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Tue, 6 Apr 2021 11:49:32 +0000 Received: from localhost (172.20.145.6) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Tue, 6 Apr 2021 11:49:32 +0000 Date: Tue, 6 Apr 2021 13:50:03 +0200 From: Thierry Reding To: Pavel Machek CC: Greg Kroah-Hartman , , , Jonathan Hunter Subject: Re: [PATCH 5.10 079/126] drm/tegra: sor: Grab runtime PM reference across reset Message-ID: References: <20210405085031.040238881@linuxfoundation.org> <20210405085033.686284735@linuxfoundation.org> <20210405154221.GB305@amd> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="3BJ3eVQHxxGmMdDG" Content-Disposition: inline In-Reply-To: <20210405154221.GB305@amd> X-NVConfidentiality: public User-Agent: Mutt/2.0.6 (98f8cb83) (2021-03-06) X-Originating-IP: [172.20.145.6] X-ClientProxiedBy: HQMAIL101.nvidia.com (172.20.187.10) To HQMAIL107.nvidia.com (172.20.187.13) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: e6d9ad58-8dd6-43ff-ce22-08d8f8f20b4a X-MS-TrafficTypeDiagnostic: DM5PR12MB1259: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:9508; 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X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Apr 2021 11:49:32.7061 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: e6d9ad58-8dd6-43ff-ce22-08d8f8f20b4a X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.112.34];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: CO1NAM11FT008.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR12MB1259 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --3BJ3eVQHxxGmMdDG Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Apr 05, 2021 at 05:42:21PM +0200, Pavel Machek wrote: > Hi! >=20 > > However, these functions alone don't provide any guarantees at the > > system level. Drivers need to ensure that the only a single consumer has > > access to the reset at the same time. In order for the SOR to be able to > > exclusively access its reset, it must therefore ensure that the SOR > > power domain is not powered off by holding on to a runtime PM reference > > to that power domain across the reset assert/deassert operation. >=20 > Yeah, but it should not leak the PM reference in the error handling. True. However the only reason why the code could realistically fail between pm_runtime_resume_and_get() and pm_runtime_put() is if we did not take the runtime PM reference (which would cause the call to reset_control_acquire() to fail). So the chances of this actually leaking are practically zero, so I didn't want to bloat this bugfix with what's essentially dead code. I can queue up your fix below for v5.14, though, since it's obviously more correct from a theoretical point of view. 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