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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 18F35C3A59E for ; Mon, 2 Sep 2019 14:22:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EEBDC21744 for ; Mon, 2 Sep 2019 14:22:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731492AbfIBOW6 (ORCPT ); Mon, 2 Sep 2019 10:22:58 -0400 Received: from relay3-d.mail.gandi.net ([217.70.183.195]:49011 "EHLO relay3-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726436AbfIBOW6 (ORCPT ); Mon, 2 Sep 2019 10:22:58 -0400 X-Originating-IP: 86.207.98.53 Received: from localhost (aclermont-ferrand-651-1-259-53.w86-207.abo.wanadoo.fr [86.207.98.53]) (Authenticated sender: alexandre.belloni@bootlin.com) by relay3-d.mail.gandi.net (Postfix) with ESMTPSA id 92B5A6000A; Mon, 2 Sep 2019 14:22:54 +0000 (UTC) Date: Mon, 2 Sep 2019 16:22:51 +0200 From: Alexandre Belloni To: Eugen.Hristev@microchip.com Cc: peda@axentia.se, wsa@the-dreams.de, mark.rutland@arm.com, Ludovic.Desroches@microchip.com, linux-i2c@vger.kernel.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, pierre-yves.mordret@st.com, robh+dt@kernel.org Subject: Re: [PATCH v4 2/9] dt-bindings: i2c: add bindings for i2c analog and digital filter Message-ID: <20190902142251.GC21922@piout.net> References: <1567418773-2427-1-git-send-email-eugen.hristev@microchip.com> <1567418773-2427-3-git-send-email-eugen.hristev@microchip.com> <9a9c209c-2fb8-0a4c-4e0a-b04fefda3360@axentia.se> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Eugen, On 02/09/2019 14:15:14+0000, Eugen.Hristev@microchip.com wrote: > On 02.09.2019 13:49, Peter Rosin wrote: > > > On 2019-09-02 12:12, Eugen.Hristev@microchip.com wrote: > >> From: Eugen Hristev > >> > >> Some i2c controllers have a built-in digital or analog filter. > >> This is specifically required depending on the hardware PCB/board. > >> Some controllers also allow specifying the maximum width of the > >> spikes that can be filtered. The width length can be specified in nanoseconds. > >> > >> Signed-off-by: Eugen Hristev > >> --- > >> Documentation/devicetree/bindings/i2c/i2c.txt | 11 +++++++++++ > >> 1 file changed, 11 insertions(+) > >> > >> diff --git a/Documentation/devicetree/bindings/i2c/i2c.txt b/Documentation/devicetree/bindings/i2c/i2c.txt > >> index 44efafd..8dbff67 100644 > >> --- a/Documentation/devicetree/bindings/i2c/i2c.txt > >> +++ b/Documentation/devicetree/bindings/i2c/i2c.txt > >> @@ -55,6 +55,17 @@ wants to support one of the below features, it should adapt the bindings below. > >> Number of nanoseconds the SDA signal takes to fall; t(f) in the I2C > >> specification. > >> > >> +- i2c-analog-filter > >> + Enable analog filter for i2c lines. > >> + > >> +- i2c-digital-filter > >> + Enable digital filter for i2c lines. > >> + > >> +- i2c-filter-width-ns > >> + Width of spikes which can be filtered by either digital or analog > >> + filters (i2c-analog-filtr or i2c-digital-filtr). This width is specified > > > > filtr -> filter (two instances) > > > > What if you want/need to have different bandwidth for the digital and analog > > filters? After all, this is a generic binding... > > For our needs, this is enough: the purpose of the filters is to avoid > noise on the lines, the noise is as big as it is for the digital and for > the analog filters, since we use an absolute measurement for them. So I > do not know how useful it would be to make a difference. > You are adding generic properties so they have to be generic and not tied to your particular use case. -- Alexandre Belloni, Bootlin Embedded Linux and Kernel engineering https://bootlin.com