >> >> >> Signed-off-by: Tom Burkart >> >> >> --- >> >> >> Documentation/devicetree/bindings/pps/pps-gpio.txt | 9 +++++++++ >> >> >> 1 file changed, 9 insertions(+) >> >> >> >> >> >> diff --git a/Documentation/devicetree/bindings/pps/pps-gpio.txt >> >> >> b/Documentation/devicetree/bindings/pps/pps-gpio.txt >> >> >> index 1155d49c2699..e09f6f2405c5 100644 >> >> >> --- a/Documentation/devicetree/bindings/pps/pps-gpio.txt >> >> >> +++ b/Documentation/devicetree/bindings/pps/pps-gpio.txt >> >> >> @@ -7,10 +7,15 @@ Required properties: >> >> >> - compatible: should be "pps-gpio" >> >> >> - gpios: one PPS GPIO in the format described by ../gpio/gpio.txt >> >> >> >> >> >> +Additional required properties for the PPS ECHO functionality: >> >> >> +- echo-gpios: one PPS ECHO GPIO in the format described by >> >> ../gpio/gpio.txt >> >> >> +- echo-active-ms: duration in ms of the active portion of >> the echo pulse >> >> >> + >> >> >> Optional properties: >> >> >> - assert-falling-edge: when present, assert is indicated by a >> >> falling edge >> >> >> (instead of by a rising edge) >> >> >> - capture-clear: when present, also capture the PPS clear event >> >> >> +- invert-pps-echo: when present, invert the PPS ECHO pulse >> >> > >> >> > Why do you need this? Can't you just make the echo gpio >> GPIO_ACTIVE_LOW? >> >> > >> >> > BTW, using the flag probably should have been done for >> >> > 'assert-falling-edge' as well. >> >> >> >> The hardware I use expects a positive-going echo pulse, however, it >> >> was really easy to give users the option to have it inverted in case >> >> they use different hardware that expects a negative-going edge. >> > >> > It will be even easier to implement if you use GPIO_ACTIVE_LOW or >> > GPIO_ACTIVE_HIGH as appropriate. If the flag is set appropriately, >> > then gpiod_set_value(gpio, 1) asserts the pulse and >> > gpiod_set_value(gpio, 0) deasserts it no matter which way the h/w is >> > wired. You can then get rid of invert_pps_echo in the driver. >> >> Hi Rob, >> I have looked at the appropriate changes to my code to implement the >> above. However, there is no GPIO_ACTIVE_* as part of the gpiod_flags >> enum (include/linux/gpio/consumer.h). >> >> What am I missing? > > You don't need to know in the driver. You set the gpio state to 1 for > active, 0 for inactive and that does the right thing based on the flag > in the DT. IOW, if the DT defines the GPIO as active low, then setting > the gpio state to 1 will result in the GPIO being 0V. It's a bit > annoying and confusing at first until you realize the driver can just > handle either polarity transparently. Hi Rob, thanks a lot! The penny finally dropped. My patch v12 will have the changes implemented (no invert-pps-echo). Tom