From patchwork Thu Dec 8 19:20:02 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Doug Anderson X-Patchwork-Id: 13068692 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 DD1A1C4167B for ; Thu, 8 Dec 2022 19:20:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229691AbiLHTUi (ORCPT ); Thu, 8 Dec 2022 14:20:38 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45308 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229612AbiLHTUg (ORCPT ); Thu, 8 Dec 2022 14:20:36 -0500 Received: from mail-pj1-x102b.google.com (mail-pj1-x102b.google.com [IPv6:2607:f8b0:4864:20::102b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6BF908F0B3 for ; Thu, 8 Dec 2022 11:20:32 -0800 (PST) Received: by mail-pj1-x102b.google.com with SMTP id gt4so844836pjb.1 for ; Thu, 08 Dec 2022 11:20:32 -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=mU15PmQ7y4jCLhzpRiDgBwZPVlqL2rxQ5MC828vQiLw=; b=UtZBnVwuE1PrB9zKCulUevgNmkD3pmq5tiL+Ard+l0p/FsDDyKgRZOr6mI5GO/cwi0 G75JjAG+E2Zf5gO0nim5H8WlklfKjtuSB7iRUKUIXLz6Soe4y5w1JK98KRj2z3F/rGRi cdz6Gvr6WqpUlCm8Clr2G2YPnYKsm5asVhARM= 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=mU15PmQ7y4jCLhzpRiDgBwZPVlqL2rxQ5MC828vQiLw=; b=q68ATJRsZccu0f4rC3KBXaRxqKZoO7Gs1QyvgMEn8Ixpx8mA39e9zyw06paF1qBTh7 5wWwCinC9h/gWN46gKBJTk74FwIOM6T/ALw0ORHtBvaIKAPDapvHfYvc8WVbpj1ZbhLL fG8yrKEZHU7/rGTX4Zi0rcbzkotKumyfyxPnaFUOwM40Q9Sk8MnMnF1Tk8sFNbavqWGk ucN7c0LEp5x0n7Sx/DzvCJ7m79ra4j41ju6dC5z7BHe5I4z5xJrRwlhnNyPMs9oBvqyo M3WEdpBT3MN+W/2jhi6KNf0NerqJH7MQNCNhdkx/pw+QPqLkyjs8FxpojO70a68zb/5+ fzJg== X-Gm-Message-State: ANoB5pmv5xdPPpu2FY56M681M6bTU50uykqm6q0lcRZZVsPXbXSFYI9i UydenbNtGr113nZc0gHCYVQI8XgigtE1VQsp X-Google-Smtp-Source: AA0mqf4yVAiZHjwlp/KwHCa/AKRbwhwwJPJpOKG+mWu/pk9FEGcH6atyJYZwqS+NbHGnEnd3Q0MT6Q== X-Received: by 2002:a17:902:6b05:b0:185:441f:7087 with SMTP id o5-20020a1709026b0500b00185441f7087mr2916552plk.12.1670527231917; Thu, 08 Dec 2022 11:20:31 -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.76.2022.12.08.11.20.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Dec 2022 11:20:31 -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 , Andy Gross , Krzysztof Kozlowski , Rob Herring , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 1/5] arm64: dts: qcom: sc7180: Bump up trogdor ts_reset_l drive strength Date: Thu, 8 Dec 2022 11:20:02 -0800 Message-Id: <20221208111910.1.I39c387f1e3176fcf340039ec12d54047de9f8526@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 Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@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 --- 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 {