From patchwork Fri Dec 9 02:06:08 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Doug Anderson X-Patchwork-Id: 13069165 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9655EC4332F for ; Fri, 9 Dec 2022 02:06:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229888AbiLICGb (ORCPT ); Thu, 8 Dec 2022 21:06:31 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36442 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230100AbiLICG3 (ORCPT ); Thu, 8 Dec 2022 21:06:29 -0500 Received: from mail-pl1-x633.google.com (mail-pl1-x633.google.com [IPv6:2607:f8b0:4864:20::633]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6CBA87D07E for ; Thu, 8 Dec 2022 18:06:28 -0800 (PST) Received: by mail-pl1-x633.google.com with SMTP id s7so3391968plk.5 for ; Thu, 08 Dec 2022 18:06:28 -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=M88P4SMh5VCPJCyuLc/w2B8fWJUsM71IvdRT7VAjmHQ=; b=XIV9gS7alHxSUtR0tKaSg1ZlTvjuvanMhkxu9gP+QpjiM2dNoCFBdqxhXqHxm0gQxK fiG35WMYsI4gJmDpVdNgZQIe+pWpRzesNMP0PihtGP8T7c2YYBxNcXh1lAAHS87CMrD3 naYNadu9ysQ3fHsQ1mFE0avh4w5DRqRtW5ZYY= 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=M88P4SMh5VCPJCyuLc/w2B8fWJUsM71IvdRT7VAjmHQ=; b=Zzixf/oqXSLUAG/rX6xr8Bwbv+5L++UPMN4z5b2SVE+DuAMYuXQ/2+RiUa8GGGzvJV sUZQ4zYdfhZ86Jzc6ok0igPyWKBFXLk4aKPECdqgohYJrHG6JM+R0r8ADU2PiCdmBNkJ 6B6ch1J14lVr0gC5uvJ9EVPNjBQ87XYQTYoj/rNLk3MLXb/Y88DKEwW7oFRnULWtdvyC spZ48zj0MG9UAF8PVHoRNNP8W0PdicL9R5H7b86eBuXq6en2pNZNmu2rH0W3lN4q0TsT uFqFrR+MF7pZ4MPkrIp3cdE6zQCZbzaJ4CiWFh1HfbcLMcKfw9msaYp/FKrJY3SY0QvS VZ6g== X-Gm-Message-State: ANoB5pnYCRO+1FXVyWhD0Bk1xiOkL+sM08WT/gHwOmySY3USKm700Kdl eIk83Si7+9ju51xn5ir7UxeVUA== X-Google-Smtp-Source: AA0mqf7krx9sgecPRwfwbatLdx7a2LUAZpwNfCjIW4cK+SLxXzqoatENDBySUKpqsRQPnNfvmPf3cQ== X-Received: by 2002:a17:90a:f614:b0:218:87cf:1bed with SMTP id bw20-20020a17090af61400b0021887cf1bedmr4772786pjb.2.1670551587920; Thu, 08 Dec 2022 18:06:27 -0800 (PST) Received: from tictac2.mtv.corp.google.com ([2620:15c:9d:2:9a82:7898:7bf4:b4f]) by smtp.gmail.com with ESMTPSA id h3-20020a17090a648300b00218ddc8048bsm233473pjj.34.2022.12.08.18.06.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Dec 2022 18:06:27 -0800 (PST) From: Douglas Anderson To: Bjorn Andersson , Dmitry Torokhov Cc: linux-arm-msm@vger.kernel.org, mka@chromium.org, Yunlong Jia , Konrad Dybcio , linux-input@vger.kernel.org, swboyd@chromium.org, Douglas Anderson , Andy Gross , Krzysztof Kozlowski , Rob Herring , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 1/5] arm64: dts: qcom: sc7180: Bump up trogdor ts_reset_l drive strength Date: Thu, 8 Dec 2022 18:06:08 -0800 Message-Id: <20221208180603.v2.1.I39c387f1e3176fcf340039ec12d54047de9f8526@changeid> X-Mailer: git-send-email 2.39.0.rc1.256.g54fd8350bd-goog In-Reply-To: <20221209020612.1303267-1-dianders@chromium.org> References: <20221209020612.1303267-1-dianders@chromium.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-input@vger.kernel.org On at least one board (pazquel360) the reset line for the touchscreen was scoped and found to take almost 2 ms to fall when we drove it low. This wasn't great because the Linux driver for the touchscreen (the elants_i2c driver) thinks it can do a 500 us reset pulse. If we bump the drive strength to 8 mA then the reset line went down in ~421 us. NOTE: we could apply this fix just for pazquel360, but: * Probably other trogdor devices have similar timings and it's just that nobody has noticed it before. * There are other trogdor boards using the same elan driver that tries to do 500 us reset pulses. * Bumping the drive strength to 8mA across the board won't hurt. This isn't a high speed signal or anything. Signed-off-by: Douglas Anderson Reviewed-by: Matthias Kaehlcke --- (no changes since v1) arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi b/arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi index f1defb94d670..ff1c7aa6a722 100644 --- a/arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi +++ b/arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi @@ -1376,7 +1376,15 @@ ts_reset_l: ts-reset-l-state { pins = "gpio8"; function = "gpio"; bias-disable; - drive-strength = <2>; + + /* + * The reset GPIO to the touchscreen takes almost 2ms to drop + * at the default drive strength. When we bump it up to 8mA it + * falls in under 500us. We want this to be fast since the Elan + * datasheet (and any drivers written based on it) talk about using + * a 500 us reset pulse. + */ + drive-strength = <8>; }; sdc1_on: sdc1-on-state {