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=-3.6 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 712C5C43461 for ; Mon, 14 Sep 2020 22:32:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2E5CF21974 for ; Mon, 14 Sep 2020 22:32:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="ULWIxTGH" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726019AbgINWcp (ORCPT ); Mon, 14 Sep 2020 18:32:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56426 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725953AbgINWco (ORCPT ); Mon, 14 Sep 2020 18:32:44 -0400 Received: from mail-pl1-x643.google.com (mail-pl1-x643.google.com [IPv6:2607:f8b0:4864:20::643]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9725DC06174A; Mon, 14 Sep 2020 15:32:42 -0700 (PDT) Received: by mail-pl1-x643.google.com with SMTP id c3so255750plz.5; Mon, 14 Sep 2020 15:32:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to; bh=r//p/musXc3E44T/FgdUApsZyFMshBSitW0+8TNcXbk=; b=ULWIxTGHbmtZ6Bfv4rRYq7a8z/MxMxLopZWyf7rl7tN5BryGlRaDz6lJJzX5Oti+t5 eMTYHhRLPffavbQ5kQ4jtqLLlSl+4dcoJWcOlRFEZ4xpDN5Kta+Oaz+RrRpAG2tVO4R+ 4ke80npHkpQ8Uywqp21MH7gckwzTbgJNPxphQYXm1vuBPZW8fL5MXfrTyBe4oCKBMkJb gKty8foAj3oecz24WXabb8VW78QPwzYkyBU7mpH1q1RB1c0zfhfqN1l+aDFXSnA7va2f g7axvzA1jlehfGe7OxsKfXbcOM5fkHc7z9cX/56y5IWYG7stt6xdQLR1oHqf0s8dS31n IMeQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to; bh=r//p/musXc3E44T/FgdUApsZyFMshBSitW0+8TNcXbk=; b=J+pRJ42rxAMCpjZ/bQuRFlvlpB9ZcE0ZTZ1x1mQt2JKg9RrmQpT/Hm+2GYqA35e87I EyodvLGdnTAuxw7pVwJ3TsU/DYydPLowjfp0sVFdMGXnWncEcjzg7w9nSa/nBI2SqSTw DSE18lUhW25gr1iJGCFLzxqjO1WvDTL8Jl9ilkDQeiQ5UWfosgF8CsfmQEKW81p4EiBA YBp+pVbBXBJza+uSHHe77iveIVl0vjRkWHazgmZnJHcDdyDpnshepLSXejFv/Mbzs01y XYBzx7p/hHV64QUoFAvYZgJ3/2ZlutyJgXbvTEJCIGKQTmYlEFbui8Cr8JMh05ytoshW n2Bg== X-Gm-Message-State: AOAM530XChoNLw6fPsStcBk5SYBYQDI9vOeaVq+mv+Y7idFMc8o88N8i zohsWV1z6KvX3lBHg9Ng9mU= X-Google-Smtp-Source: ABdhPJyEnF3LW6RMiq4POQ83WkohABQfg9k25KGzXwnO7DRBjpCyFlxTf9NdpTcztxitpFRf/0NlnA== X-Received: by 2002:a17:90a:9d82:: with SMTP id k2mr1354470pjp.197.1600122761412; Mon, 14 Sep 2020 15:32:41 -0700 (PDT) Received: from dtor-ws ([2620:15c:202:201:a6ae:11ff:fe11:fcc3]) by smtp.gmail.com with ESMTPSA id s24sm9276012pgv.55.2020.09.14.15.32.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Sep 2020 15:32:40 -0700 (PDT) Date: Mon, 14 Sep 2020 15:32:38 -0700 From: Dmitry Torokhov To: Dmitry Osipenko , Rob Herring Cc: Jiada Wang , nick@shmanahar.org, linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, andy.shevchenko@gmail.com, erosca@de.adit-jv.com, Andrew_Gabbasov@mentor.com Subject: Re: [PATCH v4 1/1] Input: atmel_mxt_ts - implement I2C retries Message-ID: <20200914223238.GD1681290@dtor-ws> References: <20200912005521.26319-1-jiada_wang@mentor.com> <20200913165644.GF1665100@dtor-ws> <65d1b9f2-a8e3-6398-712d-41d8067d06a1@gmail.com> <20200914193340.GV1665100@dtor-ws> <20200914193603.GW1665100@dtor-ws> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Sender: linux-input-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-input@vger.kernel.org On Tue, Sep 15, 2020 at 12:33:18AM +0300, Dmitry Osipenko wrote: > 14.09.2020 22:36, Dmitry Torokhov пишет: > > On Mon, Sep 14, 2020 at 12:33:40PM -0700, Dmitry Torokhov wrote: > >> On Mon, Sep 14, 2020 at 08:29:44PM +0300, Dmitry Osipenko wrote: > >>> 13.09.2020 19:56, Dmitry Torokhov пишет: > >>>> Hi Jiada, > >>>> > >>>> On Sat, Sep 12, 2020 at 09:55:21AM +0900, Jiada Wang wrote: > >>>>> From: Nick Dyer > >>>>> > >>>>> Some maXTouch chips (eg mXT1386) will not respond on the first I2C request > >>>>> when they are in a sleep state. It must be retried after a delay for the > >>>>> chip to wake up. > >>>> > >>>> Do we know when the chip is in sleep state? Can we do a quick I2C > >>>> transaction in this case instead of adding retry logic to everything? Or > >>>> there is another benefit for having such retry logic? > >>> > >>> Hello! > >>> > >>> Please take a look at page 29 of: > >>> > >>> https://ww1.microchip.com/downloads/en/DeviceDoc/mXT1386_1vx_Datasheet_LX.pdf > >>> > >>> It says that the retry is needed after waking up from a deep-sleep mode. > >>> > >>> There are at least two examples when it's needed: > >>> > >>> 1. Driver probe. Controller could be in a deep-sleep mode at the probe > >>> time, and then first __mxt_read_reg() returns I2C NACK on reading out TS > >>> hardware info. > >>> > >>> 2. Touchscreen input device is opened. The touchscreen is in a > >>> deep-sleep mode at the time when input device is opened, hence first > >>> __mxt_write_reg() invoked from mxt_start() returns I2C NACK. > >>> > >>> I think placing the retries within __mxt_read() / write_reg() should be > >>> the most universal option. > >>> > >>> Perhaps it should be possible to add mxt_wake() that will read out some > >>> generic register > >> > >> I do not think we need to read a particular register, just doing a quick > >> read: > >> > >> i2c_smbus_xfer(client->adapter, client->addr, > >> 0, I2C_SMBUS_READ, 0, I2C_SMBUS_BYTE, &dummy) > >> > >> should suffice. > >> > >>> and then this helper should be invoked after HW > >>> resetting (before mxt_read_info_block()) and from mxt_start() (before > >>> mxt_set_t7_power_cfg()). But this approach feels a bit fragile to me. > >>> > >> > >> Actually, reading the spec, it all depends on how the WAKE pin is wired > >> up on a given board. In certain setups retrying transaction is the right > >> approach, while in others explicit control is needed. So indeed, we need > >> a "wake" helper that we should call in probe and resume paths. > > The WAKE-GPIO was never supported and I'm not sure whether anyone > actually needs it. I think we could ignore this case until anyone would > really need and could test it. Right, I am not advocating adding GPIO control right away, I was simply arguing why I believe we should separate wakeup handling from normal communication handling. > > > By the way, I would like to avoid the unnecessary retries in probe paths > > if possible. I.e. on Chrome OS we really keep an eye on boot times and > > in case of multi-sourced touchscreens we may legitimately not have > > device at given address. > > We could add a new MXT1386 DT compatible and then do: > > static void mxt_wake(struct mxt_data *data) > { > struct i2c_client *client = data->client; > struct device *dev = &data->client->dev; > union i2c_smbus_data dummy; > > if (!of_device_is_compatible(dev, "atmel,mXT1386")) > return; > > /* TODO: add WAKE-GPIO support */ > > i2c_smbus_xfer(client->adapter, client->addr, > 0, I2C_SMBUS_READ, 0, I2C_SMBUS_BYTE, > &dummy); > > msleep(MXT_WAKEUP_TIME); > } > > Jiada, will you be able to re-work this patch? Please note that the new > "atmel,mXT1386" DT compatible needs to be added into the > atmel,maxtouch.txt binding. Another option is to have a device property "atmel,wakeup-type" or something, in case there are more Atmel variants needing this. Rob, any preferences here? Thanks. -- Dmitry