From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f196.google.com (mail-pl1-f196.google.com [209.85.214.196]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 145672857C9; Tue, 22 Apr 2025 15:26:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.196 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745335575; cv=none; b=ArJ22RByhhK18O4eVKGNvMm13PmvfOhde/ervBvyyzY89DOyBXjhW01R3kBgFvulE6mgrIyvFXjWwGmKoBkmf0x3o60kZhJOpNn0jtL7hDVAJFwy3+MEl/t/ZTeWXyCMRmUybvLED5RazT7jxd+FE9xZU1nUQzlKzbb0TCKDlEg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745335575; c=relaxed/simple; bh=V3EF+LAVoz+bP3kXGeKG/AH/Wx+8WltG6QBGmJY1phk=; h=Message-ID:Date:MIME-Version:Cc:Subject:To:References:From: In-Reply-To:Content-Type; b=YIyBehZsLoMJk/W2gGt/5Bg7Dh9Ab7S7jD9MXBzEMOyeKG9Z/tz0k0Mhu3t32/dvAjbWP4axlCubhvQ63qRaPYSornp+6QytU5AxOfveHN9c6DlN4j3QoLZcKAZ7bpUeB53atinqaxXVUevzU1r+dk6pyHD5yu1zxn47hLtoFbE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=UR1dT9vk; arc=none smtp.client-ip=209.85.214.196 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="UR1dT9vk" Received: by mail-pl1-f196.google.com with SMTP id d9443c01a7336-224191d92e4so52369065ad.3; Tue, 22 Apr 2025 08:26:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1745335573; x=1745940373; darn=vger.kernel.org; h=content-transfer-encoding:in-reply-to:from:content-language :references:to:subject:cc:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=Ky0slvl2m0Skj+7SoImzSsZ0KF7nAf3DtsbkUIFEsgs=; b=UR1dT9vkJo0+QbygmttEXYcBzfaY/ZKwF1vGB/KZxk9WeOUUEN1TvD8DXHvDxEzJP+ zk1IHJsObPESQ9LxWF/LGgwV40jmDhvPBh/+4IAhPAXnctLDoGxxE/z911KjRAn+yWrt g34AAf3g7NTw0+20zia5rP4EgThUwrJakme80096oTsq2OQj8SKUoKvJsck2snyAr4qS akRnmZnXQNvO8jNXkSbM3ZgLJ6Bf54c1Tr3ZX4otaj/4U1XwvZUpxqm4vhDaWRpOPKvS UWQau12dy07fzUNHqHeTXoveiDjgfYQHcWZkI+sVdITSNV1Cac6tmoVqENFFJ9MUJwTF Oczg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1745335573; x=1745940373; h=content-transfer-encoding:in-reply-to:from:content-language :references:to:subject:cc:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=Ky0slvl2m0Skj+7SoImzSsZ0KF7nAf3DtsbkUIFEsgs=; b=gBwpu2l7ghc+siOtoq02uY3w7PmTfD04zcX6qJP16mU8FaMTysBjxQJl/avLPjPcdp bSu2fjf0BCM5XRIoR4EUoKNXA/8aiVgQd+4oU5Ue8QfNqLXW0RaXQINY8B9h3yUlDfgb 1xgaagwCEWh0ZpgY833ef1yPPeDBZ34Fe7sgbMMn1Uww1nbHL2PV9RbS7/JkQj0/nwNn Rou5mXf9K2dLNbIk212CQgkNE1X9IUb8LVy9LcgYwdNe+sYHHI8WGYPK4NUu49UfZVfV Cv9o+8lzwk8TgYyyFty4poQBPDOJEvKrfWVS5Kckdqo9sz99yS4OC+hOzz8opDfufS2P 9HcA== X-Forwarded-Encrypted: i=1; AJvYcCVm8wW3zj60xJ8Vk78KNgw2tR62MyXztLO9igtWzoVs2Im9jvxJbg0ciTxpg4CRVDa+qmwhqgxQJd+HvWCP@vger.kernel.org, AJvYcCWKw4KGIeCvwJTh7z1hgOTOMQahuVHUOBBPd84e9EGFVOPu33lyZgO+uI1lj5GYFwa2rR/SvXCBrlk=@vger.kernel.org X-Gm-Message-State: AOJu0Yzm2nXv5wWwdv4MZtEMlf7L98say69Mdgz6atMMuhN/pmDRr5R8 2jk6SEA8JBJgJTZo02gfRC/oM7xPSoL1qcPjmpeiNnnlssTztZLL X-Gm-Gg: ASbGncuEeus7JaPbRRCUbFb1V5vcf74y9QAYuMow/jy1euFwTw3Bhyik0ZIeOVIvOE8 W6y2QmDJqEUgc3jDIDnpi58TVmMYSoKoi3gtn2uDyA3jYbA+QDE2lA3uViaGnLe/n/qlktn1f5X eAnusGcPfpR+c2NHL7fBDl3w/O+w/cchXOBbXWJKXUNIAcCmGu3y90u7/dSewlHQ9MU1QqA4dkE dIK178Vu1Wzk3LJ5UAJIsihoFwVLFEbw5odkOu4noZg3AYYkxbLbiFW5U47pD622H9EHkk0kY9U OSzrLYuLK0i02/f8YIwkyO/g/oxHaQ== X-Google-Smtp-Source: AGHT+IHYPLeKGWL1fyxBzXyLrmUfwx8HCx9qyTTP5pFdjq3MaUZ0+J0RZxkXJTfIv6je3bWU3Fj+qQ== X-Received: by 2002:a17:903:228a:b0:21f:5638:2d8 with SMTP id d9443c01a7336-22c53620bdfmr218015115ad.53.1745335572548; Tue, 22 Apr 2025 08:26:12 -0700 (PDT) Received: from [192.168.5.101] ([2602:f919:106::1b8]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-22c50bf16b1sm86663765ad.89.2025.04.22.08.26.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 22 Apr 2025 08:26:12 -0700 (PDT) Message-ID: <918e0177-8e26-405c-93ad-8b0d2dfd3b3d@gmail.com> Date: Tue, 22 Apr 2025 23:26:04 +0800 Precedence: bulk X-Mailing-List: linux-i2c@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Cc: troymitchell988@gmail.com, Oleksij Rempel , Pengutronix Kernel Team , Andi Shyti , Shawn Guo , Sascha Hauer , Fabio Estevam , linux-i2c@vger.kernel.org, imx@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Yongchao Jia Subject: Re: [PATCH 1/2] i2c: imx: use guard to take spinlock To: Jonathan Cameron References: <20250421-i2c-imx-update-v1-0-1137f1f353d5@gmail.com> <20250421-i2c-imx-update-v1-1-1137f1f353d5@gmail.com> <20250422161213.0000597d@huawei.com> Content-Language: en-US From: Troy Mitchell In-Reply-To: <20250422161213.0000597d@huawei.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 2025/4/22 23:12, Jonathan Cameron wrote: > On Mon, 21 Apr 2025 13:36:38 +0800 > Troy Mitchell wrote: > >> Use guard to automatically release the lock after going out of scope >> instead of calling it manually. > Drive by review, but this changes behavior in a subtle way so we > should have more commentary here... Thanks for your review! > >> Co-developed-by: Yongchao Jia >> Signed-off-by: Yongchao Jia >> Signed-off-by: Troy Mitchell >> --- >> drivers/i2c/busses/i2c-imx.c | 22 ++++++++++------------ >> 1 file changed, 10 insertions(+), 12 deletions(-) >> >> diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c >> index 9e5d454d8318..cb96a57df4a0 100644 >> --- a/drivers/i2c/busses/i2c-imx.c >> +++ b/drivers/i2c/busses/i2c-imx.c >> @@ -23,6 +23,7 @@ >> >> #include >> #include >> +#include >> #include >> #include >> #include >> >> @@ -1125,30 +1126,27 @@ static irqreturn_t i2c_imx_isr(int irq, void *dev_id) >> { >> struct imx_i2c_struct *i2c_imx = dev_id; >> unsigned int ctl, status; >> - unsigned long flags; >> >> - spin_lock_irqsave(&i2c_imx->slave_lock, flags); >> + guard(spinlock_irqsave)(&i2c_imx->slave_lock); >> + >> status = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2SR); >> ctl = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR); >> >> if (status & I2SR_IIF) { >> i2c_imx_clear_irq(i2c_imx, I2SR_IIF); >> + >> if (i2c_imx->slave) { >> if (!(ctl & I2CR_MSTA)) { >> irqreturn_t ret; >> >> - ret = i2c_imx_slave_handle(i2c_imx, >> - status, ctl); >> - spin_unlock_irqrestore(&i2c_imx->slave_lock, >> - flags); >> - return ret; >> + return i2c_imx_slave_handle(i2c_imx, >> + status, ctl); >> } >> i2c_imx_slave_finish_op(i2c_imx); >> } >> - spin_unlock_irqrestore(&i2c_imx->slave_lock, flags); > In this path the patch changes the lock release to occur after > i2c_imx_master_isr(i2c_imx, status); > > That may well be safe; I have no idea! You should talk about that > in the patch description if it is. You're correct that this change slightly alters the lock release timing. However, both i2c_imx_slave_handle() and i2c_imx_master_isr() can safely be entered with the lock held — there's no requirement for the lock to be released before calling them. Using guard(spinlock_irqsave) simplifies the control flow by ensuring consistent and automatic unlock, which improves readability without affecting correctness. I'll update the commit message to clarify this. > >> + >> return i2c_imx_master_isr(i2c_imx, status); >> } >> - spin_unlock_irqrestore(&i2c_imx->slave_lock, flags); >> >> return IRQ_NONE; >> } -- Troy Mitchell