From patchwork Fri Dec 9 17:12:37 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Doug Anderson X-Patchwork-Id: 13070033 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 AB2D1C4332F for ; Fri, 9 Dec 2022 17:13:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229939AbiLIRNX (ORCPT ); Fri, 9 Dec 2022 12:13:23 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34810 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229734AbiLIRNV (ORCPT ); Fri, 9 Dec 2022 12:13:21 -0500 Received: from mail-pj1-x1033.google.com (mail-pj1-x1033.google.com [IPv6:2607:f8b0:4864:20::1033]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8B30C4093E for ; Fri, 9 Dec 2022 09:13:14 -0800 (PST) Received: by mail-pj1-x1033.google.com with SMTP id k88-20020a17090a4ce100b00219d0b857bcso5618977pjh.1 for ; Fri, 09 Dec 2022 09:13:14 -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=fGd3e82N31A7l0GFrD4RELU4+SmeP8YESrYNFW7YbDq/1R5jPqb8HNf+yew8ZNCRFM C7/4ccIgu7oVj7ehikAIRQtjKtveYz2hYbWdeapMVOiPP2ZlFmwVaQBpTsw0kUPnRo+M A6RKaIjdiuS+DXbkVcxHNSKfFI/mfyREzSE9s= 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=tSi8ih5hbn9RK6RoaW1gQ5cX9WsOSR3dZKnAtT/sbwm124BfKTjVfTSpiF0nIX9HtJ g/KC/dD7/WNzka6mXJvwucmkFUcmFNmpnzKWFUB4CToAXAtQbtb8c82rs133OOBYy5DG s5gnaqLb22ULtGLRQB+wFzf9TGcspH1OrV7qt2OgIApUtizMDEkDZBRnTWc5HET9jMrB 7HcwhYsfEnqkEC5Xoad7heE1E8mOnx5aUVSrIFRa8oWx5y9HkS7XrUjoD1rV2omAOC82 nHVcKv6/RfFNg39+rxWQ29Qg3tCRverYZwXVoyJeq4UnEhcdpPa7fWr/aM8PxcQNNjSx 6gDQ== X-Gm-Message-State: ANoB5pnEb+sMyF7yLle3EVKB/s08Ci5zc1CS7ZlY6aQRbde6dFUdtNTI sOOhliLqadz1VZsoLtpOQvQ+6g== X-Google-Smtp-Source: AA0mqf5o0cdOIYZpQg4mEqTBzOqbSQQI2YnX0/UwHmDG/Y+0EqLsG00JvO50nunOCSXjjf7bSa5orQ== X-Received: by 2002:a17:902:aa08:b0:189:fb78:a7d4 with SMTP id be8-20020a170902aa0800b00189fb78a7d4mr6267571plb.21.1670605994046; Fri, 09 Dec 2022 09:13:14 -0800 (PST) Received: from tictac2.mtv.corp.google.com ([2620:15c:9d:2:9a82:7898:7bf4:b4f]) by smtp.gmail.com with ESMTPSA id j16-20020a170902da9000b00189c62eac37sm1597503plx.32.2022.12.09.09.13.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 09 Dec 2022 09:13:13 -0800 (PST) From: Douglas Anderson To: Bjorn Andersson Cc: swboyd@chromium.org, Dmitry Torokhov , mka@chromium.org, Yunlong Jia , linux-arm-msm@vger.kernel.org, Konrad Dybcio , linux-input@vger.kernel.org, Douglas Anderson , Andy Gross , Krzysztof Kozlowski , Rob Herring , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v3 1/4] arm64: dts: qcom: sc7180: Bump up trogdor ts_reset_l drive strength Date: Fri, 9 Dec 2022 09:12:37 -0800 Message-Id: <20221209091234.v3.1.I39c387f1e3176fcf340039ec12d54047de9f8526@changeid> X-Mailer: git-send-email 2.39.0.rc1.256.g54fd8350bd-goog In-Reply-To: <20221209171240.1614904-1-dianders@chromium.org> References: <20221209171240.1614904-1-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 Reviewed-by: Konrad Dybcio --- (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 {