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[2620:137:e000::1:20]) by mx.google.com with ESMTP id nb12-20020a17090b35cc00b00200b014d2adsi16111pjb.26.2022.12.08.11.23.47; Thu, 08 Dec 2022 11:24:01 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@chromium.org header.s=google header.b=Yq20ujLH; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=chromium.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229809AbiLHTVU (ORCPT + 99 others); Thu, 8 Dec 2022 14:21:20 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45818 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229777AbiLHTUx (ORCPT ); Thu, 8 Dec 2022 14:20:53 -0500 Received: from mail-pj1-x102f.google.com (mail-pj1-x102f.google.com [IPv6:2607:f8b0:4864:20::102f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B02509B285 for ; Thu, 8 Dec 2022 11:20:38 -0800 (PST) Received: by mail-pj1-x102f.google.com with SMTP id e7-20020a17090a77c700b00216928a3917so5677247pjs.4 for ; Thu, 08 Dec 2022 11:20:38 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=qBUYq/f5W1QpvWQ1L0owj+9liBAfVOZ5HyYf2BUvGw4=; b=Yq20ujLHdDmxfsm6nXV56O+R5s3byqsOzEHjK+WiS1J/KE/7s2Me27w3dKPKEBUPXj EBxaZvKRup2jGETzG6pHkC4C/xO67Cr3V2UFuWIZ7iYRcD+t8/x/7b6NpJY4r9h9ugBF i2f52c853182eqqlzGcIlS/0+SsTPdNlNu2oo= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=qBUYq/f5W1QpvWQ1L0owj+9liBAfVOZ5HyYf2BUvGw4=; b=I78WiK6/M0LGLVRGDkR8zFF+FbSwj32YoUrhVmdmNiYbwgu5n/etfcu8dAaRnx7q9C 8GBPpizXpzjd1/NDhTof9ut+h4sWyVvlzIFxcEEcAZeTNXSQaWofs+Pw/etUTuBdlxf5 zrGwsIBHg3fuuTR5ClF3O+bDNrUUPW8lFDkD7OgAkQw2JIIXBNgDmR/g2r65jHJT4SkN f4AtIQfwVDZeQJASWOIZzlTeOfXBMT0Mz+M0fVoD6akNHVWdVuFLVVF/iNq6MciGS66W CgDJ3vJw+LMLHqZjRjsgHwqQNeT3+A6m2MZ3KUmLGSWVHX4K1VAXcczheyzT8ghgT3oX VAZw== X-Gm-Message-State: ANoB5pmQfvaBVqQ1y9GoYaWgi+ivK2bnmh+bX+hIXnufwRpG35NjC3LI cwEnectNCQjYMsO79mOjWjsIaw== X-Received: by 2002:a17:903:40cf:b0:189:ccb2:f20a with SMTP id t15-20020a17090340cf00b00189ccb2f20amr3555544pld.49.1670527238392; Thu, 08 Dec 2022 11:20:38 -0800 (PST) Received: from tictac2.mtv.corp.google.com ([2620:15c:9d:2:3aa1:2c62:9ac:4468]) by smtp.gmail.com with ESMTPSA id u5-20020a170902e5c500b00186a2274382sm17112019plf.76.2022.12.08.11.20.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Dec 2022 11:20:37 -0800 (PST) From: Douglas Anderson To: Bjorn Andersson , Dmitry Torokhov Cc: mka@chromium.org, swboyd@chromium.org, linux-arm-msm@vger.kernel.org, linux-input@vger.kernel.org, Yunlong Jia , Konrad Dybcio , Douglas Anderson , Johnny Chuang , linux-kernel@vger.kernel.org Subject: [PATCH 5/5] Input: elants_i2c: Delay longer with reset asserted Date: Thu, 8 Dec 2022 11:20:06 -0800 Message-Id: <20221208111910.5.I6edfb3f459662c041563a54e5b7df727c27caaba@changeid> X-Mailer: git-send-email 2.39.0.rc1.256.g54fd8350bd-goog In-Reply-To: <20221208192006.1070898-1-dianders@chromium.org> References: <20221208192006.1070898-1-dianders@chromium.org> MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1751674982030311079?= X-GMAIL-MSGID: =?utf-8?q?1751674982030311079?= The elan touchscreen datasheet says that the reset GPIO only needs to be asserted for 500us in order to reset the regulator. The problem is that some boards need a level shifter between the signals on the GPIO controller and the signals on the touchscreen. All of these extra components on the line can slow the transition of the signals. On one board, we measured the reset line and saw that it took almost 1.8ms to go low. Even after we bumped up the "drive strength" of the signal from the default 2mA to 8mA we still saw it take 421us for the signal to go low. In order to account for this we let's lengthen the amount of time that we keep the reset asserted. Let's bump it up from 500us to 5000us. That's still a relatively short amount of time and is much safer. It should be noted that this fixes real problems. Case in point: 1. The touchscreen power rail may be shared with another device (like an eDP panel). That means that at probe time power might already be on. 2. In probe we grab the reset GPIO and assert it (make it low). 3. We turn on power (a noop since it was already on). 4. We wait 500us. 5. We deassert the reset GPIO. With the above case and only a 500us delay we saw only a partial reset asserted, which is bad. Giving it 5ms is overkill but feels safer in case someone else has a different level shifter setup. Signed-off-by: Douglas Anderson Reviewed-by: Matthias Kaehlcke --- drivers/input/touchscreen/elants_i2c.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/input/touchscreen/elants_i2c.c b/drivers/input/touchscreen/elants_i2c.c index 879a4d984c90..377adf89b25c 100644 --- a/drivers/input/touchscreen/elants_i2c.c +++ b/drivers/input/touchscreen/elants_i2c.c @@ -114,7 +114,7 @@ /* calibration timeout definition */ #define ELAN_CALI_TIMEOUT_MSEC 12000 -#define ELAN_POWERON_DELAY_USEC 500 +#define ELAN_POWERON_DELAY_USEC 5000 #define ELAN_RESET_DELAY_MSEC 20 /* FW boot code version */