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[2620:137:e000::1:20]) by mx.google.com with ESMTP id n21-20020a170906689500b008d2262654bdsi9516855ejr.430.2023.02.28.03.35.47; Tue, 28 Feb 2023 03:36:10 -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=@linaro.org header.s=google header.b=uH2iPKUi; 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=linaro.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231629AbjB1LZM (ORCPT + 99 others); Tue, 28 Feb 2023 06:25:12 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44892 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231637AbjB1LYU (ORCPT ); Tue, 28 Feb 2023 06:24:20 -0500 Received: from mail-wm1-x32c.google.com (mail-wm1-x32c.google.com [IPv6:2a00:1450:4864:20::32c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 44486241DC for ; Tue, 28 Feb 2023 03:23:46 -0800 (PST) Received: by mail-wm1-x32c.google.com with SMTP id l7-20020a05600c4f0700b003e79fa98ce1so5634436wmq.2 for ; Tue, 28 Feb 2023 03:23:46 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1677583419; 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=uH2iPKUi6WWzxncaaUCnNyUW93Te0pgpw5ZVwQslHbwqJ/8zYBAPRAyVU+rCYo49m+ vwJfjfzWSyZFyui3qDxrhI6YZtsgewelZDRzhfB/mrkRCN33zgfKv49GvwquHmeUuRCJ oywdKx2uiIdUmj6sohlH44EaXz6vKSFcPMgMQWRsWywfb8pKDToojlf05J6f+h16x1G9 6JZmgpLt5MkCIA68wsyWP+Oih9p+S27qOp9iIlRrA60IyxEzrB+RELqvhxCepoQtMy0W NDrdjdjoNPFlb3HS28boS3f6ksSeOu9s71kaooPyFE9PLqd2Vp6C26legnHfZg+ghuaL t6WA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1677583419; 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=2yP12XyBgSDs8M2+kNK0WBSe6V4QZmyWVXy1Ggxk0mY931lZiMmKep8vMAznWE9vQG xC6QybztU7GdURwYnMzQL/7wUhS5LMqwjl6bZQc7K8RhcF7cWYfj39P0A/6MTepp9cdK Q3y1HxO7ZhuSQjN2lGOWaYNP0Pp58M5vEsADpBXC3hHwFzZybFBzmgnWXJKXfazBkFBt AfOU2QQxmLrm9ICOL2HEoCiybK7CnvSbCYf1v4ubKrBR1tsurKNEbw/SxOJXvPSlJWe/ rmI7LdZfM0Z+/FhqeAV0AM1l9w/kcyiJFVFcvDCHnqDcpjpWI16GLZqKm621TdIxYHdZ MdbA== X-Gm-Message-State: AO0yUKWENEvQVjPAkEP4xNgh6ah0T2JVvNcJaOUZzuhUD1CmQvuptDmq YN6oGNBH856cMWJgUWOq3uEJqQ== X-Received: by 2002:a05:600c:4586:b0:3eb:376e:2ba5 with SMTP id r6-20020a05600c458600b003eb376e2ba5mr1823393wmo.3.1677583419590; Tue, 28 Feb 2023 03:23:39 -0800 (PST) Received: from mai.box.freepro.com ([2a05:6e02:1041:c10:6830:6390:2815:b6a5]) by smtp.gmail.com with ESMTPSA id z5-20020a5d6545000000b002c5501a5803sm9598130wrv.65.2023.02.28.03.23.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Feb 2023 03:23:39 -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 , Florian Fainelli , Jernej Skrabec , AngeloGioacchino Del Regno , =?utf-8?q?Niklas_S=C3=B6derlund?= , linux-tegra@vger.kernel.org (open list:TEGRA ARCHITECTURE SUPPORT) Subject: [PATCH v4 16/19] thermal/drivers/tegra: Remove unneeded lock when setting a trip point Date: Tue, 28 Feb 2023 12:22:35 +0100 Message-Id: <20230228112238.2312273-17-daniel.lezcano@linaro.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230228112238.2312273-1-daniel.lezcano@linaro.org> References: <20230228112238.2312273-1-daniel.lezcano@linaro.org> MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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?1759074499222340891?= X-GMAIL-MSGID: =?utf-8?q?1759074499222340891?= 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/tegra/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, tegra_tsensor_get_hw_channel_trips(tzd, &hot_trip, &crit_trip); - /* 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)); @@ -404,8 +401,6 @@ static int tegra_tsensor_enable_hw_channel(const struct tegra_tsensor *ts, val |= FIELD_PREP(TSENSOR_SENSOR0_CONFIG0_INTR_THERMAL_RST_EN, 1); writel_relaxed(val, tsc->regs + TSENSOR_SENSOR0_CONFIG0); - mutex_unlock(&tzd->lock); - err = 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"); + /* + * 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 = 0; i < ARRAY_SIZE(ts->ch); i++) { err = tegra_tsensor_enable_hw_channel(ts, i); if (err) return err; } + enable_irq(irq); + return 0; }