From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A33773BF30D; Wed, 21 Jan 2026 16:02:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769011378; cv=none; b=SkN8066w5/GUWAAfgI04JB01B+hBRtvph87ePUL/Q9S9btTe3Cc/YAsyq9vBrwjHF1f40mCqBannmyEqbqHvt8YYjQz3vKpexHukPD79c65zxDSe7OGmyRojistg7JKCkzbagP/Jl02nE1yn/KRY3x3coZHg4N/5iWEh5d1EsTA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769011378; c=relaxed/simple; bh=F9bPyEYde8jlWbcHshXKq3vOhM722s15C6Irbdet8y4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=OUTcnvIN6CwsfOj0KN02dXB2G9VxKZOHdPyQPmpYWbPy00vyV9WOX6Vg3zVxpqg0nAjdSiuj0fbgGXYjfbzxBDWP3W0cFvxX8uQ0us0wQSYtbUUcUYHJEFgmmQFpXcx1apDJ3j4ya6fXL7Irg8IIIRsIQeXLnN6N1+v09DFpDfc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=UEjgfzQ3; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="UEjgfzQ3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3F623C4CEF1; Wed, 21 Jan 2026 16:02:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1769011378; bh=F9bPyEYde8jlWbcHshXKq3vOhM722s15C6Irbdet8y4=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=UEjgfzQ3Yy0qFP25NRRt1WZG1cmk7k0VEnQyB8xip8s2J6UnYdkTSBrR1Yq5U5+uE 0/AMp8dQ8UaAL5vlNQGvE9xgYcRJVF0kJWMhmWCsTdQNmZVK9sqPcE4qTgwq9H8WSj +edWOKkfUP1XsY2kX/WO0nFvUK1NoTGdG+c5J/t7AK6agi9xolmIkOLVY+xnrq6eyI cR34/ZA8hz0wwyIEkWqCXlqQVA7JQ6csR+zf/w4CwHgQ8FI+Drz8Fh26vbcjxjMiep BGokjRjztegbw7pmQzjoicX9UM4NLWmZ7j6cw72innV0l4eFnts4DACl/UfmFE2gFl I9owkn1KBx8fg== Message-ID: <35780b65-8c95-4d58-8d4a-2f451cf5377d@kernel.org> Date: Wed, 21 Jan 2026 17:02:50 +0100 Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] iommu/arm-smmu-qcom: do not register driver in probe() To: Danilo Krummrich , gregkh@linuxfoundation.org, rafael@kernel.org, broonie@kernel.org, will@kernel.org, robin.murphy@arm.com, joro@8bytes.org, robin.clark@oss.qualcomm.com, hanguidong02@gmail.com, quic_c_gdjako@quicinc.com, dmitry.baryshkov@oss.qualcomm.com Cc: driver-core@lists.linux.dev, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev, linux-arm-msm@vger.kernel.org References: <20260121141215.29658-1-dakr@kernel.org> Content-Language: en-US From: Konrad Dybcio In-Reply-To: <20260121141215.29658-1-dakr@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 1/21/26 3:12 PM, Danilo Krummrich wrote: > Commit 0b4eeee2876f ("iommu/arm-smmu-qcom: Register the TBU driver in > qcom_smmu_impl_init") intended to also probe the TBU driver when > CONFIG_ARM_SMMU_QCOM_DEBUG is disabled, but also moved the corresponding > platform_driver_register() call into qcom_smmu_impl_init() which is > called from arm_smmu_device_probe(). > > However, it neither makes sense to register drivers from probe() > callbacks of other drivers, nor does the driver core allow registering > drivers with a device lock already being held. > > The latter was revealed by commit dc23806a7c47 ("driver core: enforce > device_lock for driver_match_device()") leading to a deadlock condition > described in [1]. > > Additionally, it was noted by Robin that the current approach is > potentially racy with async probe [2]. > > Hence, fix this by registering the qcom_smmu_tbu_driver from > module_init(). Unfortunately, due to the vendoring of the driver, this > requires an indirection through arm-smmu-impl.c. > > Reported-by: Mark Brown > Closes: https://lore.kernel.org/lkml/7ae38e31-ef31-43ad-9106-7c76ea0e8596@sirena.org.uk/ > Link: https://lore.kernel.org/lkml/DFU7CEPUSG9A.1KKGVW4HIPMSH@kernel.org/ [1] > Link: https://lore.kernel.org/lkml/0c0d3707-9ea5-44f9-88a1-a65c62e3df8d@arm.com/ [2] > Fixes: dc23806a7c47 ("driver core: enforce device_lock for driver_match_device()") > Fixes: 0b4eeee2876f ("iommu/arm-smmu-qcom: Register the TBU driver in qcom_smmu_impl_init") > Signed-off-by: Danilo Krummrich > --- Acked-by: Konrad Dybcio Konrad