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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 35052C433DB for ; Mon, 29 Mar 2021 13:07:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 01CA761929 for ; Mon, 29 Mar 2021 13:07:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231600AbhC2NHB (ORCPT ); Mon, 29 Mar 2021 09:07:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55626 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231465AbhC2NG2 (ORCPT ); Mon, 29 Mar 2021 09:06:28 -0400 Received: from metis.ext.pengutronix.de (metis.ext.pengutronix.de [IPv6:2001:67c:670:201:290:27ff:fe1d:cc33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2BD75C061756 for ; Mon, 29 Mar 2021 06:06:28 -0700 (PDT) Received: from pty.hi.pengutronix.de ([2001:67c:670:100:1d::c5]) by metis.ext.pengutronix.de with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1lQrb3-0006o4-6z; Mon, 29 Mar 2021 15:06:21 +0200 Received: from ore by pty.hi.pengutronix.de with local (Exim 4.89) (envelope-from ) id 1lQrb2-000345-I5; Mon, 29 Mar 2021 15:06:20 +0200 Date: Mon, 29 Mar 2021 15:06:20 +0200 From: Oleksij Rempel To: Jonathan Cameron Cc: Rob Herring , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Pengutronix Kernel Team , David Jander , Robin van der Gracht , linux-iio@vger.kernel.org, Lars-Peter Clausen , Peter Meerwald-Stadler , Dmitry Torokhov Subject: Re: [PATCH v5 1/3] dt-bindings:iio:adc: add generic settling-time-us and oversampling-ratio channel properties Message-ID: <20210329130620.utfdlgwzixrenqka@pengutronix.de> References: <20210329073131.1759-1-o.rempel@pengutronix.de> <20210329073131.1759-2-o.rempel@pengutronix.de> <20210329112532.174825d6@jic23-huawei> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20210329112532.174825d6@jic23-huawei> X-Sent-From: Pengutronix Hildesheim X-URL: http://www.pengutronix.de/ X-IRC: #ptxdist @freenode X-Accept-Language: de,en X-Accept-Content-Type: text/plain X-Uptime: 14:57:12 up 117 days, 3:03, 48 users, load average: 0.14, 0.14, 0.09 User-Agent: NeoMutt/20170113 (1.7.2) X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::c5 X-SA-Exim-Mail-From: ore@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 29, 2021 at 11:25:32AM +0100, Jonathan Cameron wrote: > On Mon, 29 Mar 2021 09:31:29 +0200 > Oleksij Rempel wrote: > > > Settling time and over sampling is a typical challenge for different IIO ADC > > devices. So, introduce channel specific settling-time-us and oversampling-ratio > > properties to cover this use case. > > > > Signed-off-by: Oleksij Rempel > > --- > > Documentation/devicetree/bindings/iio/adc/adc.yaml | 8 ++++++++ > > 1 file changed, 8 insertions(+) > > > > diff --git a/Documentation/devicetree/bindings/iio/adc/adc.yaml b/Documentation/devicetree/bindings/iio/adc/adc.yaml > > index 912a7635edc4..d5bc86d2a2af 100644 > > --- a/Documentation/devicetree/bindings/iio/adc/adc.yaml > > +++ b/Documentation/devicetree/bindings/iio/adc/adc.yaml > > @@ -39,4 +39,12 @@ properties: > > The first value specifies the positive input pin, the second > > specifies the negative input pin. > > > > + settling-time-us: > > + description: > > + Time between enabling the channel and firs stable readings. > > first ack > > + > > + oversampling-ratio: > > + $ref: /schemas/types.yaml#/definitions/uint32 > > + description: Number of data samples which are averaged for each read. > > I think I've asked about this in previous reviews, but I want a clear statement > of why you think this property is a feature of the 'board' (and hence should be > in device tree) rather than setting sensible defaults and leaving any control > to userspace? yes, my reply was: > Oversampling is used as replacement of or addition to the low-pass filter. The > filter can be implemented on board, but it will change settling time > characteristic. Since low-pass filter is board specific characteristic, this > property belongs in device tree as well. I could imagine that this values can be overwritten from user space for diagnostic, but we need some working default values. Should I integrate this comment in to the yaml? Regards, Oleksij -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |