From nobody Sat Sep 21 04:41:23 2024 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 AD9E2C61DA3 for ; Tue, 21 Feb 2023 18:10:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232006AbjBUSJk (ORCPT ); Tue, 21 Feb 2023 13:09:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60386 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230262AbjBUSI4 (ORCPT ); Tue, 21 Feb 2023 13:08:56 -0500 Received: from mail-wm1-x32e.google.com (mail-wm1-x32e.google.com [IPv6:2a00:1450:4864:20::32e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EF9FA2E0C3 for ; Tue, 21 Feb 2023 10:08:07 -0800 (PST) Received: by mail-wm1-x32e.google.com with SMTP id l7-20020a05600c1d0700b003dc4050c94aso3719477wms.4 for ; Tue, 21 Feb 2023 10:08:07 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.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=pyXE7dTHWFCFp1MXqwgdHIOsHgvb6Bb+CE7d2W8RwzE=; b=VnoikhGoavCAJuf2ydSEiBwyVw9h/xyylr0SIVyNnZO5gDGPX2QC4hWwzud5yCwDKU UrYNKjlpGaPx8a8A6yQp5uf+s+1v77lRFz1e1QJ2sl2iJIv386XMi13WpWDuSBEaJUf8 Y4kWrGIybrzff4xV7XTfYHeQTEeBPaQv8tNKUise0uog0OXD/FrzLj9olNr1bTRsuE/v 9BGCcklp5Z8fspWR1OZu7V2/UG15GSRQQkK+t8VdcWxg8W05ZIHhNiyZ6u7gGlAiUHRr cypNwmJrLnQdXv70AZOaRLJR0tkG2FGWgiqnDrwdQS1ak5XluLbiqqV4vnvMInUvgxxt 6jug== 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=pyXE7dTHWFCFp1MXqwgdHIOsHgvb6Bb+CE7d2W8RwzE=; b=J+Ziao9yzkBI6pHVUHpFaak2bH59sH6pWqioUCjMfb6QTayeXUEHUwWp0GWrxA7WmD uY94I2C7ZE7YkUQE8pLktYghcmz02wNf1QM6qqkUaSUkzMwB2R6CCO4vQeCosFV4ebjK brMCU7QFD1o6OIEGlPZIYBx+VvRshOMs54sjdI7POYihpdUefm5miDQF3Ru7p/khzh6m e3/nEwzlG6Y6C68pXvRzvvvTmqaUebYWlOUkjMuF1z1FqkaHSyqecXNZBLDPSzTloE9K XzCImNffprmEAzHMg/TwfkGftJ/xQNImE/FGakWymeqDwvLkNpV/s3dMum6keeKyza7/ cIug== X-Gm-Message-State: AO0yUKX98VuiI5esuHgBY3CClYn3gMeOco6ecsSdSuiJ5+TEsYsnAd6D UuhdvGkQm7F93OwyuY1I13Cnpg== X-Google-Smtp-Source: AK7set8F4G22Oy+oAsm0sMRDvyftq/VUaX4DNaWPoaDFSj2XbAYcpOfOcR3l4xQNpw/lcjEAGYwOtQ== X-Received: by 2002:a05:600c:3196:b0:3df:e468:17dc with SMTP id s22-20020a05600c319600b003dfe46817dcmr3998250wmp.40.1677002887449; Tue, 21 Feb 2023 10:08:07 -0800 (PST) Received: from mai.box.freepro.com ([2a05:6e02:1041:c10:1e9:315c:bb40:e382]) by smtp.gmail.com with ESMTPSA id c128-20020a1c3586000000b003e21558ee9dsm5107815wma.2.2023.02.21.10.08.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Feb 2023 10:08:07 -0800 (PST) From: Daniel Lezcano To: rafael@kernel.org, daniel.lezcano@linaro.org Cc: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, Amit Kucheria , Zhang Rui , Thierry Reding , Jonathan Hunter , =?UTF-8?q?Niklas=20S=C3=B6derlund?= , Baolin Wang , Gregory Greenman , Kunihiko Hayashi , linux-tegra@vger.kernel.org (open list:TEGRA ARCHITECTURE SUPPORT) Subject: [PATCH v2 12/16] thermal/drivers/tegra: Remove unneeded lock when setting a trip point Date: Tue, 21 Feb 2023 19:07:06 +0100 Message-Id: <20230221180710.2781027-13-daniel.lezcano@linaro.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230221180710.2781027-1-daniel.lezcano@linaro.org> References: <20230221180710.2781027-1-daniel.lezcano@linaro.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" The function tegra_tsensor_enable_hw_channel() takes the thermal zone lock to prevent "a potential" race with a call to set_trips() callback. The driver must not play with the thermal framework core code internals. The tegra_tsensor_enable_hw_channel() is called by: - the suspend / resume callbacks - the probe function after the thermal zones are registered The thermal zone lock taken in this function is supposed to protect from a call to the set_trips() callback which writes in the same register. The potential race is when suspend / resume are called at the same time as set_trips. This one is called only in thermal_zone_device_update(). - At suspend time, the 'in_suspend' is set, thus the thermal_zone_device_update() bails out immediately and set_trips is not called during this moment. - At resume time, the thermal zone is updated at PM_POST_SUSPEND, thus the driver has already set the TH2 temperature. - At probe time, we register the thermal zone and then we set the TH2. The only scenario I can see so far is the interrupt fires, the thermal_zone_update() is called exactly at the moment tegra_tsensor_enable_hw_channel() a few lines after registering it. Disable the interrupt before setting up the hw channels and then enable it. We close the potential race window without using the thermal zone's lock. Signed-off-by: Daniel Lezcano --- drivers/thermal/tegra/tegra30-tsensor.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff --git a/drivers/thermal/tegra/tegra30-tsensor.c b/drivers/thermal/tegr= a/tegra30-tsensor.c index 4b2ea17910cd..3506c3f3c474 100644 --- a/drivers/thermal/tegra/tegra30-tsensor.c +++ b/drivers/thermal/tegra/tegra30-tsensor.c @@ -359,9 +359,6 @@ static int tegra_tsensor_enable_hw_channel(const struct= tegra_tsensor *ts, =20 tegra_tsensor_get_hw_channel_trips(tzd, &hot_trip, &crit_trip); =20 - /* prevent potential racing with tegra_tsensor_set_trips() */ - mutex_lock(&tzd->lock); - dev_info_once(ts->dev, "ch%u: PMC emergency shutdown trip set to %dC\n", id, DIV_ROUND_CLOSEST(crit_trip, 1000)); =20 @@ -404,8 +401,6 @@ static int tegra_tsensor_enable_hw_channel(const struct= tegra_tsensor *ts, val |=3D FIELD_PREP(TSENSOR_SENSOR0_CONFIG0_INTR_THERMAL_RST_EN, 1); writel_relaxed(val, tsc->regs + TSENSOR_SENSOR0_CONFIG0); =20 - mutex_unlock(&tzd->lock); - err =3D thermal_zone_device_enable(tzd); if (err) { dev_err(ts->dev, "ch%u: failed to enable zone: %d\n", id, err); @@ -592,12 +587,24 @@ static int tegra_tsensor_probe(struct platform_device= *pdev) return dev_err_probe(&pdev->dev, err, "failed to request interrupt\n"); =20 + /* + * Disable the interrupt so set_trips() can not be called + * while we are setting up the register + * TSENSOR_SENSOR0_CONFIG1. With this we close a potential + * race window where we are setting up the TH2 and the + * temperature hits TH1 resulting to an update of the + * TSENSOR_SENSOR0_CONFIG1 register in the ISR. + */ + disable_irq(irq); + for (i =3D 0; i < ARRAY_SIZE(ts->ch); i++) { err =3D tegra_tsensor_enable_hw_channel(ts, i); if (err) return err; } =20 + enable_irq(irq); + return 0; } =20 --=20 2.34.1