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=-5.9 required=3.0 tests=DKIM_ADSP_ALL, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS 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 68869C43441 for ; Tue, 27 Nov 2018 03:57:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 36380208E4 for ; Tue, 27 Nov 2018 03:57:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 36380208E4 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 S1728397AbeK0OyS (ORCPT ); Tue, 27 Nov 2018 09:54:18 -0500 Received: from csm1.csm-office.com.au ([165.228.118.109]:58120 "EHLO sleepy.aussec.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727630AbeK0OyS (ORCPT ); Tue, 27 Nov 2018 09:54:18 -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 wAR3vYVn023150; Tue, 27 Nov 2018 14:57:39 +1100 Received: from csm3.csm-office.com.au (csm3.csm-office.com.au [172.16.0.11]) by aussec.com (Horde Framework) with HTTP; Tue, 27 Nov 2018 14:57:29 +1100 Message-ID: <20181127145729.128452ujmj4uhb55@aussec.com> Date: Tue, 27 Nov 2018 14:57:29 +1100 From: tom burkart To: Rob Herring Cc: "linux-kernel@vger.kernel.org" , devicetree@vger.kernel.org Subject: Re: [PATCH v7 1/4] dt-bindings: pps: descriptor-based gpio, capture-clear addition References: <20181114125432.16044-1-tom@aussec.com> <20181114125432.16044-2-tom@aussec.com> <20181116224919.GA18008@bogus> <20181117213522.12672utznrvpbn56@www.aussec.com> <20181118113502.55634v85ybgkt586@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 Hi Rob, Quoting Rob Herring : > On Sat, Nov 17, 2018 at 6:35 PM tom burkart wrote: >> >> Quoting Rob Herring : >> >> > On Sat, Nov 17, 2018 at 4:35 AM tom burkart wrote: >> >> >> >> Quoting Rob Herring : >> >> >> >> > On Wed, Nov 14, 2018 at 11:54:29PM +1100, Tom Burkart wrote: >> >> >> This patch changes the devicetree bindings for the pps-gpio driver >> >> >> from the integer based ABI to the descriptor based ABI. >> >> > ? That has nothing to do with DT. >> >> >> >> I believe it does, as the change in ABI forces a rename in the DT >> >> naming convention. >> >> This is due to the descriptor based ABI appending "-gpio" or >> "-gpios" (see >> >> Documentation/gpio/base.txt.) >> >> Admittedly, I may have called it by the wrong name due to ignorance, >> >> my apologies. >> > >> > If what you say is correct, then you can't change this driver. You'll >> > break compatibility with any existing DT. >> > >> > Changing the binding reasoning should purely be that this is the >> > preferred form. Bindings must be independent from changing kernel >> > APIs. >> >> See comments from Philip Zabel. I misread the documentation and this >> has now been corrected in v8 of the patch. I hope that eliminates all >> comments made above. >> >> >> >> It also adds >> >> >> documentation for the device tree capture-clear option. The legacy >> >> >> device tree entry for the GPIO pin is supported. >> >> >> >> >> >> Signed-off-by: Tom Burkart >> >> >> --- >> >> >> Documentation/devicetree/bindings/pps/pps-gpio.txt | 8 ++++++-- >> >> >> 1 file changed, 6 insertions(+), 2 deletions(-) >> >> >> >> >> >> diff --git a/Documentation/devicetree/bindings/pps/pps-gpio.txt >> >> >> b/Documentation/devicetree/bindings/pps/pps-gpio.txt >> >> >> index 3683874832ae..6c9fc0998d94 100644 >> >> >> --- a/Documentation/devicetree/bindings/pps/pps-gpio.txt >> >> >> +++ b/Documentation/devicetree/bindings/pps/pps-gpio.txt >> >> >> @@ -5,19 +5,23 @@ a GPIO pin. >> >> >> >> >> >> Required properties: >> >> >> - compatible: should be "pps-gpio" >> >> >> -- gpios: one PPS GPIO in the format described by ../gpio/gpio.txt >> >> >> +- pps-gpios: one PPS GPIO in the format described by ../gpio/gpio.txt >> >> >> +Alternatively (DEPRECATED), instead of pps-gpios above, it may have: >> >> >> +- gpios: one PPS GPIO as above >> >> >> >> >> >> 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 >> >> > >> >> > Is this a h/w thing? or driver configuration? >> >> >> >> Driver configuration. Most of the code was present in the driver, yet >> >> it was not documented, or usable due to a two line (code) omission >> >> (the value was not being fetched from DT). >> > >> > So what determines how you want to configure this? If the user will >> > want to change it, then it should be a sysfs attr and exposed to >> > userspace. If it depends on h/w config for a board then it can be in >> > DT. >> >> Sorry, I misled you somewhat. If the PPS pulse active transition from >> the hardware is on the falling edge, this flag is required to get the >> OS to use that as the active transition. This would not change at the >> user's whim but rather it is dependent on connected hardware. > > This description sounds more like 'assert-falling-edge' than 'capture-clear'. > > I'm still not clear on what 'capture-clear' is. Ignoring my patch for a minute, the pps_gpio_irq_handler will only report a pps PPS_CAPTURECLEAR event if 'capture-clear' is set. As the current pps-gpio driver is not able to set this flag, it cannot ever report a PPS_CAPTURECLEAR event. My patch adds the ability to set this flag and adds the documentation to go with it. Admittedly, I do not require this functionality for what I want, but working with the code, I noticed the omission and decided to add it for someone else to use it, if they need it. I am happy to remove this out of my patch, if you feel this to be the best way forward. Tom